tinycc/tccelf.c

/*
 *  ELF file handling for TCC
 *
 *  Copyright (c) 2001-2004 Fabrice Bellard
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "tcc.h"

/* Define this to get some debug output during relocation processing.  */
#undef DEBUG_RELOC

/********************************************************/
/* global variables */

ST_DATA Section *text_section, *data_section, *bss_section; /* predefined sections */
ST_DATA Section *cur_text_section; /* current section where function code is generated */
#ifdef CONFIG_TCC_ASM
ST_DATA Section *last_text_section; /* to handle .previous asm directive */
#endif
#ifdef CONFIG_TCC_BCHECK
/* bound check related sections */
ST_DATA Section *bounds_section; /* contains global data bound description */
ST_DATA Section *lbounds_section; /* contains local data bound description */
#endif
/* symbol sections */
ST_DATA Section *symtab_section, *strtab_section;
/* debug sections */
ST_DATA Section *stab_section, *stabstr_section;

/* XXX: avoid static variable */
static int new_undef_sym = 0; /* Is there a new undefined sym since last new_undef_sym() */

/* ------------------------------------------------------------------------- */

ST_FUNC void tccelf_new(TCCState *s)
{
    /* no section zero */
    dynarray_add((void ***)&s->sections, &s->nb_sections, NULL);

    /* create standard sections */
    text_section = new_section(s, ".text", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR);
    data_section = new_section(s, ".data", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
    bss_section = new_section(s, ".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);

    /* symbols are always generated for linking stage */
    symtab_section = new_symtab(s, ".symtab", SHT_SYMTAB, 0,
                                ".strtab",
                                ".hashtab", SHF_PRIVATE);
    strtab_section = symtab_section->link;
    s->symtab = symtab_section;

    /* private symbol table for dynamic symbols */
    s->dynsymtab_section = new_symtab(s, ".dynsymtab", SHT_SYMTAB, SHF_PRIVATE,
                                      ".dynstrtab",
                                      ".dynhashtab", SHF_PRIVATE);
}

#ifdef CONFIG_TCC_BCHECK
ST_FUNC void tccelf_bounds_new(TCCState *s)
{
    /* create bounds sections */
    bounds_section = new_section(s, ".bounds",
                                 SHT_PROGBITS, SHF_ALLOC);
    lbounds_section = new_section(s, ".lbounds",
                                  SHT_PROGBITS, SHF_ALLOC);
}
#endif

ST_FUNC void tccelf_stab_new(TCCState *s)
{
    stab_section = new_section(s, ".stab", SHT_PROGBITS, 0);
    stab_section->sh_entsize = sizeof(Stab_Sym);
    stabstr_section = new_section(s, ".stabstr", SHT_STRTAB, 0);
    put_elf_str(stabstr_section, "");
    stab_section->link = stabstr_section;
    /* put first entry */
    put_stabs("", 0, 0, 0, 0);
}

static void free_section(Section *s)
{
    tcc_free(s->data);
}

ST_FUNC void tccelf_delete(TCCState *s1)
{
    int i;

    /* free all sections */
    for(i = 1; i < s1->nb_sections; i++)
        free_section(s1->sections[i]);
    dynarray_reset(&s1->sections, &s1->nb_sections);

    for(i = 0; i < s1->nb_priv_sections; i++)
        free_section(s1->priv_sections[i]);
    dynarray_reset(&s1->priv_sections, &s1->nb_priv_sections);

    /* free any loaded DLLs */
#ifdef TCC_IS_NATIVE
    for ( i = 0; i < s1->nb_loaded_dlls; i++) {
        DLLReference *ref = s1->loaded_dlls[i];
        if ( ref->handle )
# ifdef _WIN32
            FreeLibrary((HMODULE)ref->handle);
# else
            dlclose(ref->handle);
# endif
    }
#endif
    /* free loaded dlls array */
    dynarray_reset(&s1->loaded_dlls, &s1->nb_loaded_dlls);
}

ST_FUNC Section *new_section(TCCState *s1, const char *name, int sh_type, int sh_flags)
{
    Section *sec;

    sec = tcc_mallocz(sizeof(Section) + strlen(name));
    strcpy(sec->name, name);
    sec->sh_type = sh_type;
    sec->sh_flags = sh_flags;
    switch(sh_type) {
    case SHT_HASH:
    case SHT_REL:
    case SHT_RELA:
    case SHT_DYNSYM:
    case SHT_SYMTAB:
    case SHT_DYNAMIC:
        sec->sh_addralign = 4;
        break;
    case SHT_STRTAB:
        sec->sh_addralign = 1;
        break;
    default:
        sec->sh_addralign =  PTR_SIZE; /* gcc/pcc default aligment */
        break;
    }

    if (sh_flags & SHF_PRIVATE) {
        dynarray_add((void ***)&s1->priv_sections, &s1->nb_priv_sections, sec);
    } else {
        sec->sh_num = s1->nb_sections;
        dynarray_add((void ***)&s1->sections, &s1->nb_sections, sec);
    }

    return sec;
}

/* realloc section and set its content to zero */
ST_FUNC void section_realloc(Section *sec, unsigned long new_size)
{
    unsigned long size;
    unsigned char *data;

    size = sec->data_allocated;
    if (size == 0)
        size = 1;
    while (size < new_size)
        size = size * 2;
    data = tcc_realloc(sec->data, size);
    memset(data + sec->data_allocated, 0, size - sec->data_allocated);
    sec->data = data;
    sec->data_allocated = size;
}

/* reserve at least 'size' bytes in section 'sec' from
   sec->data_offset. */
ST_FUNC void *section_ptr_add(Section *sec, addr_t size)
{
    size_t offset, offset1;

    offset = sec->data_offset;
    offset1 = offset + size;
    if (offset1 > sec->data_allocated)
        section_realloc(sec, offset1);
    sec->data_offset = offset1;
    return sec->data + offset;
}

/* reserve at least 'size' bytes from section start */
ST_FUNC void section_reserve(Section *sec, unsigned long size)
{
    if (size > sec->data_allocated)
        section_realloc(sec, size);
    if (size > sec->data_offset)
        sec->data_offset = size;
}

/* return a reference to a section, and create it if it does not
   exists */
ST_FUNC Section *find_section(TCCState *s1, const char *name)
{
    Section *sec;
    int i;
    for(i = 1; i < s1->nb_sections; i++) {
        sec = s1->sections[i];
        if (!strcmp(name, sec->name))
            return sec;
    }
    /* sections are created as PROGBITS */
    return new_section(s1, name, SHT_PROGBITS, SHF_ALLOC);
}

/* ------------------------------------------------------------------------- */

ST_FUNC int put_elf_str(Section *s, const char *sym)
{
    int offset, len;
    char *ptr;

    len = strlen(sym) + 1;
    offset = s->data_offset;
    ptr = section_ptr_add(s, len);
    memcpy(ptr, sym, len);
    return offset;
}

/* elf symbol hashing function */
static unsigned long elf_hash(const unsigned char *name)
{
    unsigned long h = 0, g;

    while (*name) {
        h = (h << 4) + *name++;
        g = h & 0xf0000000;
        if (g)
            h ^= g >> 24;
        h &= ~g;
    }
    return h;
}

/* rebuild hash table of section s */
/* NOTE: we do factorize the hash table code to go faster */
static void rebuild_hash(Section *s, unsigned int nb_buckets)
{
    ElfW(Sym) *sym;
    int *ptr, *hash, nb_syms, sym_index, h;
    unsigned char *strtab;

    strtab = s->link->data;
    nb_syms = s->data_offset / sizeof(ElfW(Sym));

    s->hash->data_offset = 0;
    ptr = section_ptr_add(s->hash, (2 + nb_buckets + nb_syms) * sizeof(int));
    ptr[0] = nb_buckets;
    ptr[1] = nb_syms;
    ptr += 2;
    hash = ptr;
    memset(hash, 0, (nb_buckets + 1) * sizeof(int));
    ptr += nb_buckets + 1;

    sym = (ElfW(Sym) *)s->data + 1;
    for(sym_index = 1; sym_index < nb_syms; sym_index++) {
        if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
            h = elf_hash(strtab + sym->st_name) % nb_buckets;
            *ptr = hash[h];
            hash[h] = sym_index;
        } else {
            *ptr = 0;
        }
        ptr++;
        sym++;
    }
}

/* return the symbol number */
ST_FUNC int put_elf_sym(Section *s, addr_t value, unsigned long size,
    int info, int other, int shndx, const char *name)
{
    int name_offset, sym_index;
    int nbuckets, h;
    ElfW(Sym) *sym;
    Section *hs;

    sym = section_ptr_add(s, sizeof(ElfW(Sym)));
    if (name)
        name_offset = put_elf_str(s->link, name);
    else
        name_offset = 0;
    /* XXX: endianness */
    sym->st_name = name_offset;
    sym->st_value = value;
    sym->st_size = size;
    sym->st_info = info;
    sym->st_other = other;
    sym->st_shndx = shndx;
    sym_index = sym - (ElfW(Sym) *)s->data;
    hs = s->hash;
    if (hs) {
        int *ptr, *base;
        ptr = section_ptr_add(hs, sizeof(int));
        base = (int *)hs->data;
        /* only add global or weak symbols */
        if (ELFW(ST_BIND)(info) != STB_LOCAL) {
            /* add another hashing entry */
            nbuckets = base[0];
            h = elf_hash((unsigned char *) name) % nbuckets;
            *ptr = base[2 + h];
            base[2 + h] = sym_index;
            base[1]++;
            /* we resize the hash table */
            hs->nb_hashed_syms++;
            if (hs->nb_hashed_syms > 2 * nbuckets) {
                rebuild_hash(s, 2 * nbuckets);
            }
        } else {
            *ptr = 0;
            base[1]++;
        }
    }
    return sym_index;
}

/* find global ELF symbol 'name' and return its index. Return 0 if not
   found. */
ST_FUNC int find_elf_sym(Section *s, const char *name)
{
    ElfW(Sym) *sym;
    Section *hs;
    int nbuckets, sym_index, h;
    const char *name1;

    hs = s->hash;
    if (!hs)
        return 0;
    nbuckets = ((int *)hs->data)[0];
    h = elf_hash((unsigned char *) name) % nbuckets;
    sym_index = ((int *)hs->data)[2 + h];
    while (sym_index != 0) {
        sym = &((ElfW(Sym) *)s->data)[sym_index];
        name1 = (char *) s->link->data + sym->st_name;
        if (!strcmp(name, name1))
            return sym_index;
        sym_index = ((int *)hs->data)[2 + nbuckets + sym_index];
    }
    return 0;
}

/* return elf symbol value, signal error if 'err' is nonzero */
ST_FUNC addr_t get_elf_sym_addr(TCCState *s, const char *name, int err)
{
    int sym_index;
    ElfW(Sym) *sym;

    sym_index = find_elf_sym(s->symtab, name);
    sym = &((ElfW(Sym) *)s->symtab->data)[sym_index];
    if (!sym_index || sym->st_shndx == SHN_UNDEF) {
        if (err)
            tcc_error("%s not defined", name);
        return 0;
    }
    return sym->st_value;
}

/* return elf symbol value */
LIBTCCAPI void *tcc_get_symbol(TCCState *s, const char *name)
{
    return (void*)(uintptr_t)get_elf_sym_addr(s, name, 0);
}

#if defined TCC_IS_NATIVE || defined TCC_TARGET_PE
/* return elf symbol value or error */
ST_FUNC void* tcc_get_symbol_err(TCCState *s, const char *name)
{
    return (void*)(uintptr_t)get_elf_sym_addr(s, name, 1);
}
#endif

