272 lines
6.9 KiB
C
272 lines
6.9 KiB
C
/* mmap.c -- Memory allocation with mmap.
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Copyright (C) 2012-2014 Free Software Foundation, Inc.
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Written by Ian Lance Taylor, Google.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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(1) Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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(2) Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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(3) The name of the author may not be used to
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endorse or promote products derived from this software without
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specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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#include "config.h"
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#include <errno.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#include "backtrace.h"
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#include "internal.h"
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/* Memory allocation on systems that provide anonymous mmap. This
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permits the backtrace functions to be invoked from a signal
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handler, assuming that mmap is async-signal safe. */
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#ifndef MAP_ANONYMOUS
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#define MAP_ANONYMOUS MAP_ANON
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#endif
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/* A list of free memory blocks. */
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struct backtrace_freelist_struct
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{
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/* Next on list. */
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struct backtrace_freelist_struct *next;
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/* Size of this block, including this structure. */
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size_t size;
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};
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/* Free memory allocated by backtrace_alloc. */
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static void
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backtrace_free_locked (struct backtrace_state *state, void *addr, size_t size)
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{
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/* Just leak small blocks. We don't have to be perfect. */
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if (size >= sizeof (struct backtrace_freelist_struct))
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{
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struct backtrace_freelist_struct *p;
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p = (struct backtrace_freelist_struct *) addr;
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p->next = state->freelist;
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p->size = size;
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state->freelist = p;
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}
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}
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/* Allocate memory like malloc. */
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void *
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backtrace_alloc (struct backtrace_state *state,
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size_t size, backtrace_error_callback error_callback,
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void *data)
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{
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void *ret;
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int locked;
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struct backtrace_freelist_struct **pp;
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size_t pagesize;
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size_t asksize;
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void *page;
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ret = NULL;
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/* If we can acquire the lock, then see if there is space on the
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free list. If we can't acquire the lock, drop straight into
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using mmap. __sync_lock_test_and_set returns the old state of
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the lock, so we have acquired it if it returns 0. */
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if (!state->threaded)
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locked = 1;
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else
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locked = __sync_lock_test_and_set (&state->lock_alloc, 1) == 0;
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if (locked)
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{
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for (pp = &state->freelist; *pp != NULL; pp = &(*pp)->next)
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{
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if ((*pp)->size >= size)
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{
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struct backtrace_freelist_struct *p;
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p = *pp;
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*pp = p->next;
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/* Round for alignment; we assume that no type we care about
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is more than 8 bytes. */
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size = (size + 7) & ~ (size_t) 7;
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if (size < p->size)
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backtrace_free_locked (state, (char *) p + size,
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p->size - size);
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ret = (void *) p;
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break;
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}
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}
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if (state->threaded)
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__sync_lock_release (&state->lock_alloc);
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}
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if (ret == NULL)
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{
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/* Allocate a new page. */
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pagesize = getpagesize ();
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asksize = (size + pagesize - 1) & ~ (pagesize - 1);
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page = mmap (NULL, asksize, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (page == NULL)
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error_callback (data, "mmap", errno);
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else
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{
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size = (size + 7) & ~ (size_t) 7;
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if (size < asksize)
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backtrace_free (state, (char *) page + size, asksize - size,
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error_callback, data);
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ret = page;
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}
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}
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return ret;
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}
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/* Free memory allocated by backtrace_alloc. */
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void
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backtrace_free (struct backtrace_state *state, void *addr, size_t size,
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backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
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void *data ATTRIBUTE_UNUSED)
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{
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int locked;
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/* If we can acquire the lock, add the new space to the free list.
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If we can't acquire the lock, just leak the memory.
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__sync_lock_test_and_set returns the old state of the lock, so we
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have acquired it if it returns 0. */
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if (!state->threaded)
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locked = 1;
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else
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locked = __sync_lock_test_and_set (&state->lock_alloc, 1) == 0;
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if (locked)
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{
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backtrace_free_locked (state, addr, size);
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if (state->threaded)
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__sync_lock_release (&state->lock_alloc);
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}
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}
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/* Grow VEC by SIZE bytes. */
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void *
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backtrace_vector_grow (struct backtrace_state *state,size_t size,
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backtrace_error_callback error_callback,
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void *data, struct backtrace_vector *vec)
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{
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void *ret;
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if (size > vec->alc)
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{
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size_t pagesize;
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size_t alc;
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void *base;
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pagesize = getpagesize ();
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alc = vec->size + size;
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if (vec->size == 0)
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alc = 16 * size;
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else if (alc < pagesize)
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{
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alc *= 2;
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if (alc > pagesize)
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alc = pagesize;
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}
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else
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alc = (alc + pagesize - 1) & ~ (pagesize - 1);
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base = backtrace_alloc (state, alc, error_callback, data);
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if (base == NULL)
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return NULL;
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if (vec->base != NULL)
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{
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memcpy (base, vec->base, vec->size);
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backtrace_free (state, vec->base, vec->alc, error_callback, data);
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}
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vec->base = base;
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vec->alc = alc - vec->size;
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}
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ret = (char *) vec->base + vec->size;
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vec->size += size;
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vec->alc -= size;
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return ret;
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}
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/* Finish the current allocation on VEC. */
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void *
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backtrace_vector_finish (
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struct backtrace_state *state ATTRIBUTE_UNUSED,
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struct backtrace_vector *vec,
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backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
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void *data ATTRIBUTE_UNUSED)
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{
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void *ret;
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ret = vec->base;
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vec->base = (char *) vec->base + vec->size;
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vec->size = 0;
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return ret;
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}
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/* Release any extra space allocated for VEC. */
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int
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backtrace_vector_release (struct backtrace_state *state,
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struct backtrace_vector *vec,
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backtrace_error_callback error_callback,
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void *data)
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{
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size_t size;
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size_t alc;
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size_t aligned;
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/* Make sure that the block that we free is aligned on an 8-byte
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boundary. */
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size = vec->size;
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alc = vec->alc;
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aligned = (size + 7) & ~ (size_t) 7;
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alc -= aligned - size;
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backtrace_free (state, (char *) vec->base + aligned, alc,
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error_callback, data);
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vec->alc = 0;
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return 1;
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}
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