Update (incl. PR#1547).
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pk
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@ -1,4 +1,4 @@
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.\" $NetBSD: link.5,v 1.3 1994/11/30 19:31:21 jtc Exp $
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.\" $NetBSD: link.5,v 1.4 1995/09/30 21:28:19 pk Exp $
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.\"
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.\" Copyright (c) 1993 Paul Kranenburg
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.\" All rights reserved.
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@ -59,16 +59,16 @@ linked program or shared object image as the existing
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.Xr a.out
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format offers no room for it elsewhere.
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.Pp
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Several utilities cooperate to ensure that the task of getting a program
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Several utilities co-operate to ensure that the task of getting a program
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ready to run can complete successfully in a way that optimizes the use
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of system resources. The compiler emits PIC code from which shared libraries
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can be build by
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.Xr ld 1.
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can be built by
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.Xr ld 1 .
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The compiler also includes size information of any initialized data items
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through the .size assembler directive. PIC code differs from conventional code
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in that it accesses data variables through an indirection table, the
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Global Offset Table, by convention accessable by the reserved name
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.Em _GLOBAL_OFFSET_TABLE_.
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.Em _GLOBAL_OFFSET_TABLE_ .
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The exact mechanism used for this is machine dependent, usually a machine
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register is reserved for the purpose. The rational behind this construct
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is to generate code that is independent of the actual load address. Only
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@ -91,7 +91,7 @@ _DYNAMIC is relocated to 0, there is no need to invoke the run-time
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link-editor. If this symbol is non-zero, it points at a data structure from
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which the location of the necessary relocation- and symbol information can
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be derived. This is most notably used by the start-up module,
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.Em crt0.
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.Em crt0 .
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The _DYNAMIC structure is conventionally located at the start of the data
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segment of the image to which it pertains.
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.Pp
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@ -122,14 +122,18 @@ implementation. The current version numbers understood by ld and ld.so are
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.Em LD_VERSION_SUN (3),
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which is used by the SunOS 4.x releases, and
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.Em LD_VERSION_BSD (8),
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which is currently in use by NetBSD release 0.9B.
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which is currently in use by NetBSD.
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.It Fa d_un
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Refers to a
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.Em d_version
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dependent data structure.
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.It Fa so_debug
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.It Fa d_debug
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this field provides debuggers with a hook to access symbol tables of shared
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objects loaded as a result of the actions of the run-time link-editor.
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.It Fa d_entry
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this field is obsoleted by CRT interface version CRT_VERSION_BSD4, and is
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replaced by the crt_ldentry in
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.Fa crt_ldso .
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.El
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.Pp
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The
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@ -142,7 +146,7 @@ and relocation information is located.
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struct section_dispatch_table {
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struct so_map *sdt_loaded;
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long sdt_sods;
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long sdt_filler1;
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long sdt_paths;
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long sdt_got;
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long sdt_plt;
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long sdt_rel;
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@ -157,16 +161,22 @@ struct section_dispatch_table {
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};
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.Ed
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.Pp
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.Bl -tag -width sdt_filler1
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.Bl -tag -width sdt_loaded
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.It Fa sdt_loaded
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A pointer to the first link map loaded (see below). This field is set by
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.Xr ld.so.
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.Xr ld.so
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for the benefit of debuggers that may use it to load a shared object's
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symbol table.
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.It Fa sdt_sods
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The start of a (linked) list of shared object descriptors needed by
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.Em this
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object.
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.It Fa sdt_filler1
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Depricated (used by SunOS to specify library search rules).
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.It Fa sdt_paths
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Library search rules. A colon separated list of directories corresponding
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to the
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.Fl R
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option of
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.Xr ld 1 .
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.It Fa sdt_got
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The location of the Global Offset Table within this image.
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.It Fa sdt_plt
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@ -192,7 +202,7 @@ The number of buckets in
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.Fa sdt_hash
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.It Fa sdt_strings
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The location of the symbol string table that goes with
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.Fa sdt_nzlist.
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.Fa sdt_nzlist .
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.It Fa sdt_str_sz
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The size of the string table.
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.It Fa sdt_text_sz
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@ -238,7 +248,7 @@ see also
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.Xr ldconfig 8
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.Pc
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for a shared object matching
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.Em lib\&<sod_name>\&.so.n.m.
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.Em lib\&<sod_name>\&.so.n.m .
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If not set,
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.Fa sod_name
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should point at a full path name for the desired shared object.
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@ -298,7 +308,7 @@ of shared objects. An array of these lives in the shared object's
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text segment and is addressed by the
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.Fa sdt_nzlist
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field of
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.Fa section_dispatch_table.
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.Fa section_dispatch_table .
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.Bd -literal -offset indent
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struct nzlist {
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struct nlist nlist;
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@ -392,7 +402,7 @@ A dynamically linked binary contains a
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structure which can be located by means of the
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.Fa d_debug
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field in
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.Fa _dynamic.
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.Fa _dynamic .
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.Bd -literal -offset indent
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struct so_debug {
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int dd_version;
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@ -420,7 +430,7 @@ module,
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to be some convenient place before the call to _main.
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.It Fa dd_bpt_shadow
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Contains the original instruction that was at
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.Fa dd_bpt_addr.
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.Fa dd_bpt_addr .
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The debugger is expected to put this instruction back before continuing the
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program.
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.It Fa dd_cc
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@ -431,7 +441,7 @@ may be interested in.
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The
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.Em ld_entry
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structure defines a set of service routines within ld.so. See
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.Xr libdl.a
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.Xr dlfcn 3
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for more information.
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.Bd -literal -offset indent
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struct ld_entry {
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@ -439,12 +449,13 @@ struct ld_entry {
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int (*dlclose)(void *);
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void *(*dlsym)(void *, char *);
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int (*dlctl)(void *, int, void *);
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void (*dlexit) __P((void));
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};
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.Ed
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The
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.Fa crt_ldso
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structure defines the interface between the start-up code in crt0 and ld.so.
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structure defines the interface between ld.so and the start-up code in crt0.
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.Bd -literal -offset indent
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struct crt_ldso {
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int crt_ba;
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@ -455,10 +466,12 @@ struct crt_ldso {
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caddr_t crt_bp;
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char *crt_prog;
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char *crt_ldso;
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char *crt_ldentry;
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};
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#define CRT_VERSION_SUN 1
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#define CRT_VERSION_BSD2 2
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#define CRT_VERSION_BSD3 3
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#define CRT_VERSION_BSD4 4
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.Ed
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.Bl -tag -width crt_dzfd
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.It Fa crt_ba
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@ -484,6 +497,10 @@ See
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The name of the main program as determined by crt0 (CRT_VERSION_BSD3 only).
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.It Fa crt_ldso
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The path of the run-time linker as mapped by crt0 (CRT_VERSION_BSD4 only).
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.It Fa crt_ldentry
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The
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.Xr dlfcn 3
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entry points provided by the run-time linker (CRT_VERSION_BSD4 only).
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.El
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.Pp
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The
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@ -549,7 +566,7 @@ Index of the string representing the full path name of the library.
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The version numbers of the shared library.
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.It Fa hi_ndewey
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The number of valid entries in
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.Fa hi_dewey.
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.Fa hi_dewey .
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.It Fa hi_next
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Next bucket in case of hashing collisions.
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.El
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