/* add an elf symbol : check if it is already defined and patch
   it. Return symbol index. NOTE that sh_num can be SHN_UNDEF. */
ST_FUNC int set_elf_sym(Section *s, addr_t value, unsigned long size,
                       int info, int other, int shndx, const char *name)
{
    ElfW(Sym) *esym;
    int sym_bind, sym_index, sym_type, esym_bind;
    unsigned char sym_vis, esym_vis, new_vis;

    sym_bind = ELFW(ST_BIND)(info);
    sym_type = ELFW(ST_TYPE)(info);
    sym_vis = ELFW(ST_VISIBILITY)(other);

    sym_index = find_elf_sym(s, name);
    esym = &((ElfW(Sym) *)s->data)[sym_index];
    if (sym_index && esym->st_value == value && esym->st_size == size
	&& esym->st_info == info && esym->st_other == other
	&& esym->st_shndx == shndx)
        return sym_index;

    if (sym_bind != STB_LOCAL) {
        /* we search global or weak symbols */
        if (!sym_index)
            goto do_def;
        if (esym->st_shndx != SHN_UNDEF) {
            esym_bind = ELFW(ST_BIND)(esym->st_info);
            /* propagate the most constraining visibility */
            /* STV_DEFAULT(0)<STV_PROTECTED(3)<STV_HIDDEN(2)<STV_INTERNAL(1) */
            esym_vis = ELFW(ST_VISIBILITY)(esym->st_other);
            if (esym_vis == STV_DEFAULT) {
                new_vis = sym_vis;
            } else if (sym_vis == STV_DEFAULT) {
                new_vis = esym_vis;
            } else {
                new_vis = (esym_vis < sym_vis) ? esym_vis : sym_vis;
            }
            esym->st_other = (esym->st_other & ~ELFW(ST_VISIBILITY)(-1))
                             | new_vis;
            other = esym->st_other; /* in case we have to patch esym */
            if (shndx == SHN_UNDEF) {
                /* ignore adding of undefined symbol if the
                   corresponding symbol is already defined */
            } else if (sym_bind == STB_GLOBAL && esym_bind == STB_WEAK) {
                /* global overrides weak, so patch */
                goto do_patch;
            } else if (sym_bind == STB_WEAK && esym_bind == STB_GLOBAL) {
                /* weak is ignored if already global */
            } else if (sym_bind == STB_WEAK && esym_bind == STB_WEAK) {
                /* keep first-found weak definition, ignore subsequents */
            } else if (sym_vis == STV_HIDDEN || sym_vis == STV_INTERNAL) {
                /* ignore hidden symbols after */
            } else if ((esym->st_shndx == SHN_COMMON
                            || esym->st_shndx == bss_section->sh_num)
                        && (shndx < SHN_LORESERVE
                            && shndx != bss_section->sh_num)) {
                /* data symbol gets precedence over common/bss */
                goto do_patch;
            } else if (shndx == SHN_COMMON || shndx == bss_section->sh_num) {
                /* data symbol keeps precedence over common/bss */
            } else if (s == tcc_state->dynsymtab_section) {
                /* we accept that two DLL define the same symbol */
            } else {
#if 0
                printf("new_bind=%x new_shndx=%x new_vis=%x old_bind=%x old_shndx=%x old_vis=%x\n",
                       sym_bind, shndx, new_vis, esym_bind, esym->st_shndx, esym_vis);
#endif
                tcc_error_noabort("'%s' defined twice", name);
            }
        } else {
        do_patch:
            esym->st_info = ELFW(ST_INFO)(sym_bind, sym_type);
            esym->st_shndx = shndx;
            new_undef_sym = 1;
            esym->st_value = value;
            esym->st_size = size;
            esym->st_other = other;
        }
    } else {
    do_def:
        sym_index = put_elf_sym(s, value, size,
                                ELFW(ST_INFO)(sym_bind, sym_type), other,
                                shndx, name);
    }
    return sym_index;
}

/* put relocation */
ST_FUNC void put_elf_reloca(Section *symtab, Section *s, unsigned long offset,
                            int type, int symbol, addr_t addend)
{
    char buf[256];
    Section *sr;
    ElfW_Rel *rel;

    sr = s->reloc;
    if (!sr) {
        /* if no relocation section, create it */
        snprintf(buf, sizeof(buf), REL_SECTION_FMT, s->name);
        /* if the symtab is allocated, then we consider the relocation
           are also */
        sr = new_section(tcc_state, buf, SHT_RELX, symtab->sh_flags);
        sr->sh_entsize = sizeof(ElfW_Rel);
        sr->link = symtab;
        sr->sh_info = s->sh_num;
        s->reloc = sr;
    }
    rel = section_ptr_add(sr, sizeof(ElfW_Rel));
    rel->r_offset = offset;
    rel->r_info = ELFW(R_INFO)(symbol, type);
#if defined(TCC_TARGET_ARM64) || defined(TCC_TARGET_X86_64)
    rel->r_addend = addend;
#else
    if (addend)
        tcc_error("non-zero addend on REL architecture");
#endif
}

ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
                           int type, int symbol)
{
    put_elf_reloca(symtab, s, offset, type, symbol, 0);
}

/* put stab debug information */

ST_FUNC void put_stabs(const char *str, int type, int other, int desc,
                      unsigned long value)
{
    Stab_Sym *sym;

    sym = section_ptr_add(stab_section, sizeof(Stab_Sym));
    if (str) {
        sym->n_strx = put_elf_str(stabstr_section, str);
    } else {
        sym->n_strx = 0;
    }
    sym->n_type = type;
    sym->n_other = other;
    sym->n_desc = desc;
    sym->n_value = value;
}

ST_FUNC void put_stabs_r(const char *str, int type, int other, int desc,
                        unsigned long value, Section *sec, int sym_index)
{
    put_stabs(str, type, other, desc, value);
    put_elf_reloc(symtab_section, stab_section,
                  stab_section->data_offset - sizeof(unsigned int),
                  R_DATA_32, sym_index);
}

ST_FUNC void put_stabn(int type, int other, int desc, int value)
{
    put_stabs(NULL, type, other, desc, value);
}

ST_FUNC void put_stabd(int type, int other, int desc)
{
    put_stabs(NULL, type, other, desc, 0);
}

static struct sym_attr *get_sym_attr(TCCState *s1, int index, int alloc)
{
    int n;
    struct sym_attr *tab;

    if (index >= s1->nb_sym_attrs) {
        if (!alloc)
            return NULL;
        /* find immediately bigger power of 2 and reallocate array */
        n = 1;
        while (index >= n)
            n *= 2;
        tab = tcc_realloc(s1->sym_attrs, n * sizeof(*s1->sym_attrs));
        s1->sym_attrs = tab;
        memset(s1->sym_attrs + s1->nb_sym_attrs, 0,
               (n - s1->nb_sym_attrs) * sizeof(*s1->sym_attrs));
        s1->nb_sym_attrs = n;
    }
    return &s1->sym_attrs[index];
}

/* Browse each elem of type <type> in section <sec> starting at elem <startoff>
   using variable <elem> */
#define for_each_elem(sec, startoff, elem, type) \
    for (elem = (type *) sec->data + startoff; \
         elem < (type *) (sec->data + sec->data_offset); elem++)

/* In an ELF file symbol table, the local symbols must appear below
   the global and weak ones. Since TCC cannot sort it while generating
   the code, we must do it after. All the relocation tables are also
   modified to take into account the symbol table sorting */
static void sort_syms(TCCState *s1, Section *s)
{
    int *old_to_new_syms;
    ElfW(Sym) *new_syms;
    int nb_syms, i;
    ElfW(Sym) *p, *q;
    ElfW_Rel *rel;
    Section *sr;
    int type, sym_index;

    nb_syms = s->data_offset / sizeof(ElfW(Sym));
    new_syms = tcc_malloc(nb_syms * sizeof(ElfW(Sym)));
    old_to_new_syms = tcc_malloc(nb_syms * sizeof(int));

    /* first pass for local symbols */
    p = (ElfW(Sym) *)s->data;
    q = new_syms;
    for(i = 0; i < nb_syms; i++) {
        if (ELFW(ST_BIND)(p->st_info) == STB_LOCAL) {
            old_to_new_syms[i] = q - new_syms;
            *q++ = *p;
        }
        p++;
    }
    /* save the number of local symbols in section header */
    s->sh_info = q - new_syms;

    /* then second pass for non local symbols */
    p = (ElfW(Sym) *)s->data;
    for(i = 0; i < nb_syms; i++) {
        if (ELFW(ST_BIND)(p->st_info) != STB_LOCAL) {
            old_to_new_syms[i] = q - new_syms;
            *q++ = *p;
        }
        p++;
    }

    /* we copy the new symbols to the old */
    memcpy(s->data, new_syms, nb_syms * sizeof(ElfW(Sym)));
    tcc_free(new_syms);

    /* now we modify all the relocations */
    for(i = 1; i < s1->nb_sections; i++) {
        sr = s1->sections[i];
        if (sr->sh_type == SHT_RELX && sr->link == s) {
            for_each_elem(sr, 0, rel, ElfW_Rel) {
                sym_index = ELFW(R_SYM)(rel->r_info);
                type = ELFW(R_TYPE)(rel->r_info);
                sym_index = old_to_new_syms[sym_index];
                rel->r_info = ELFW(R_INFO)(sym_index, type);
            }
        }
    }

    tcc_free(old_to_new_syms);
}

/* relocate common symbols in the .bss section */
ST_FUNC void relocate_common_syms(void)
{
    ElfW(Sym) *sym;
    unsigned long offset, align;

    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        if (sym->st_shndx == SHN_COMMON) {
            /* align symbol */
            align = sym->st_value;
            offset = bss_section->data_offset;
            offset = (offset + align - 1) & -align;
            sym->st_value = offset;
            sym->st_shndx = bss_section->sh_num;
            offset += sym->st_size;
            bss_section->data_offset = offset;
        }
    }
}

/* relocate symbol table, resolve undefined symbols if do_resolve is
   true and output error if undefined symbol. */
ST_FUNC void relocate_syms(TCCState *s1, int do_resolve)
{
    ElfW(Sym) *sym;
    int sym_bind, sh_num;
    const char *name;

    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        sh_num = sym->st_shndx;
        if (sh_num == SHN_UNDEF) {
            name = (char *) strtab_section->data + sym->st_name;
            /* Use ld.so to resolve symbol for us (for tcc -run) */
            if (do_resolve) {
#if defined TCC_IS_NATIVE && !defined TCC_TARGET_PE
                void *addr;
                name = (char *) symtab_section->link->data + sym->st_name;
                addr = dlsym(RTLD_DEFAULT, name);
                if (addr) {
                    sym->st_value = (addr_t)addr;
#ifdef DEBUG_RELOC
		    printf ("relocate_sym: %s -> 0x%lx\n", name, sym->st_value);
#endif
                    goto found;
                }
#endif
            /* if dynamic symbol exist, it will be used in relocate_section */
            } else if (s1->dynsym && find_elf_sym(s1->dynsym, name))
                goto found;
            /* XXX: _fp_hw seems to be part of the ABI, so we ignore
               it */
            if (!strcmp(name, "_fp_hw"))
                goto found;
            /* only weak symbols are accepted to be undefined. Their
               value is zero */
            sym_bind = ELFW(ST_BIND)(sym->st_info);
            if (sym_bind == STB_WEAK) {
                sym->st_value = 0;
            } else {
                tcc_error_noabort("undefined symbol '%s'", name);
            }
        } else if (sh_num < SHN_LORESERVE) {
            /* add section base */
            sym->st_value += s1->sections[sym->st_shndx]->sh_addr;
        }
    found: ;
    }
}

/* relocate a given section (CPU dependent) by applying the relocations
   in the associated relocation section */
ST_FUNC void relocate_section(TCCState *s1, Section *s)
{
    Section *sr = s->reloc;
    ElfW_Rel *rel;
    ElfW(Sym) *sym;
    int type, sym_index;
    unsigned char *ptr;
    addr_t tgt, addr;
    struct sym_attr *symattr;

    relocate_init(sr);
    for_each_elem(sr, 0, rel, ElfW_Rel) {
        ptr = s->data + rel->r_offset;

        sym_index = ELFW(R_SYM)(rel->r_info);
        sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
        type = ELFW(R_TYPE)(rel->r_info);
        symattr = get_sym_attr(s1, sym_index, 0);
        tgt = sym->st_value;
	/* If static relocation to a dynamic symbol, relocate to PLT entry.
           Note 1: in tcc -run mode we go through PLT to avoid range issues
           Note 2: symbols compiled with libtcc and later added with
           tcc_add_symbol are not dynamic and thus have symattr NULL */
        if (relocs_info[type].gotplt_entry != NO_GOTPLT_ENTRY &&
            relocs_info[type].code_reloc && symattr && symattr->plt_offset)
            tgt = s1->plt->sh_addr + symattr->plt_offset;
#if defined(TCC_TARGET_ARM64) || defined(TCC_TARGET_X86_64)
        tgt += rel->r_addend;
#endif
        addr = s->sh_addr + rel->r_offset;

	relocate(s1, rel, type, ptr, addr, tgt);
    }
    /* if the relocation is allocated, we change its symbol table */
    if (sr->sh_flags & SHF_ALLOC)
        sr->link = s1->dynsym;
}

/* relocate relocation table in 'sr' */
static void relocate_rel(TCCState *s1, Section *sr)
{
    Section *s;
    ElfW_Rel *rel;

    s = s1->sections[sr->sh_info];
    for_each_elem(sr, 0, rel, ElfW_Rel)
        rel->r_offset += s->sh_addr;
}

/* count the number of dynamic relocations so that we can reserve
   their space */
static int prepare_dynamic_rel(TCCState *s1, Section *sr)
{
    ElfW_Rel *rel;
    int sym_index, esym_index, type, count;

    count = 0;
    for_each_elem(sr, 0, rel, ElfW_Rel) {
        sym_index = ELFW(R_SYM)(rel->r_info);
        type = ELFW(R_TYPE)(rel->r_info);
        switch(type) {
#if defined(TCC_TARGET_I386)
        case R_386_32:
#elif defined(TCC_TARGET_X86_64)
        case R_X86_64_32:
        case R_X86_64_32S:
        case R_X86_64_64:
#endif
            count++;
            break;
#if defined(TCC_TARGET_I386)
        case R_386_PC32:
#elif defined(TCC_TARGET_X86_64)
        case R_X86_64_PC32:
#endif
            esym_index = s1->symtab_to_dynsym[sym_index];
            if (esym_index)
                count++;
            break;
        default:
            break;
        }
    }
    if (count) {
        /* allocate the section */
        sr->sh_flags |= SHF_ALLOC;
        sr->sh_size = count * sizeof(ElfW_Rel);
    }
    return count;
}

static void build_got(TCCState *s1)
{
    unsigned char *ptr;

