7274f01bb8
QTAILQ is a doubly linked list, with a pointer-to-pointer to the last element from the head, and the previous element from each node. But if you squint enough, QTAILQ becomes a combination of a singly-linked forwards list, and another singly-linked list which goes backwards and is circular. This is the idea that lets QTAILQ implement reverse iteration: only, because the backwards list points inside the node, accessing the previous element needs to go two steps back and one forwards. What this patch does is implement it in these terms, without actually changing the in-memory layout at all. The coexistence of the two lists is realized by making QTAILQ_HEAD and QTAILQ_ENTRY unions of the forwards pointer and a generic QTailQLink node. Thq QTailQLink can walk the list in both directions; the union is needed so that the forwards pointer can have the correct type, as a sort of poor man's template. While there are other ways to get the same layout without a union, this one has the advantage of simpler operation in the debugger, because the fields tqh_first and tqe_next still exist as before the patch. Those fields are also used by scripts/qemugdb/mtree.py, so it's a good idea to preserve them. The advantage of the new representation is that the two-back-one-forward dance done by backwards accesses can be done all while operating on QTailQLinks. No casting to the head struct is needed anymore because, even though the QTailQLink's forward pointer is a void *, we can use typeof to recover the correct type. This patch only changes the implementation, not the interface. The next patch will remove the head struct name from the backwards visit macros. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
115 lines
4.2 KiB
C
115 lines
4.2 KiB
C
/* Macro file for Coccinelle
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*
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* Copyright (C) 2015 Red Hat, Inc.
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*
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* Authors:
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* Paolo Bonzini <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or, at your
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* option, any later version. See the COPYING file in the top-level directory.
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*/
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/* Coccinelle only does limited parsing of headers, and chokes on some idioms
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* defined in compiler.h and queue.h. Macros that Coccinelle must know about
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* in order to parse .c files must be in a separate macro file---which is
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* exactly what you're staring at now.
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*
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* To use this file, add the "--macro-file scripts/cocci-macro-file.h" to the
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* Coccinelle command line.
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*/
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/* From qemu/compiler.h */
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#define QEMU_GNUC_PREREQ(maj, min) 1
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#define QEMU_NORETURN __attribute__ ((__noreturn__))
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#define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
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#define QEMU_SENTINEL __attribute__((sentinel))
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#define QEMU_PACKED __attribute__((gcc_struct, packed))
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#define cat(x,y) x ## y
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#define cat2(x,y) cat(x,y)
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#define QEMU_BUILD_BUG_ON(x) \
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typedef char cat2(qemu_build_bug_on__,__LINE__)[(x)?-1:1] __attribute__((unused));
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#define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
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#define xglue(x, y) x ## y
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#define glue(x, y) xglue(x, y)
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#define stringify(s) tostring(s)
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#define tostring(s) #s
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#define typeof_field(type, field) typeof(((type *)0)->field)
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#define type_check(t1,t2) ((t1*)0 - (t2*)0)
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/* From qemu/queue.h */
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#define QLIST_HEAD(name, type) \
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struct name { \
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struct type *lh_first; /* first element */ \
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}
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#define QLIST_HEAD_INITIALIZER(head) \
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{ NULL }
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#define QLIST_ENTRY(type) \
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struct { \
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struct type *le_next; /* next element */ \
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struct type **le_prev; /* address of previous next element */ \
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}
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/*
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* Singly-linked List definitions.
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*/
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#define QSLIST_HEAD(name, type) \
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struct name { \
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struct type *slh_first; /* first element */ \
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}
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#define QSLIST_HEAD_INITIALIZER(head) \
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{ NULL }
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#define QSLIST_ENTRY(type) \
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struct { \
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struct type *sle_next; /* next element */ \
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}
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/*
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* Simple queue definitions.
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*/
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#define QSIMPLEQ_HEAD(name, type) \
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struct name { \
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struct type *sqh_first; /* first element */ \
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struct type **sqh_last; /* addr of last next element */ \
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}
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#define QSIMPLEQ_HEAD_INITIALIZER(head) \
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{ NULL, &(head).sqh_first }
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#define QSIMPLEQ_ENTRY(type) \
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struct { \
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struct type *sqe_next; /* next element */ \
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}
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/*
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* Tail queue definitions.
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*/
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#define QTAILQ_HEAD(name, type) \
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union name { \
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struct type *tqh_first; /* first element */ \
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QTailQLink tqh_circ; /* link for last element */ \
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}
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#define QTAILQ_HEAD_INITIALIZER(head) \
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{ .tqh_circ = { NULL, &(head).tqh_circ } }
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#define QTAILQ_ENTRY(type) \
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union { \
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struct type *tqe_next; /* next element */ \
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QTailQLink tqe_circ; /* link for prev element */ \
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}
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/* From glib */
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#define g_assert_cmpint(a, op, b) g_assert(a op b)
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#define g_assert_cmpuint(a, op, b) g_assert(a op b)
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#define g_assert_cmphex(a, op, b) g_assert(a op b)
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#define g_assert_cmpstr(a, op, b) g_assert(strcmp(a, b) op 0)
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