    /* if no got, then create it */
    s1->got = new_section(s1, ".got", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
    s1->got->sh_entsize = 4;
    set_elf_sym(symtab_section, 0, 4, ELFW(ST_INFO)(STB_GLOBAL, STT_OBJECT),
                0, s1->got->sh_num, "_GLOBAL_OFFSET_TABLE_");
    ptr = section_ptr_add(s1->got, 3 * PTR_SIZE);
#if PTR_SIZE == 4
    /* keep space for _DYNAMIC pointer, if present */
    write32le(ptr, 0);
    /* two dummy got entries */
    write32le(ptr + 4, 0);
    write32le(ptr + 8, 0);
#else
    /* keep space for _DYNAMIC pointer, if present */
    write32le(ptr, 0);
    write32le(ptr + 4, 0);
    /* two dummy got entries */
    write32le(ptr + 8, 0);
    write32le(ptr + 12, 0);
    write32le(ptr + 16, 0);
    write32le(ptr + 20, 0);
#endif
}

/* Create a GOT and (for function call) a PLT entry corresponding to a symbol
   in s1->symtab. When creating the dynamic symbol table entry for the GOT
   relocation, use 'size' and 'info' for the corresponding symbol metadata.
   Returns the offset of the GOT or (if any) PLT entry. */
static unsigned long put_got_entry(TCCState *s1, int dyn_reloc_type,
                                   int reloc_type, unsigned long size,
                                   int info, int sym_index)
{
    int index, need_plt_entry = 0;
    const char *name;
    ElfW(Sym) *sym, *esym;
    unsigned long offset;
    int *ptr;
    size_t got_offset;
    struct sym_attr *symattr;

    need_plt_entry = (dyn_reloc_type == R_JMP_SLOT);

    if (!s1->got)
        build_got(s1);

    /* create PLT if needed */
    if (need_plt_entry && !s1->plt) {
	s1->plt = new_section(s1, ".plt", SHT_PROGBITS,
			      SHF_ALLOC | SHF_EXECINSTR);
	s1->plt->sh_entsize = 4;
    }

    /* already a GOT and/or PLT entry, no need to add one */
    if (sym_index < s1->nb_sym_attrs) {
	if (need_plt_entry && s1->sym_attrs[sym_index].plt_offset)
	  return s1->sym_attrs[sym_index].plt_offset;
	else if (!need_plt_entry && s1->sym_attrs[sym_index].got_offset)
	  return s1->sym_attrs[sym_index].got_offset;
    }

    symattr = get_sym_attr(s1, sym_index, 1);

    /* create the GOT entry */
    ptr = section_ptr_add(s1->got, PTR_SIZE);
    *ptr = 0;
    got_offset = OFFSET_FROM_SECTION_START (s1->got, ptr);

    /* In case a function is both called and its address taken 2 GOT entries
       are created, one for taking the address (GOT) and the other for the PLT
       entry (PLTGOT). We don't record the offset of the PLTGOT entry in the
       got_offset field since it might overwrite the offset of a GOT entry.
       Besides, for PLT entry the static relocation is against the PLT entry
       and the dynamic relocation for PLTGOT is created in this function. */
    if (!need_plt_entry)
        symattr->got_offset = got_offset;

    sym = &((ElfW(Sym) *) symtab_section->data)[sym_index];
    name = (char *) symtab_section->link->data + sym->st_name;
    offset = sym->st_value;

    /* create PLT entry */
    if (need_plt_entry) {
#if defined(TCC_TARGET_I386) || defined(TCC_TARGET_X86_64)
        Section *plt;
        uint8_t *p;
        int modrm;
        unsigned long relofs;

#if defined(TCC_OUTPUT_DLL_WITH_PLT)
        modrm = 0x25;
#else
        /* if we build a DLL, we add a %ebx offset */
        if (s1->output_type == TCC_OUTPUT_DLL)
            modrm = 0xa3;
        else
            modrm = 0x25;
#endif

        plt = s1->plt;
        /* empty PLT: create PLT0 entry that pushes the library indentifier
           (GOT + PTR_SIZE) and jumps to ld.so resolution routine
           (GOT + 2 * PTR_SIZE) */
        if (plt->data_offset == 0) {
            p = section_ptr_add(plt, 16);
            p[0] = 0xff; /* pushl got + PTR_SIZE */
            p[1] = modrm + 0x10;
            write32le(p + 2, PTR_SIZE);
            p[6] = 0xff; /* jmp *(got + PTR_SIZE * 2) */
            p[7] = modrm;
            write32le(p + 8, PTR_SIZE * 2);
        }

        /* The PLT slot refers to the relocation entry it needs via offset.
           The reloc entry is created below, so its offset is the current
           data_offset */
        relofs = s1->got->reloc ? s1->got->reloc->data_offset : 0;
        symattr->plt_offset = plt->data_offset;

        /* Jump to GOT entry where ld.so initially put the address of ip + 4 */
        p = section_ptr_add(plt, 16);
        p[0] = 0xff; /* jmp *(got + x) */
        p[1] = modrm;
        write32le(p + 2, got_offset);
        p[6] = 0x68; /* push $xxx */
#ifdef TCC_TARGET_X86_64
	/* On x86-64, the relocation is referred to by _index_ */
        write32le(p + 7, relofs / sizeof (ElfW_Rel));
#else
        write32le(p + 7, relofs);
#endif
        p[11] = 0xe9; /* jmp plt_start */
        write32le(p + 12, -(plt->data_offset));

        /* If this was an UNDEF symbol set the offset in the dynsymtab to the
           PLT slot, so that PC32 relocs to it can be resolved */
        if (sym->st_shndx == SHN_UNDEF)
            offset = plt->data_offset - 16;
#elif defined(TCC_TARGET_ARM)
        Section *plt;
        uint8_t *p;

        /* when building a DLL, GOT entry accesses must be done relative to
           start of GOT (see x86_64 examble above)  */
        if (s1->output_type == TCC_OUTPUT_DLL)
            tcc_error("DLLs unimplemented!");

        plt = s1->plt;
        /* empty PLT: create PLT0 entry that push address of call site and
           jump to ld.so resolution routine (GOT + 8) */
        if (plt->data_offset == 0) {
            p = section_ptr_add(plt, 20);
            write32le(p,    0xe52de004); /* push {lr}         */
            write32le(p+4,  0xe59fe004); /* ldr lr, [pc, #4] */
            write32le(p+8,  0xe08fe00e); /* add lr, pc, lr    */
            write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
            /* p+16 is set in relocate_plt */
        }

        symattr->plt_offset = plt->data_offset;
        if (symattr->plt_thumb_stub) {
            p = section_ptr_add(plt, 4);
            write32le(p,   0x4778); /* bx pc */
            write32le(p+2, 0x46c0); /* nop   */
        }
        p = section_ptr_add(plt, 16);
        /* Jump to GOT entry where ld.so initially put address of PLT0 */
        write32le(p,   0xe59fc004); /* ldr ip, [pc, #4] */
        write32le(p+4, 0xe08fc00c); /* add ip, pc, ip */
        write32le(p+8, 0xe59cf000); /* ldr pc, [ip] */
	/* p + 12 contains offset to GOT entry once patched by relocate_plt */
        write32le(p+12, got_offset);

        /* the symbol is modified so that it will be relocated to the PLT */
	if (sym->st_shndx == SHN_UNDEF)
            offset = plt->data_offset - 16;
#elif defined(TCC_TARGET_ARM64)
        Section *plt;
        uint8_t *p;

        if (s1->output_type == TCC_OUTPUT_DLL)
            tcc_error("DLLs unimplemented!");

        plt = s1->plt;
        if (plt->data_offset == 0)
            section_ptr_add(plt, 32);
        symattr->plt_offset = plt->data_offset;
        p = section_ptr_add(plt, 16);
        write32le(p, got_offset);
        write32le(p + 4, (uint64_t) got_offset >> 32);

        if (sym->st_shndx == SHN_UNDEF)
            offset = plt->data_offset - 16;
#elif defined(TCC_TARGET_C67)
        tcc_error("C67 got not implemented");
#else
#error unsupported CPU
#endif
    }

    /* Create the GOT relocation that will insert the address of the object or
       function of interest in the GOT entry. This is a static relocation for
       memory output (dlsym will give us the address of symbols) and dynamic
       relocation otherwise (executable and DLLs). The relocation should be
       done lazily for GOT entry with *_JUMP_SLOT relocation type (the one
       associated to a PLT entry) but is currently done at load time for an
       unknown reason. */
    if (s1->dynsym) {
        /* create the dynamic symbol table entry that the relocation refers to
           in its r_info field to identify the symbol */
	/* XXX This might generate multiple syms for name.  */
        index = find_elf_sym (s1->dynsym, name);
        if (index) {
            esym = (ElfW(Sym) *) s1->dynsym->data + index;
            esym->st_value = offset;

        } else if (s1->output_type == TCC_OUTPUT_MEMORY ||
                   relocs_info[reloc_type].gotplt_entry == ALWAYS_GOTPLT_ENTRY)
            index = put_elf_sym(s1->dynsym, offset, size, info, 0,
                                sym->st_shndx, name);
        put_elf_reloc(s1->dynsym, s1->got, got_offset, dyn_reloc_type, index);
    } else
	put_elf_reloc(symtab_section, s1->got, got_offset, dyn_reloc_type,
                      sym_index);

    if (need_plt_entry)
      return symattr->plt_offset;
    else
      return symattr->got_offset;
}

/* build GOT and PLT entries */
ST_FUNC void build_got_entries(TCCState *s1)
{
    Section *s;
    ElfW_Rel *rel;
    ElfW(Sym) *sym;
    int i, type, reloc_type, sym_index;

    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type != SHT_RELX)
            continue;
        /* no need to handle got relocations */
        if (s->link != symtab_section)
            continue;
        for_each_elem(s, 0, rel, ElfW_Rel) {
            type = ELFW(R_TYPE)(rel->r_info);
            sym_index = ELFW(R_SYM)(rel->r_info);
            sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
            if (relocs_info[type].gotplt_entry == NO_GOTPLT_ENTRY)
                continue;

            /* Proceed with PLT/GOT [entry] creation if any of the following
               condition is met:
               - it is an undefined reference (dynamic relocation needed)
               - symbol is absolute (probably created by tcc_add_symbol)
               - relocation requires a PLT/GOT (BUILD_GOTPLT_ENTRY or
                 ALWAYS_GOTPLT_ENTRY). */
            if (sym->st_shndx != SHN_UNDEF &&
                sym->st_shndx != SHN_ABS &&
                relocs_info[type].gotplt_entry == AUTO_GOTPLT_ENTRY)
                continue;

#ifdef TCC_TARGET_X86_64
            if (type == R_X86_64_PLT32 &&
                ELFW(ST_VISIBILITY)(sym->st_other) != STV_DEFAULT) {
                rel->r_info = ELFW(R_INFO)(sym_index, R_X86_64_PC32);
                continue;
            }
#endif

            if (!s1->got)
                build_got(s1);

            if (relocs_info[type].gotplt_entry == BUILD_GOT_ONLY)
                continue;

            if (relocs_info[type].code_reloc)
                reloc_type = R_JMP_SLOT;
            else
                reloc_type = R_GLOB_DAT;
            put_got_entry(s1, reloc_type, type, sym->st_size, sym->st_info,
                          sym_index);
        }
    }
}

ST_FUNC Section *new_symtab(TCCState *s1,
                           const char *symtab_name, int sh_type, int sh_flags,
                           const char *strtab_name,
                           const char *hash_name, int hash_sh_flags)
{
    Section *symtab, *strtab, *hash;
    int *ptr, nb_buckets;

    symtab = new_section(s1, symtab_name, sh_type, sh_flags);
    symtab->sh_entsize = sizeof(ElfW(Sym));
    strtab = new_section(s1, strtab_name, SHT_STRTAB, sh_flags);
    put_elf_str(strtab, "");
    symtab->link = strtab;
    put_elf_sym(symtab, 0, 0, 0, 0, 0, NULL);

    nb_buckets = 1;

    hash = new_section(s1, hash_name, SHT_HASH, hash_sh_flags);
    hash->sh_entsize = sizeof(int);
    symtab->hash = hash;
    hash->link = symtab;

    ptr = section_ptr_add(hash, (2 + nb_buckets + 1) * sizeof(int));
    ptr[0] = nb_buckets;
    ptr[1] = 1;
    memset(ptr + 2, 0, (nb_buckets + 1) * sizeof(int));
    return symtab;
}

/* put dynamic tag */
static void put_dt(Section *dynamic, int dt, addr_t val)
{
    ElfW(Dyn) *dyn;
    dyn = section_ptr_add(dynamic, sizeof(ElfW(Dyn)));
    dyn->d_tag = dt;
    dyn->d_un.d_val = val;
}

#ifndef TCC_TARGET_PE
static void add_init_array_defines(TCCState *s1, const char *section_name)
{
    Section *s;
    long end_offset;
    char sym_start[1024];
    char sym_end[1024];

    snprintf(sym_start, sizeof(sym_start), "__%s_start", section_name + 1);
    snprintf(sym_end, sizeof(sym_end), "__%s_end", section_name + 1);

    s = find_section(s1, section_name);
    if (!s) {
        end_offset = 0;
        s = data_section;
    } else {
        end_offset = s->data_offset;
    }

    set_elf_sym(symtab_section,
                0, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                s->sh_num, sym_start);
    set_elf_sym(symtab_section,
                end_offset, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                s->sh_num, sym_end);
}
#endif

static int tcc_add_support(TCCState *s1, const char *filename)
{
    char buf[1024];
    snprintf(buf, sizeof(buf), "%s/"TCC_ARCH_DIR"%s", s1->tcc_lib_path, filename);
    return tcc_add_file(s1, buf);
}

ST_FUNC void tcc_add_bcheck(TCCState *s1)
{
#ifdef CONFIG_TCC_BCHECK
    addr_t *ptr;
    int sym_index;

    if (0 == s1->do_bounds_check)
        return;
    /* XXX: add an object file to do that */
    ptr = section_ptr_add(bounds_section, sizeof(*ptr));
    *ptr = 0;
    set_elf_sym(symtab_section, 0, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                bounds_section->sh_num, "__bounds_start");
    /* pull bcheck.o from libtcc1.a */
    sym_index = set_elf_sym(symtab_section, 0, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                SHN_UNDEF, "__bound_init");
    if (s1->output_type != TCC_OUTPUT_MEMORY) {
        /* add 'call __bound_init()' in .init section */
        Section *init_section = find_section(s1, ".init");
        unsigned char *pinit = section_ptr_add(init_section, 5);
        pinit[0] = 0xe8;
        write32le(pinit + 1, -4);
        put_elf_reloc(symtab_section, init_section,
            init_section->data_offset - 4, R_386_PC32, sym_index);
            /* R_386_PC32 = R_X86_64_PC32 = 2 */
    }
#endif
}

/* add tcc runtime libraries */
ST_FUNC void tcc_add_runtime(TCCState *s1)
{
    tcc_add_bcheck(s1);
    tcc_add_pragma_libs(s1);
    /* add libc */
    if (!s1->nostdlib) {
        tcc_add_library_err(s1, "c");
#ifdef CONFIG_USE_LIBGCC
        if (!s1->static_link) {
            tcc_add_file(s1, TCC_LIBGCC);
        }
#endif
        tcc_add_support(s1, "libtcc1.a");
        /* add crt end if not memory output */
        if (s1->output_type != TCC_OUTPUT_MEMORY)
            tcc_add_crt(s1, "crtn.o");
    }
}

/* add various standard linker symbols (must be done after the
   sections are filled (for example after allocating common
   symbols)) */
ST_FUNC void tcc_add_linker_symbols(TCCState *s1)
{
    char buf[1024];
    int i;
    Section *s;

    set_elf_sym(symtab_section,
                text_section->data_offset, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                text_section->sh_num, "_etext");
    set_elf_sym(symtab_section,
                data_section->data_offset, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                data_section->sh_num, "_edata");
    set_elf_sym(symtab_section,
                bss_section->data_offset, 0,
                ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                bss_section->sh_num, "_end");
#ifndef TCC_TARGET_PE
    /* horrible new standard ldscript defines */
    add_init_array_defines(s1, ".preinit_array");
    add_init_array_defines(s1, ".init_array");
    add_init_array_defines(s1, ".fini_array");
#endif

    /* add start and stop symbols for sections whose name can be
       expressed in C */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type == SHT_PROGBITS &&
            (s->sh_flags & SHF_ALLOC)) {
            const char *p;
            int ch;

            /* check if section name can be expressed in C */
            p = s->name;
            for(;;) {
                ch = *p;
                if (!ch)
                    break;
                if (!isid(ch) && !isnum(ch))
                    goto next_sec;
                p++;
            }
            snprintf(buf, sizeof(buf), "__start_%s", s->name);
            set_elf_sym(symtab_section,
                        0, 0,
                        ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                        s->sh_num, buf);
            snprintf(buf, sizeof(buf), "__stop_%s", s->name);
            set_elf_sym(symtab_section,
                        s->data_offset, 0,
                        ELFW(ST_INFO)(STB_GLOBAL, STT_NOTYPE), 0,
                        s->sh_num, buf);
        }
    next_sec: ;
    }
}

static void tcc_output_binary(TCCState *s1, FILE *f,
                              const int *sec_order)
{
    Section *s;
    int i, offset, size;

    offset = 0;
    for(i=1;i<s1->nb_sections;i++) {
        s = s1->sections[sec_order[i]];
        if (s->sh_type != SHT_NOBITS &&
            (s->sh_flags & SHF_ALLOC)) {
            while (offset < s->sh_offset) {
                fputc(0, f);
                offset++;
            }
            size = s->sh_size;
            fwrite(s->data, 1, size, f);
            offset += size;
        }
    }
}

#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#define HAVE_PHDR       1
#define EXTRA_RELITEMS  14

/* move the relocation value from .dynsym to .got */
static void patch_dynsym_undef(TCCState *s1, Section *s)
{
    uint32_t *gotd = (void *)s1->got->data;
    ElfW(Sym) *sym;

    gotd += 3; /* dummy entries in .got */
    /* relocate symbols in .dynsym */
    for_each_elem(s, 1, sym, ElfW(Sym)) {
        if (sym->st_shndx == SHN_UNDEF) {
            *gotd++ = sym->st_value + 6; /* XXX 6 is magic ? */
            sym->st_value = 0;
        }
    }
}
#else
#define HAVE_PHDR      1
#define EXTRA_RELITEMS 9

/* zero plt offsets of weak symbols in .dynsym */
static void patch_dynsym_undef(TCCState *s1, Section *s)
{
    ElfW(Sym) *sym;

    for_each_elem(s, 1, sym, ElfW(Sym))
        if (sym->st_shndx == SHN_UNDEF && ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
            sym->st_value = 0;
}
#endif

ST_FUNC void fill_got_entry(TCCState *s1, ElfW_Rel *rel)
{
    int sym_index = ELFW(R_SYM) (rel->r_info);
    ElfW(Sym) *sym = &((ElfW(Sym) *) symtab_section->data)[sym_index];
    unsigned long offset;

    if (sym_index >= s1->nb_sym_attrs)
        return;
    offset = s1->sym_attrs[sym_index].got_offset;
    section_reserve(s1->got, offset + PTR_SIZE);
#ifdef TCC_TARGET_X86_64
    /* only works for x86-64 */
    write32le(s1->got->data + offset + 4, sym->st_value >> 32);
#endif
    write32le(s1->got->data + offset, sym->st_value & 0xffffffff);
}

/* Perform relocation to GOT or PLT entries */
ST_FUNC void fill_got(TCCState *s1)
{
    Section *s;
    ElfW_Rel *rel;
    int i;

    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type != SHT_RELX)
            continue;
        /* no need to handle got relocations */
        if (s->link != symtab_section)
            continue;
        for_each_elem(s, 0, rel, ElfW_Rel) {
            switch (ELFW(R_TYPE) (rel->r_info)) {
                case R_X86_64_GOT32:
                case R_X86_64_GOTPCREL:
		case R_X86_64_GOTPCRELX:
		case R_X86_64_REX_GOTPCRELX:
                case R_X86_64_PLT32:
                    fill_got_entry(s1, rel);
                    break;
            }
        }
    }
}

/* Bind symbols of executable: resolve undefined symbols from exported symbols
   in shared libraries and export non local defined symbols to shared libraries
   if -rdynamic switch was given on command line */
static void bind_exe_dynsyms(TCCState *s1)
{
    const char *name;
    int sym_index, index;
    ElfW(Sym) *sym, *esym;
    int type;

    /* Resolve undefined symbols from dynamic symbols. When there is a match:
       - if STT_FUNC or STT_GNU_IFUNC symbol -> add it in PLT
       - if STT_OBJECT symbol -> add it in .bss section with suitable reloc */
    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        if (sym->st_shndx == SHN_UNDEF) {
            name = (char *) symtab_section->link->data + sym->st_name;
            sym_index = find_elf_sym(s1->dynsymtab_section, name);
            if (sym_index) {
                esym = &((ElfW(Sym) *)s1->dynsymtab_section->data)[sym_index];
                type = ELFW(ST_TYPE)(esym->st_info);
                if ((type == STT_FUNC) || (type == STT_GNU_IFUNC)) {
                    /* Indirect functions shall have STT_FUNC type in executable
                     * dynsym section. Indeed, a dlsym call following a lazy
                     * resolution would pick the symbol value from the
                     * executable dynsym entry which would contain the address
                     * of the function wanted by the caller of dlsym instead of
                     * the address of the function that would return that
                     * address */
                    put_elf_sym(s1->dynsym, 0, esym->st_size,
                                ELFW(ST_INFO)(STB_GLOBAL,STT_FUNC), 0, 0,
                                name);
                } else if (type == STT_OBJECT) {
                    unsigned long offset;
                    ElfW(Sym) *dynsym;
                    offset = bss_section->data_offset;
                    /* XXX: which alignment ? */
                    offset = (offset + 16 - 1) & -16;
                    set_elf_sym (s1->symtab, offset, esym->st_size,
                                 esym->st_info, 0, bss_section->sh_num, name);
                    index = put_elf_sym(s1->dynsym, offset, esym->st_size,
                                        esym->st_info, 0, bss_section->sh_num,
                                        name);
                    /* Ensure R_COPY works for weak symbol aliases */
                    if (ELFW(ST_BIND)(esym->st_info) == STB_WEAK) {
                        for_each_elem(s1->dynsymtab_section, 1, dynsym, ElfW(Sym)) {
                            if ((dynsym->st_value == esym->st_value)
                                && (ELFW(ST_BIND)(dynsym->st_info) == STB_GLOBAL)) {
                                char *dynname = (char *) s1->dynsymtab_section->link->data
                                                + dynsym->st_name;
                                put_elf_sym(s1->dynsym, offset, dynsym->st_size,
                                            dynsym->st_info, 0,
                                            bss_section->sh_num, dynname);
                                break;
                            }
                        }
                    }
                    put_elf_reloc(s1->dynsym, bss_section,
                                  offset, R_COPY, index);
                    offset += esym->st_size;
                    bss_section->data_offset = offset;
                }
            } else {
                /* STB_WEAK undefined symbols are accepted */
                /* XXX: _fp_hw seems to be part of the ABI, so we ignore it */
                if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK ||
                    !strcmp(name, "_fp_hw")) {
                } else {
                    tcc_error_noabort("undefined symbol '%s'", name);
                }
            }
        } else if (s1->rdynamic && ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
            /* if -rdynamic option, then export all non local symbols */
            name = (char *) symtab_section->link->data + sym->st_name;
            set_elf_sym(s1->dynsym, sym->st_value, sym->st_size, sym->st_info,
                        0, sym->st_shndx, name);
        }
    }
}

/* Bind symbols of libraries: export all non local symbols of executable that
   are referenced by shared libraries. The reason is that the dynamic loader
   search symbol first in executable and then in libraries. Therefore a
   reference to a symbol already defined by a library can still be resolved by
   a symbol in the executable. */
static void bind_libs_dynsyms(TCCState *s1)
{
    const char *name;
    int sym_index;
    ElfW(Sym) *sym, *esym;

    for_each_elem(s1->dynsymtab_section, 1, esym, ElfW(Sym)) {
        name = (char *) s1->dynsymtab_section->link->data + esym->st_name;
        sym_index = find_elf_sym(symtab_section, name);
        /* XXX: avoid adding a symbol if already present because of
                -rdynamic ? */
        sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
        if (sym_index && sym->st_shndx != SHN_UNDEF)
            set_elf_sym(s1->dynsym, sym->st_value, sym->st_size, sym->st_info,
                        0, sym->st_shndx, name);
        else if (esym->st_shndx == SHN_UNDEF) {
            /* weak symbols can stay undefined */
            if (ELFW(ST_BIND)(esym->st_info) != STB_WEAK)
                tcc_warning("undefined dynamic symbol '%s'", name);
        }
    }
}

/* Export all non local symbols. This is used by shared libraries so that the
   non local symbols they define can resolve a reference in another shared
   library or in the executable. Correspondingly, it allows undefined local
   symbols to be resolved by other shared libraries or by the executable. */
static void export_global_syms(TCCState *s1)
{
    int nb_syms, dynindex, index;
    const char *name;
    ElfW(Sym) *sym;

    nb_syms = symtab_section->data_offset / sizeof(ElfW(Sym));
    s1->symtab_to_dynsym = tcc_mallocz(sizeof(int) * nb_syms);
    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
	    name = (char *) symtab_section->link->data + sym->st_name;
	    dynindex = put_elf_sym(s1->dynsym, sym->st_value, sym->st_size,
				   sym->st_info, 0, sym->st_shndx, name);
	    index = sym - (ElfW(Sym) *) symtab_section->data;
	    s1->symtab_to_dynsym[index] = dynindex;
        }
    }
}

/* relocate the PLT: compute addresses and offsets in the PLT now that final
   address for PLT and GOT are known (see fill_program_header) */
ST_FUNC void relocate_plt(TCCState *s1)
{
    uint8_t *p, *p_end;

    if (!s1->plt)
      return;

    p = s1->plt->data;
    p_end = p + s1->plt->data_offset;
    if (p < p_end) {
#if defined(TCC_TARGET_I386)
        add32le(p + 2, s1->got->sh_addr);
        add32le(p + 8, s1->got->sh_addr);
        p += 16;
        while (p < p_end) {
            add32le(p + 2, s1->got->sh_addr);
            p += 16;
        }
#elif defined(TCC_TARGET_X86_64)
        int x = s1->got->sh_addr - s1->plt->sh_addr - 6;
        add32le(p + 2, x);
        add32le(p + 8, x - 6);
        p += 16;
        while (p < p_end) {
            add32le(p + 2, x + s1->plt->data - p);
            p += 16;
        }
#elif defined(TCC_TARGET_ARM)
        int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
        write32le(s1->plt->data + 16, x - 16);
        p += 20;
        while (p < p_end) {
            if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
                p += 4;
            add32le(p + 12, x + s1->plt->data - p);
            p += 16;
        }
#elif defined(TCC_TARGET_ARM64)
        uint64_t plt = s1->plt->sh_addr;
        uint64_t got = s1->got->sh_addr;
        uint64_t off = (got >> 12) - (plt >> 12);
        if ((off + ((uint32_t)1 << 20)) >> 21)
            tcc_error("Failed relocating PLT (off=0x%lx, got=0x%lx, plt=0x%lx)", off, got, plt);
        write32le(p, 0xa9bf7bf0); // stp x16,x30,[sp,#-16]!
        write32le(p + 4, (0x90000010 | // adrp x16,...
			  (off & 0x1ffffc) << 3 | (off & 3) << 29));
        write32le(p + 8, (0xf9400211 | // ldr x17,[x16,#...]
			  (got & 0xff8) << 7));
        write32le(p + 12, (0x91000210 | // add x16,x16,#...
			   (got & 0xfff) << 10));
        write32le(p + 16, 0xd61f0220); // br x17
        write32le(p + 20, 0xd503201f); // nop
        write32le(p + 24, 0xd503201f); // nop
        write32le(p + 28, 0xd503201f); // nop
        p += 32;
        while (p < p_end) {
            uint64_t pc = plt + (p - s1->plt->data);
            uint64_t addr = got + read64le(p);
            uint64_t off = (addr >> 12) - (pc >> 12);
            if ((off + ((uint32_t)1 << 20)) >> 21)
                tcc_error("Failed relocating PLT (off=0x%lx, addr=0x%lx, pc=0x%lx)", off, addr, pc);
            write32le(p, (0x90000010 | // adrp x16,...
			  (off & 0x1ffffc) << 3 | (off & 3) << 29));
            write32le(p + 4, (0xf9400211 | // ldr x17,[x16,#...]
			      (addr & 0xff8) << 7));
            write32le(p + 8, (0x91000210 | // add x16,x16,#...
			      (addr & 0xfff) << 10));
            write32le(p + 12, 0xd61f0220); // br x17
            p += 16;
        }
#elif defined(TCC_TARGET_C67)
        /* XXX: TODO */
#else
#error unsupported CPU
#endif
    }
}

/* Allocate strings for section names and decide if an unallocated section
   should be output.

   NOTE: the strsec section comes last, so its size is also correct ! */
static void alloc_sec_names(TCCState *s1, int file_type, Section *strsec)
{
    int i;
    Section *s;

    /* Allocate strings for section names */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        s->sh_name = put_elf_str(strsec, s->name);
        /* when generating a DLL, we include relocations but we may
           patch them */
        if (file_type == TCC_OUTPUT_DLL &&
            s->sh_type == SHT_RELX &&
            !(s->sh_flags & SHF_ALLOC)) {
            /* gr: avoid bogus relocs for empty (debug) sections */
            if (s1->sections[s->sh_info]->sh_flags & SHF_ALLOC)
                prepare_dynamic_rel(s1, s);
            else if (s1->do_debug)
                s->sh_size = s->data_offset;
        } else if (s1->do_debug ||
            file_type == TCC_OUTPUT_OBJ ||
            (s->sh_flags & SHF_ALLOC) ||
            i == (s1->nb_sections - 1)) {
            /* we output all sections if debug or object file */
            s->sh_size = s->data_offset;
        }
    }
}

/* Info to be copied in dynamic section */
struct dyn_inf {
    Section *dynamic;
    Section *dynstr;
    unsigned long dyn_rel_off;
    addr_t rel_addr;
    addr_t rel_size;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
    addr_t bss_addr;
    addr_t bss_size;
#endif
};

/* Assign sections to segments and decide how are sections laid out when loaded
   in memory. This function also fills corresponding program headers. */
static int layout_sections(TCCState *s1, ElfW(Phdr) *phdr, int phnum,
                           Section *interp, Section* strsec,
                           struct dyn_inf *dyninf, int *sec_order)
{
    int i, j, k, file_type, sh_order_index, file_offset;
    unsigned long s_align;
    long long tmp;
    addr_t addr;
    ElfW(Phdr) *ph;
    Section *s;

    file_type = s1->output_type;
    sh_order_index = 1;
    file_offset = 0;
    if (s1->output_format == TCC_OUTPUT_FORMAT_ELF)
        file_offset = sizeof(ElfW(Ehdr)) + phnum * sizeof(ElfW(Phdr));
    s_align = ELF_PAGE_SIZE;
    if (s1->section_align)
        s_align = s1->section_align;

    if (phnum > 0) {
        if (s1->has_text_addr) {
            int a_offset, p_offset;
            addr = s1->text_addr;
            /* we ensure that (addr % ELF_PAGE_SIZE) == file_offset %
               ELF_PAGE_SIZE */
            a_offset = (int) (addr & (s_align - 1));
            p_offset = file_offset & (s_align - 1);
            if (a_offset < p_offset)
                a_offset += s_align;
            file_offset += (a_offset - p_offset);
        } else {
            if (file_type == TCC_OUTPUT_DLL)
                addr = 0;
            else
                addr = ELF_START_ADDR;
            /* compute address after headers */
            addr += (file_offset & (s_align - 1));
        }

        ph = &phdr[0];
        /* Leave one program headers for the program interpreter and one for
           the program header table itself if needed. These are done later as
           they require section layout to be done first. */
        if (interp)
            ph += 1 + HAVE_PHDR;

        /* dynamic relocation table information, for .dynamic section */
        dyninf->rel_addr = dyninf->rel_size = 0;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
        dyninf->bss_addr = dyninf->bss_size = 0;
#endif

        for(j = 0; j < 2; j++) {
            ph->p_type = PT_LOAD;
            if (j == 0)
                ph->p_flags = PF_R | PF_X;
            else
                ph->p_flags = PF_R | PF_W;
            ph->p_align = s_align;

            /* Decide the layout of sections loaded in memory. This must
               be done before program headers are filled since they contain
               info about the layout. We do the following ordering: interp,
               symbol tables, relocations, progbits, nobits */
            /* XXX: do faster and simpler sorting */
            for(k = 0; k < 5; k++) {
                for(i = 1; i < s1->nb_sections; i++) {
                    s = s1->sections[i];
                    /* compute if section should be included */
                    if (j == 0) {
                        if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) !=
                            SHF_ALLOC)
                            continue;
                    } else {
                        if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) !=
                            (SHF_ALLOC | SHF_WRITE))
                            continue;
                    }
                    if (s == interp) {
                        if (k != 0)
                            continue;
                    } else if (s->sh_type == SHT_DYNSYM ||
                               s->sh_type == SHT_STRTAB ||
                               s->sh_type == SHT_HASH) {
                        if (k != 1)
                            continue;
                    } else if (s->sh_type == SHT_RELX) {
                        if (k != 2)
                            continue;
                    } else if (s->sh_type == SHT_NOBITS) {
                        if (k != 4)
                            continue;
                    } else {
                        if (k != 3)
                            continue;
                    }
                    sec_order[sh_order_index++] = i;

                    /* section matches: we align it and add its size */
                    tmp = addr;
                    addr = (addr + s->sh_addralign - 1) &
                        ~(s->sh_addralign - 1);
                    file_offset += (int) ( addr - tmp );
                    s->sh_offset = file_offset;
                    s->sh_addr = addr;

                    /* update program header infos */
                    if (ph->p_offset == 0) {
                        ph->p_offset = file_offset;
                        ph->p_vaddr = addr;
                        ph->p_paddr = ph->p_vaddr;
                    }
                    /* update dynamic relocation infos */
                    if (s->sh_type == SHT_RELX) {
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
                        if (!strcmp(strsec->data + s->sh_name, ".rel.got")) {
                            dyninf->rel_addr = addr;
                            dyninf->rel_size += s->sh_size; /* XXX only first rel. */
                        }
                        if (!strcmp(strsec->data + s->sh_name, ".rel.bss")) {
                            dyninf->bss_addr = addr;
                            dyninf->bss_size = s->sh_size; /* XXX only first rel. */
                        }
#else
                        if (dyninf->rel_size == 0)
                            dyninf->rel_addr = addr;
                        dyninf->rel_size += s->sh_size;
#endif
                    }
                    addr += s->sh_size;
                    if (s->sh_type != SHT_NOBITS)
                        file_offset += s->sh_size;
                }
            }
	    if (j == 0) {
		/* Make the first PT_LOAD segment include the program
		   headers itself (and the ELF header as well), it'll
		   come out with same memory use but will make various
		   tools like binutils strip work better.  */
		ph->p_offset &= ~(ph->p_align - 1);
		ph->p_vaddr &= ~(ph->p_align - 1);
		ph->p_paddr &= ~(ph->p_align - 1);
	    }
            ph->p_filesz = file_offset - ph->p_offset;
            ph->p_memsz = addr - ph->p_vaddr;
            ph++;
            if (j == 0) {
                if (s1->output_format == TCC_OUTPUT_FORMAT_ELF) {
                    /* if in the middle of a page, we duplicate the page in
                       memory so that one copy is RX and the other is RW */
                    if ((addr & (s_align - 1)) != 0)
                        addr += s_align;
                } else {
                    addr = (addr + s_align - 1) & ~(s_align - 1);
                    file_offset = (file_offset + s_align - 1) & ~(s_align - 1);
                }
            }
        }
    }

    /* all other sections come after */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (phnum > 0 && (s->sh_flags & SHF_ALLOC))
            continue;
        sec_order[sh_order_index++] = i;

        file_offset = (file_offset + s->sh_addralign - 1) &
            ~(s->sh_addralign - 1);
        s->sh_offset = file_offset;
        if (s->sh_type != SHT_NOBITS)
            file_offset += s->sh_size;
    }

    return file_offset;
}

static void fill_unloadable_phdr(ElfW(Phdr) *phdr, int phnum, Section *interp,
                                 Section *dynamic)
{
    ElfW(Phdr) *ph;

    /* if interpreter, then add corresponding program header */
    if (interp) {
        ph = &phdr[0];

        if (HAVE_PHDR)
        {
            int len = phnum * sizeof(ElfW(Phdr));

            ph->p_type = PT_PHDR;
            ph->p_offset = sizeof(ElfW(Ehdr));
            ph->p_vaddr = interp->sh_addr - len;
            ph->p_paddr = ph->p_vaddr;
            ph->p_filesz = ph->p_memsz = len;
            ph->p_flags = PF_R | PF_X;
            ph->p_align = 4; /* interp->sh_addralign; */
            ph++;
        }

        ph->p_type = PT_INTERP;
        ph->p_offset = interp->sh_offset;
        ph->p_vaddr = interp->sh_addr;
        ph->p_paddr = ph->p_vaddr;
        ph->p_filesz = interp->sh_size;
        ph->p_memsz = interp->sh_size;
        ph->p_flags = PF_R;
        ph->p_align = interp->sh_addralign;
    }

    /* if dynamic section, then add corresponding program header */
    if (dynamic) {
        ph = &phdr[phnum - 1];

        ph->p_type = PT_DYNAMIC;
        ph->p_offset = dynamic->sh_offset;
        ph->p_vaddr = dynamic->sh_addr;
        ph->p_paddr = ph->p_vaddr;
        ph->p_filesz = dynamic->sh_size;
        ph->p_memsz = dynamic->sh_size;
        ph->p_flags = PF_R | PF_W;
        ph->p_align = dynamic->sh_addralign;
    }
}

/* Fill the dynamic section with tags describing the address and size of
   sections */
static void fill_dynamic(TCCState *s1, struct dyn_inf *dyninf)
{
    Section *dynamic;

    dynamic = dyninf->dynamic;

    /* put dynamic section entries */
    dynamic->data_offset = dyninf->dyn_rel_off;
    put_dt(dynamic, DT_HASH, s1->dynsym->hash->sh_addr);
    put_dt(dynamic, DT_STRTAB, dyninf->dynstr->sh_addr);
    put_dt(dynamic, DT_SYMTAB, s1->dynsym->sh_addr);
    put_dt(dynamic, DT_STRSZ, dyninf->dynstr->data_offset);
    put_dt(dynamic, DT_SYMENT, sizeof(ElfW(Sym)));
#if defined(TCC_TARGET_ARM64) || defined(TCC_TARGET_X86_64)
    put_dt(dynamic, DT_RELA, dyninf->rel_addr);
    put_dt(dynamic, DT_RELASZ, dyninf->rel_size);
    put_dt(dynamic, DT_RELAENT, sizeof(ElfW_Rel));
#else
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
    put_dt(dynamic, DT_PLTGOT, s1->got->sh_addr);
    put_dt(dynamic, DT_PLTRELSZ, dyninf->rel_size);
    put_dt(dynamic, DT_JMPREL, dyninf->rel_addr);
    put_dt(dynamic, DT_PLTREL, DT_REL);
    put_dt(dynamic, DT_REL, dyninf->bss_addr);
    put_dt(dynamic, DT_RELSZ, dyninf->bss_size);
#else
    put_dt(dynamic, DT_REL, dyninf->rel_addr);
    put_dt(dynamic, DT_RELSZ, dyninf->rel_size);
    put_dt(dynamic, DT_RELENT, sizeof(ElfW_Rel));
#endif
#endif
    if (s1->do_debug)
        put_dt(dynamic, DT_DEBUG, 0);
    put_dt(dynamic, DT_NULL, 0);
}

/* Relocate remaining sections and symbols (that is those not related to
   dynamic linking) */
static int final_sections_reloc(TCCState *s1)
{
    int i;
    Section *s;

    relocate_syms(s1, 0);

    if (s1->nb_errors != 0)
        return -1;

    /* relocate sections */
    /* XXX: ignore sections with allocated relocations ? */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
#ifdef TCC_TARGET_I386
        if (s->reloc && s != s1->got && (s->sh_flags & SHF_ALLOC)) //gr
        /* On X86 gdb 7.3 works in any case but gdb 6.6 will crash if SHF_ALLOC
        checking is removed */
#else
        if (s->reloc && s != s1->got)
        /* On X86_64 gdb 7.3 will crash if SHF_ALLOC checking is present */
#endif
            relocate_section(s1, s);
    }

    /* relocate relocation entries if the relocation tables are
       allocated in the executable */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if ((s->sh_flags & SHF_ALLOC) &&
            s->sh_type == SHT_RELX) {
            relocate_rel(s1, s);
        }
    }
    return 0;
}

/* Create an ELF file on disk.
   This function handle ELF specific layout requirements */
static void tcc_output_elf(TCCState *s1, FILE *f, int phnum, ElfW(Phdr) *phdr,
                           int file_offset, int *sec_order)
{
    int i, shnum, offset, size, file_type;
    Section *s;
    ElfW(Ehdr) ehdr;
    ElfW(Shdr) shdr, *sh;

    file_type = s1->output_type;
    shnum = s1->nb_sections;

    memset(&ehdr, 0, sizeof(ehdr));

    if (phnum > 0) {
        ehdr.e_phentsize = sizeof(ElfW(Phdr));
        ehdr.e_phnum = phnum;
        ehdr.e_phoff = sizeof(ElfW(Ehdr));
    }

    /* align to 4 */
    file_offset = (file_offset + 3) & -4;

    /* fill header */
    ehdr.e_ident[0] = ELFMAG0;
    ehdr.e_ident[1] = ELFMAG1;
    ehdr.e_ident[2] = ELFMAG2;
    ehdr.e_ident[3] = ELFMAG3;
    ehdr.e_ident[4] = ELFCLASSW;
    ehdr.e_ident[5] = ELFDATA2LSB;
    ehdr.e_ident[6] = EV_CURRENT;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
    ehdr.e_ident[EI_OSABI] = ELFOSABI_FREEBSD;
#endif
#ifdef TCC_TARGET_ARM
#ifdef TCC_ARM_EABI
    ehdr.e_ident[EI_OSABI] = 0;
    ehdr.e_flags = EF_ARM_EABI_VER4;
    if (file_type == TCC_OUTPUT_EXE || file_type == TCC_OUTPUT_DLL)
        ehdr.e_flags |= EF_ARM_HASENTRY;
    if (s1->float_abi == ARM_HARD_FLOAT)
        ehdr.e_flags |= EF_ARM_VFP_FLOAT;
    else
        ehdr.e_flags |= EF_ARM_SOFT_FLOAT;
#else
    ehdr.e_ident[EI_OSABI] = ELFOSABI_ARM;
#endif
#endif
    switch(file_type) {
    default:
    case TCC_OUTPUT_EXE:
        ehdr.e_type = ET_EXEC;
        ehdr.e_entry = get_elf_sym_addr(s1, "_start", 1);
        break;
    case TCC_OUTPUT_DLL:
        ehdr.e_type = ET_DYN;
        ehdr.e_entry = text_section->sh_addr; /* XXX: is it correct ? */
        break;
    case TCC_OUTPUT_OBJ:
        ehdr.e_type = ET_REL;
        break;
    }
    ehdr.e_machine = EM_TCC_TARGET;
    ehdr.e_version = EV_CURRENT;
    ehdr.e_shoff = file_offset;
    ehdr.e_ehsize = sizeof(ElfW(Ehdr));
    ehdr.e_shentsize = sizeof(ElfW(Shdr));
    ehdr.e_shnum = shnum;
    ehdr.e_shstrndx = shnum - 1;

    fwrite(&ehdr, 1, sizeof(ElfW(Ehdr)), f);
    fwrite(phdr, 1, phnum * sizeof(ElfW(Phdr)), f);
    offset = sizeof(ElfW(Ehdr)) + phnum * sizeof(ElfW(Phdr));

    sort_syms(s1, symtab_section);
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[sec_order[i]];
        if (s->sh_type != SHT_NOBITS) {
            if (s->sh_type == SHT_DYNSYM)
                patch_dynsym_undef(s1, s);
            while (offset < s->sh_offset) {
                fputc(0, f);
                offset++;
            }
            size = s->sh_size;
            if (size)
                fwrite(s->data, 1, size, f);
            offset += size;
        }
    }

    /* output section headers */
    while (offset < ehdr.e_shoff) {
        fputc(0, f);
        offset++;
    }

    for(i = 0; i < s1->nb_sections; i++) {
        sh = &shdr;
        memset(sh, 0, sizeof(ElfW(Shdr)));
        s = s1->sections[i];
        if (s) {
            sh->sh_name = s->sh_name;
            sh->sh_type = s->sh_type;
            sh->sh_flags = s->sh_flags;
            sh->sh_entsize = s->sh_entsize;
            sh->sh_info = s->sh_info;
            if (s->link)
                sh->sh_link = s->link->sh_num;
            sh->sh_addralign = s->sh_addralign;
            sh->sh_addr = s->sh_addr;
            sh->sh_offset = s->sh_offset;
            sh->sh_size = s->sh_size;
        }
        fwrite(sh, 1, sizeof(ElfW(Shdr)), f);
    }
}

/* Write an elf, coff or "binary" file */
static int tcc_write_elf_file(TCCState *s1, const char *filename, int phnum,
                              ElfW(Phdr) *phdr, int file_offset, int *sec_order)
{
    int fd, mode, file_type;
    FILE *f;

    file_type = s1->output_type;
    if (file_type == TCC_OUTPUT_OBJ)
        mode = 0666;
    else
        mode = 0777;
    unlink(filename);
    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, mode);
    if (fd < 0) {
        tcc_error_noabort("could not write '%s'", filename);
        return -1;
    }
    f = fdopen(fd, "wb");
    if (s1->verbose)
        printf("<- %s\n", filename);

#ifdef TCC_TARGET_COFF
    if (s1->output_format == TCC_OUTPUT_FORMAT_COFF)
        tcc_output_coff(s1, f);
    else
#endif
    if (s1->output_format == TCC_OUTPUT_FORMAT_ELF)
        tcc_output_elf(s1, f, phnum, phdr, file_offset, sec_order);
    else
        tcc_output_binary(s1, f, sec_order);
    fclose(f);

    return 0;
}

/* Output an elf, coff or binary file */
/* XXX: suppress unneeded sections */
static int elf_output_file(TCCState *s1, const char *filename)
{
    int i, ret, phnum, shnum, file_type, file_offset, *sec_order;
    struct dyn_inf dyninf;
    ElfW(Phdr) *phdr;
    ElfW(Sym) *sym;
    Section *strsec, *interp, *dynamic, *dynstr;

    file_type = s1->output_type;
    s1->nb_errors = 0;

    /* if linking, also link in runtime libraries (libc, libgcc, etc.) */
    if (file_type != TCC_OUTPUT_OBJ) {
        tcc_add_runtime(s1);
    }

    phdr = NULL;
    sec_order = NULL;
    interp = dynamic = dynstr = NULL; /* avoid warning */
    dyninf.dyn_rel_off = 0; /* avoid warning */

    if (file_type != TCC_OUTPUT_OBJ) {
        relocate_common_syms();

        tcc_add_linker_symbols(s1);

        if (!s1->static_link) {
            if (file_type == TCC_OUTPUT_EXE) {
                char *ptr;
                /* allow override the dynamic loader */
                const char *elfint = getenv("LD_SO");
                if (elfint == NULL)
                    elfint = DEFAULT_ELFINTERP(s1);
                /* add interpreter section only if executable */
                interp = new_section(s1, ".interp", SHT_PROGBITS, SHF_ALLOC);
                interp->sh_addralign = 1;
                ptr = section_ptr_add(interp, 1 + strlen(elfint));
                strcpy(ptr, elfint);
            }

            /* add dynamic symbol table */
            s1->dynsym = new_symtab(s1, ".dynsym", SHT_DYNSYM, SHF_ALLOC,
                                    ".dynstr",
                                    ".hash", SHF_ALLOC);
            dynstr = s1->dynsym->link;

            /* add dynamic section */
            dynamic = new_section(s1, ".dynamic", SHT_DYNAMIC,
                                  SHF_ALLOC | SHF_WRITE);
            dynamic->link = dynstr;
            dynamic->sh_entsize = sizeof(ElfW(Dyn));

            build_got(s1);

            if (file_type == TCC_OUTPUT_EXE) {
                bind_exe_dynsyms(s1);

                if (s1->nb_errors) {
                    ret = -1;
                    goto the_end;
                }

                bind_libs_dynsyms(s1);
            } else /* shared library case: simply export all global symbols */
                export_global_syms(s1);

            build_got_entries(s1);

            /* add a list of needed dlls */
            for(i = 0; i < s1->nb_loaded_dlls; i++) {
                DLLReference *dllref = s1->loaded_dlls[i];
                if (dllref->level == 0)
                    put_dt(dynamic, DT_NEEDED, put_elf_str(dynstr, dllref->name));
            }

            if (s1->rpath)
                put_dt(dynamic, DT_RPATH, put_elf_str(dynstr, s1->rpath));

            /* XXX: currently, since we do not handle PIC code, we
               must relocate the readonly segments */
            if (file_type == TCC_OUTPUT_DLL) {
                if (s1->soname)
                    put_dt(dynamic, DT_SONAME, put_elf_str(dynstr, s1->soname));
                put_dt(dynamic, DT_TEXTREL, 0);
            }

            if (s1->symbolic)
                put_dt(dynamic, DT_SYMBOLIC, 0);

            /* add necessary space for other entries */
            dyninf.dyn_rel_off = dynamic->data_offset;
            dynamic->data_offset += sizeof(ElfW(Dyn)) * EXTRA_RELITEMS;
        } else {
            /* still need to build got entries in case of static link */
            build_got_entries(s1);
        }
    }

    /* we add a section for symbols */
    strsec = new_section(s1, ".shstrtab", SHT_STRTAB, 0);
    put_elf_str(strsec, "");

    /* compute number of sections */
    shnum = s1->nb_sections;

    /* this array is used to reorder sections in the output file */
    sec_order = tcc_malloc(sizeof(int) * shnum);
    sec_order[0] = 0;

    /* compute number of program headers */
    switch(file_type) {
    default:
    case TCC_OUTPUT_OBJ:
        phnum = 0;
        break;
    case TCC_OUTPUT_EXE:
        if (!s1->static_link)
            phnum = 4 + HAVE_PHDR;
        else
            phnum = 2;
        break;
    case TCC_OUTPUT_DLL:
        phnum = 3;
        break;
    }

    /* Allocate strings for section names */
    alloc_sec_names(s1, file_type, strsec);

    /* allocate program segment headers */
    phdr = tcc_mallocz(phnum * sizeof(ElfW(Phdr)));

    /* compute section to program header mapping */
    file_offset = layout_sections(s1, phdr, phnum, interp, strsec, &dyninf,
                                  sec_order);

    /* Fill remaining program header and finalize relocation related to dynamic
       linking. */
    if (phnum > 0) {
        fill_unloadable_phdr(phdr, phnum, interp, dynamic);
        if (dynamic) {
            dyninf.dynamic = dynamic;
            dyninf.dynstr = dynstr;

            fill_dynamic(s1, &dyninf);

            /* put in GOT the dynamic section address and relocate PLT */
            write32le(s1->got->data, dynamic->sh_addr);
            if (file_type == TCC_OUTPUT_EXE
#if defined(TCC_OUTPUT_DLL_WITH_PLT)
                || file_type == TCC_OUTPUT_DLL
#endif
            )
                relocate_plt(s1);

            /* relocate symbols in .dynsym now that final addresses are known */
            for_each_elem(s1->dynsym, 1, sym, ElfW(Sym)) {
                if (sym->st_shndx == SHN_UNDEF) {
                    /* relocate to PLT if symbol corresponds to a PLT entry,
		       but not if it's a weak symbol */
		    if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
		        sym->st_value = 0;
		    else if (sym->st_value)
                        sym->st_value += s1->plt->sh_addr;
                } else if (sym->st_shndx < SHN_LORESERVE) {
                    /* do symbol relocation */
                    sym->st_value += s1->sections[sym->st_shndx]->sh_addr;
                }
            }
        }
    }

    /* if building executable or DLL, then relocate each section
       except the GOT which is already relocated */
    if (file_type != TCC_OUTPUT_OBJ) {
        ret = final_sections_reloc(s1);
        if (ret)
            goto the_end;
    }

    /* Perform relocation to GOT or PLT entries */
    if (file_type == TCC_OUTPUT_EXE && s1->static_link)
        fill_got(s1);

    /* Create the ELF file with name 'filename' */
    ret = tcc_write_elf_file(s1, filename, phnum, phdr, file_offset, sec_order);
 the_end:
    tcc_free(s1->symtab_to_dynsym);
    tcc_free(sec_order);
    tcc_free(phdr);
    tcc_free(s1->sym_attrs);
    s1->sym_attrs = NULL;
    return ret;
}

LIBTCCAPI int tcc_output_file(TCCState *s, const char *filename)
{
    int ret;
#ifdef TCC_TARGET_PE
    if (s->output_type != TCC_OUTPUT_OBJ) {
        ret = pe_output_file(s, filename);
    } else
#endif
        ret = elf_output_file(s, filename);
    return ret;
}

static void *load_data(int fd, unsigned long file_offset, unsigned long size)
{
    void *data;

    data = tcc_malloc(size);
    lseek(fd, file_offset, SEEK_SET);
    read(fd, data, size);
    return data;
}

typedef struct SectionMergeInfo {
    Section *s;            /* corresponding existing section */
    unsigned long offset;  /* offset of the new section in the existing section */
    uint8_t new_section;       /* true if section 's' was added */
    uint8_t link_once;         /* true if link once section */
} SectionMergeInfo;

ST_FUNC int tcc_object_type(int fd, ElfW(Ehdr) *h)
{
    int size = read(fd, h, sizeof *h);
    if (size == sizeof *h && 0 == memcmp(h, ELFMAG, 4)) {
        if (h->e_type == ET_REL)
            return AFF_BINTYPE_REL;
        if (h->e_type == ET_DYN)
            return AFF_BINTYPE_DYN;
    } else if (size >= 8) {
        if (0 == memcmp(h, ARMAG, 8))
            return AFF_BINTYPE_AR;
#ifdef TCC_TARGET_COFF
        if (((struct filehdr*)h)->f_magic == COFF_C67_MAGIC)
            return AFF_BINTYPE_C67;
#endif
    }
    return 0;
}

/* load an object file and merge it with current files */
/* XXX: handle correctly stab (debug) info */
ST_FUNC int tcc_load_object_file(TCCState *s1,
                                int fd, unsigned long file_offset)
{
    ElfW(Ehdr) ehdr;
    ElfW(Shdr) *shdr, *sh;
    int size, i, j, offset, offseti, nb_syms, sym_index, ret;
    unsigned char *strsec, *strtab;
    int *old_to_new_syms;
    char *sh_name, *name;
    SectionMergeInfo *sm_table, *sm;
    ElfW(Sym) *sym, *symtab;
    ElfW_Rel *rel;
    Section *s;

    int stab_index;
    int stabstr_index;

    stab_index = stabstr_index = 0;

    lseek(fd, file_offset, SEEK_SET);
    if (tcc_object_type(fd, &ehdr) != AFF_BINTYPE_REL)
        goto fail1;
    /* test CPU specific stuff */
    if (ehdr.e_ident[5] != ELFDATA2LSB ||
        ehdr.e_machine != EM_TCC_TARGET) {
    fail1:
        tcc_error_noabort("invalid object file");
        return -1;
    }
    /* read sections */
    shdr = load_data(fd, file_offset + ehdr.e_shoff,
                     sizeof(ElfW(Shdr)) * ehdr.e_shnum);
    sm_table = tcc_mallocz(sizeof(SectionMergeInfo) * ehdr.e_shnum);

    /* load section names */
    sh = &shdr[ehdr.e_shstrndx];
    strsec = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);

    /* load symtab and strtab */
    old_to_new_syms = NULL;
    symtab = NULL;
    strtab = NULL;
    nb_syms = 0;
    for(i = 1; i < ehdr.e_shnum; i++) {
        sh = &shdr[i];
        if (sh->sh_type == SHT_SYMTAB) {
            if (symtab) {
                tcc_error_noabort("object must contain only one symtab");
            fail:
                ret = -1;
                goto the_end;
            }
            nb_syms = sh->sh_size / sizeof(ElfW(Sym));
            symtab = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
            sm_table[i].s = symtab_section;

            /* now load strtab */
            sh = &shdr[sh->sh_link];
            strtab = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
        }
    }

    /* now examine each section and try to merge its content with the
       ones in memory */
    for(i = 1; i < ehdr.e_shnum; i++) {
        /* no need to examine section name strtab */
        if (i == ehdr.e_shstrndx)
            continue;
        sh = &shdr[i];
        sh_name = (char *) strsec + sh->sh_name;
        /* ignore sections types we do not handle */
        if (sh->sh_type != SHT_PROGBITS &&
            sh->sh_type != SHT_RELX &&
#ifdef TCC_ARM_EABI
            sh->sh_type != SHT_ARM_EXIDX &&
#endif
            sh->sh_type != SHT_NOBITS &&
            sh->sh_type != SHT_PREINIT_ARRAY &&
            sh->sh_type != SHT_INIT_ARRAY &&
            sh->sh_type != SHT_FINI_ARRAY &&
            strcmp(sh_name, ".stabstr")
            )
            continue;
        if (sh->sh_addralign < 1)
            sh->sh_addralign = 1;
        /* find corresponding section, if any */
        for(j = 1; j < s1->nb_sections;j++) {
            s = s1->sections[j];
            if (!strcmp(s->name, sh_name)) {
                if (!strncmp(sh_name, ".gnu.linkonce",
                             sizeof(".gnu.linkonce") - 1)) {
                    /* if a 'linkonce' section is already present, we
                       do not add it again. It is a little tricky as
                       symbols can still be defined in
                       it. */
                    sm_table[i].link_once = 1;
                    goto next;
                } else {
                    goto found;
                }
            }
        }
        /* not found: create new section */
        s = new_section(s1, sh_name, sh->sh_type, sh->sh_flags & ~SHF_GROUP);
        /* take as much info as possible from the section. sh_link and
           sh_info will be updated later */
        s->sh_addralign = sh->sh_addralign;
        s->sh_entsize = sh->sh_entsize;
        sm_table[i].new_section = 1;
    found:
        if (sh->sh_type != s->sh_type) {
            tcc_error_noabort("invalid section type");
            goto fail;
        }

        /* align start of section */
        offset = s->data_offset;

        if (0 == strcmp(sh_name, ".stab")) {
            stab_index = i;
            goto no_align;
        }
        if (0 == strcmp(sh_name, ".stabstr")) {
            stabstr_index = i;
            goto no_align;
        }

        size = sh->sh_addralign - 1;
        offset = (offset + size) & ~size;
        if (sh->sh_addralign > s->sh_addralign)
            s->sh_addralign = sh->sh_addralign;
        s->data_offset = offset;
    no_align:
        sm_table[i].offset = offset;
        sm_table[i].s = s;
        /* concatenate sections */
        size = sh->sh_size;
        if (sh->sh_type != SHT_NOBITS) {
            unsigned char *ptr;
            lseek(fd, file_offset + sh->sh_offset, SEEK_SET);
            ptr = section_ptr_add(s, size);
            read(fd, ptr, size);
        } else {
            s->data_offset += size;
        }
    next: ;
    }

    /* gr relocate stab strings */
    if (stab_index && stabstr_index) {
        Stab_Sym *a, *b;
        unsigned o;
        s = sm_table[stab_index].s;
        a = (Stab_Sym *)(s->data + sm_table[stab_index].offset);
        b = (Stab_Sym *)(s->data + s->data_offset);
        o = sm_table[stabstr_index].offset;
        while (a < b)
            a->n_strx += o, a++;
    }

    /* second short pass to update sh_link and sh_info fields of new
       sections */
    for(i = 1; i < ehdr.e_shnum; i++) {
        s = sm_table[i].s;
        if (!s || !sm_table[i].new_section)
            continue;
        sh = &shdr[i];
        if (sh->sh_link > 0)
            s->link = sm_table[sh->sh_link].s;
        if (sh->sh_type == SHT_RELX) {
            s->sh_info = sm_table[sh->sh_info].s->sh_num;
            /* update backward link */
            s1->sections[s->sh_info]->reloc = s;
        }
    }
    sm = sm_table;

    /* resolve symbols */
    old_to_new_syms = tcc_mallocz(nb_syms * sizeof(int));

    sym = symtab + 1;
    for(i = 1; i < nb_syms; i++, sym++) {
        if (sym->st_shndx != SHN_UNDEF &&
            sym->st_shndx < SHN_LORESERVE) {
            sm = &sm_table[sym->st_shndx];
            if (sm->link_once) {
                /* if a symbol is in a link once section, we use the
                   already defined symbol. It is very important to get
                   correct relocations */
                if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
                    name = (char *) strtab + sym->st_name;
                    sym_index = find_elf_sym(symtab_section, name);
                    if (sym_index)
                        old_to_new_syms[i] = sym_index;
                }
                continue;
            }
            /* if no corresponding section added, no need to add symbol */
            if (!sm->s)
                continue;
            /* convert section number */
            sym->st_shndx = sm->s->sh_num;
            /* offset value */
            sym->st_value += sm->offset;
        }
        /* add symbol */
        name = (char *) strtab + sym->st_name;
        sym_index = set_elf_sym(symtab_section, sym->st_value, sym->st_size,
                                sym->st_info, sym->st_other,
                                sym->st_shndx, name);
        old_to_new_syms[i] = sym_index;
    }

    /* third pass to patch relocation entries */
    for(i = 1; i < ehdr.e_shnum; i++) {
        s = sm_table[i].s;
        if (!s)
            continue;
        sh = &shdr[i];
        offset = sm_table[i].offset;
        switch(s->sh_type) {
        case SHT_RELX:
            /* take relocation offset information */
            offseti = sm_table[sh->sh_info].offset;
            for_each_elem(s, (offset / sizeof(*rel)), rel, ElfW_Rel) {
                int type;
                unsigned sym_index;
                /* convert symbol index */
                type = ELFW(R_TYPE)(rel->r_info);
                sym_index = ELFW(R_SYM)(rel->r_info);
                /* NOTE: only one symtab assumed */
                if (sym_index >= nb_syms)
                    goto invalid_reloc;
                sym_index = old_to_new_syms[sym_index];
                /* ignore link_once in rel section. */
                if (!sym_index && !sm->link_once
#ifdef TCC_TARGET_ARM
                    && type != R_ARM_V4BX
#endif
                   ) {
                invalid_reloc:
                    tcc_error_noabort("Invalid relocation entry [%2d] '%s' @ %.8x",
                        i, strsec + sh->sh_name, rel->r_offset);
                    goto fail;
                }
                rel->r_info = ELFW(R_INFO)(sym_index, type);
                /* offset the relocation offset */
                rel->r_offset += offseti;
#ifdef TCC_TARGET_ARM
                /* Jumps and branches from a Thumb code to a PLT entry need
                   special handling since PLT entries are ARM code.
                   Unconditional bl instructions referencing PLT entries are
                   handled by converting these instructions into blx
                   instructions. Other case of instructions referencing a PLT
                   entry require to add a Thumb stub before the PLT entry to
                   switch to ARM mode. We set bit plt_thumb_stub of the
                   attribute of a symbol to indicate such a case. */
                if (type == R_ARM_THM_JUMP24)
                    get_sym_attr(s1, sym_index, 1)->plt_thumb_stub = 1;
#endif
            }
            break;
        default:
            break;
        }
    }

    ret = 0;
 the_end:
    tcc_free(symtab);
    tcc_free(strtab);
    tcc_free(old_to_new_syms);
    tcc_free(sm_table);
    tcc_free(strsec);
    tcc_free(shdr);
    return ret;
}

typedef struct ArchiveHeader {
    char ar_name[16];           /* name of this member */
    char ar_date[12];           /* file mtime */
    char ar_uid[6];             /* owner uid; printed as decimal */
    char ar_gid[6];             /* owner gid; printed as decimal */
    char ar_mode[8];            /* file mode, printed as octal   */
    char ar_size[10];           /* file size, printed as decimal */
    char ar_fmag[2];            /* should contain ARFMAG */
} ArchiveHeader;

static int get_be32(const uint8_t *b)
{
    return b[3] | (b[2] << 8) | (b[1] << 16) | (b[0] << 24);
}

static long get_be64(const uint8_t *b)
{
  long long ret = get_be32(b);
  ret = (ret << 32) | (unsigned)get_be32(b+4);
  return (long)ret;
}

/* load only the objects which resolve undefined symbols */
static int tcc_load_alacarte(TCCState *s1, int fd, int size, int entrysize)
{
    long i, bound, nsyms, sym_index, off, ret;
    uint8_t *data;
    const char *ar_names, *p;
    const uint8_t *ar_index;
    ElfW(Sym) *sym;

    data = tcc_malloc(size);
    if (read(fd, data, size) != size)
        goto fail;
    nsyms = entrysize == 4 ? get_be32(data) : get_be64(data);
    ar_index = data + entrysize;
    ar_names = (char *) ar_index + nsyms * entrysize;

    do {
        bound = 0;
        for(p = ar_names, i = 0; i < nsyms; i++, p += strlen(p)+1) {
            sym_index = find_elf_sym(symtab_section, p);
            if(sym_index) {
                sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
                if(sym->st_shndx == SHN_UNDEF) {
                    off = (entrysize == 4
			   ? get_be32(ar_index + i * 4)
			   : get_be64(ar_index + i * 8))
			  + sizeof(ArchiveHeader);
                    ++bound;
                    if(tcc_load_object_file(s1, fd, off) < 0) {
                    fail:
                        ret = -1;
                        goto the_end;
                    }
                }
            }
        }
    } while(bound);
    ret = 0;
 the_end:
    tcc_free(data);
    return ret;
}

/* load a '.a' file */
ST_FUNC int tcc_load_archive(TCCState *s1, int fd)
{
    ArchiveHeader hdr;
    char ar_size[11];
    char ar_name[17];
    char magic[8];
    int size, len, i;
    unsigned long file_offset;

    /* skip magic which was already checked */
    read(fd, magic, sizeof(magic));

    for(;;) {
        len = read(fd, &hdr, sizeof(hdr));
        if (len == 0)
            break;
        if (len != sizeof(hdr)) {
            tcc_error_noabort("invalid archive");
            return -1;
        }
        memcpy(ar_size, hdr.ar_size, sizeof(hdr.ar_size));
        ar_size[sizeof(hdr.ar_size)] = '\0';
        size = strtol(ar_size, NULL, 0);
        memcpy(ar_name, hdr.ar_name, sizeof(hdr.ar_name));
        for(i = sizeof(hdr.ar_name) - 1; i >= 0; i--) {
            if (ar_name[i] != ' ')
                break;
        }
        ar_name[i + 1] = '\0';
        file_offset = lseek(fd, 0, SEEK_CUR);
        /* align to even */
        size = (size + 1) & ~1;
        if (!strcmp(ar_name, "/")) {
            /* coff symbol table : we handle it */
            if(s1->alacarte_link)
                return tcc_load_alacarte(s1, fd, size, 4);
	} else if (!strcmp(ar_name, "/SYM64/")) {
            if(s1->alacarte_link)
                return tcc_load_alacarte(s1, fd, size, 8);
        } else {
            ElfW(Ehdr) ehdr;
            if (tcc_object_type(fd, &ehdr) == AFF_BINTYPE_REL) {
                if (tcc_load_object_file(s1, fd, file_offset) < 0)
                    return -1;
            }
        }
        lseek(fd, file_offset + size, SEEK_SET);
    }
    return 0;
}

#ifndef TCC_TARGET_PE
/* load a DLL and all referenced DLLs. 'level = 0' means that the DLL
   is referenced by the user (so it should be added as DT_NEEDED in
   the generated ELF file) */
ST_FUNC int tcc_load_dll(TCCState *s1, int fd, const char *filename, int level)
{
    ElfW(Ehdr) ehdr;
    ElfW(Shdr) *shdr, *sh, *sh1;
    int i, j, nb_syms, nb_dts, sym_bind, ret;
    ElfW(Sym) *sym, *dynsym;
    ElfW(Dyn) *dt, *dynamic;
    unsigned char *dynstr;
    const char *name, *soname;
    DLLReference *dllref;

    read(fd, &ehdr, sizeof(ehdr));

    /* test CPU specific stuff */
    if (ehdr.e_ident[5] != ELFDATA2LSB ||
        ehdr.e_machine != EM_TCC_TARGET) {
        tcc_error_noabort("bad architecture");
        return -1;
    }

    /* read sections */
    shdr = load_data(fd, ehdr.e_shoff, sizeof(ElfW(Shdr)) * ehdr.e_shnum);

    /* load dynamic section and dynamic symbols */
    nb_syms = 0;
    nb_dts = 0;
    dynamic = NULL;
    dynsym = NULL; /* avoid warning */
    dynstr = NULL; /* avoid warning */
    for(i = 0, sh = shdr; i < ehdr.e_shnum; i++, sh++) {
        switch(sh->sh_type) {
        case SHT_DYNAMIC:
            nb_dts = sh->sh_size / sizeof(ElfW(Dyn));
            dynamic = load_data(fd, sh->sh_offset, sh->sh_size);
            break;
        case SHT_DYNSYM:
            nb_syms = sh->sh_size / sizeof(ElfW(Sym));
            dynsym = load_data(fd, sh->sh_offset, sh->sh_size);
            sh1 = &shdr[sh->sh_link];
            dynstr = load_data(fd, sh1->sh_offset, sh1->sh_size);
            break;
        default:
            break;
        }
    }

    /* compute the real library name */
    soname = tcc_basename(filename);

    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++) {
        if (dt->d_tag == DT_SONAME) {
            soname = (char *) dynstr + dt->d_un.d_val;
        }
    }

    /* if the dll is already loaded, do not load it */
    for(i = 0; i < s1->nb_loaded_dlls; i++) {
        dllref = s1->loaded_dlls[i];
        if (!strcmp(soname, dllref->name)) {
            /* but update level if needed */
            if (level < dllref->level)
                dllref->level = level;
            ret = 0;
            goto the_end;
        }
    }

    /* add the dll and its level */
    dllref = tcc_mallocz(sizeof(DLLReference) + strlen(soname));
    dllref->level = level;
    strcpy(dllref->name, soname);
    dynarray_add((void ***)&s1->loaded_dlls, &s1->nb_loaded_dlls, dllref);

    /* add dynamic symbols in dynsym_section */
    for(i = 1, sym = dynsym + 1; i < nb_syms; i++, sym++) {
        sym_bind = ELFW(ST_BIND)(sym->st_info);
        if (sym_bind == STB_LOCAL)
            continue;
        name = (char *) dynstr + sym->st_name;
        set_elf_sym(s1->dynsymtab_section, sym->st_value, sym->st_size,
                    sym->st_info, sym->st_other, sym->st_shndx, name);
    }

    /* load all referenced DLLs */
    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++) {
        switch(dt->d_tag) {
        case DT_NEEDED:
            name = (char *) dynstr + dt->d_un.d_val;
            for(j = 0; j < s1->nb_loaded_dlls; j++) {
                dllref = s1->loaded_dlls[j];
                if (!strcmp(name, dllref->name))
                    goto already_loaded;
            }
            if (tcc_add_dll(s1, name, AFF_REFERENCED_DLL) < 0) {
                tcc_error_noabort("referenced dll '%s' not found", name);
                ret = -1;
                goto the_end;
            }
        already_loaded:
            break;
        }
    }
    ret = 0;
 the_end:
    tcc_free(dynstr);
    tcc_free(dynsym);
    tcc_free(dynamic);
    tcc_free(shdr);
    return ret;
}

#define LD_TOK_NAME 256
#define LD_TOK_EOF  (-1)

/* return next ld script token */
static int ld_next(TCCState *s1, char *name, int name_size)
{
    int c;
    char *q;

 redo:
    switch(ch) {
    case ' ':
    case '\t':
    case '\f':
    case '\v':
    case '\r':
    case '\n':
        inp();
        goto redo;
    case '/':
        minp();
        if (ch == '*') {
            file->buf_ptr = parse_comment(file->buf_ptr);
            ch = file->buf_ptr[0];
            goto redo;
        } else {
            q = name;
            *q++ = '/';
            goto parse_name;
        }
        break;
    case '\\':
        ch = handle_eob();
        if (ch != '\\')
            goto redo;
        /* fall through */
    /* case 'a' ... 'z': */
    case 'a':
       case 'b':
       case 'c':
       case 'd':
       case 'e':
       case 'f':
       case 'g':
       case 'h':
       case 'i':
       case 'j':
       case 'k':
       case 'l':
       case 'm':
       case 'n':
       case 'o':
       case 'p':
       case 'q':
       case 'r':
       case 's':
       case 't':
       case 'u':
       case 'v':
       case 'w':
       case 'x':
       case 'y':
       case 'z':
    /* case 'A' ... 'z': */
    case 'A':
       case 'B':
       case 'C':
       case 'D':
       case 'E':
       case 'F':
       case 'G':
       case 'H':
       case 'I':
       case 'J':
       case 'K':
       case 'L':
       case 'M':
       case 'N':
       case 'O':
       case 'P':
       case 'Q':
       case 'R':
       case 'S':
       case 'T':
       case 'U':
       case 'V':
       case 'W':
       case 'X':
       case 'Y':
       case 'Z':
    case '_':
    case '.':
    case '$':
    case '~':
        q = name;
    parse_name:
        for(;;) {
            if (!((ch >= 'a' && ch <= 'z') ||
                  (ch >= 'A' && ch <= 'Z') ||
                  (ch >= '0' && ch <= '9') ||
                  strchr("/.-_+=$:\\,~", ch)))
                break;
            if ((q - name) < name_size - 1) {
                *q++ = ch;
            }
            minp();
        }
        *q = '\0';
        c = LD_TOK_NAME;
        break;
    case CH_EOF:
        c = LD_TOK_EOF;
        break;
    default:
        c = ch;
        inp();
        break;
    }
    return c;
}

static int ld_add_file(TCCState *s1, const char filename[])
{
    int ret;

    ret = tcc_add_file_internal(s1, filename, AFF_TYPE_BIN);
    if (ret)
        ret = tcc_add_dll(s1, filename, 0);
    return ret;
}

static inline int new_undef_syms(void)
{
    int ret = 0;
    ret = new_undef_sym;
    new_undef_sym = 0;
    return ret;
}

static int ld_add_file_list(TCCState *s1, const char *cmd, int as_needed)
{
    char filename[1024], libname[1024];
    int t, group, nblibs = 0, ret = 0;
    char **libs = NULL;

    group = !strcmp(cmd, "GROUP");
    if (!as_needed)
        new_undef_syms();
    t = ld_next(s1, filename, sizeof(filename));
    if (t != '(')
        expect("(");
    t = ld_next(s1, filename, sizeof(filename));
    for(;;) {
        libname[0] = '\0';
        if (t == LD_TOK_EOF) {
            tcc_error_noabort("unexpected end of file");
            ret = -1;
            goto lib_parse_error;
        } else if (t == ')') {
            break;
        } else if (t == '-') {
            t = ld_next(s1, filename, sizeof(filename));
            if ((t != LD_TOK_NAME) || (filename[0] != 'l')) {
                tcc_error_noabort("library name expected");
                ret = -1;
                goto lib_parse_error;
            }
            pstrcpy(libname, sizeof libname, &filename[1]);
            if (s1->static_link) {
                snprintf(filename, sizeof filename, "lib%s.a", libname);
            } else {
                snprintf(filename, sizeof filename, "lib%s.so", libname);
            }
        } else if (t != LD_TOK_NAME) {
            tcc_error_noabort("filename expected");
            ret = -1;
            goto lib_parse_error;
        }
        if (!strcmp(filename, "AS_NEEDED")) {
            ret = ld_add_file_list(s1, cmd, 1);
            if (ret)
                goto lib_parse_error;
        } else {
            /* TODO: Implement AS_NEEDED support. Ignore it for now */
            if (!as_needed) {
                ret = ld_add_file(s1, filename);
                if (ret)
                    goto lib_parse_error;
                if (group) {
                    /* Add the filename *and* the libname to avoid future conversions */
                    dynarray_add((void ***) &libs, &nblibs, tcc_strdup(filename));
                    if (libname[0] != '\0')
                        dynarray_add((void ***) &libs, &nblibs, tcc_strdup(libname));
                }
            }
        }
        t = ld_next(s1, filename, sizeof(filename));
        if (t == ',') {
            t = ld_next(s1, filename, sizeof(filename));
        }
    }
    if (group && !as_needed) {
        while (new_undef_syms()) {
            int i;

            for (i = 0; i < nblibs; i ++)
                ld_add_file(s1, libs[i]);
        }
    }
lib_parse_error:
    dynarray_reset(&libs, &nblibs);
    return ret;
}

/* interpret a subset of GNU ldscripts to handle the dummy libc.so
   files */
ST_FUNC int tcc_load_ldscript(TCCState *s1)
{
    char cmd[64];
    char filename[1024];
    int t, ret;

    ch = handle_eob();
    for(;;) {
        t = ld_next(s1, cmd, sizeof(cmd));
        if (t == LD_TOK_EOF)
            return 0;
        else if (t != LD_TOK_NAME)
            return -1;
        if (!strcmp(cmd, "INPUT") ||
            !strcmp(cmd, "GROUP")) {
            ret = ld_add_file_list(s1, cmd, 0);
            if (ret)
                return ret;
        } else if (!strcmp(cmd, "OUTPUT_FORMAT") ||
                   !strcmp(cmd, "TARGET")) {
            /* ignore some commands */
            t = ld_next(s1, cmd, sizeof(cmd));
            if (t != '(')
                expect("(");
            for(;;) {
                t = ld_next(s1, filename, sizeof(filename));
                if (t == LD_TOK_EOF) {
                    tcc_error_noabort("unexpected end of file");
                    return -1;
                } else if (t == ')') {
                    break;
                }
            }
        } else {
            return -1;
        }
    }
    return 0;
}
#endif /* !TCC_TARGET_PE */