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libsysprof-capture: use signed int for backtrace return

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This allows us to more safely subtract 1 from the unw_backtrace() to get
the proper number of frames (and detect it in the collector).
This commit is contained in:
Christian Hergert
2020-02-18 14:03:19 -08:00
parent 9f43bf2813
commit 7490a774ab
3 changed files with 16 additions and 12 deletions
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15
src/libsysprof/preload/sysprof-memory-collector.c
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@ -70,7 +70,7 @@ collector_init_ctor (void)
collector_ready = TRUE;
}
static guint
static gint
backtrace_func (SysprofCaptureAddress *addrs,
guint n_addrs,
gpointer user_data)
@ -82,7 +82,7 @@ backtrace_func (SysprofCaptureAddress *addrs,
* and subtract an offset from addrs to avoid having to
* copy frame pointers around.
*/
return unw_backtrace ((void **)addrs - 1, n_addrs);
return unw_backtrace ((void **)addrs - 1, n_addrs) - 1;
# else
static const gint skip = 1;
void **stack = alloca (n_addrs * sizeof (gpointer));
@ -94,13 +94,14 @@ backtrace_func (SysprofCaptureAddress *addrs,
#elif defined(HAVE_EXECINFO_H)
# if GLIB_SIZEOF_VOID_P == 8
/* See note on unw_backtrace() */
return backtrace ((void **)addrs - 1, n_addrs);
return backtrace ((void **)addrs - 1, n_addrs) - 1;
# else /* GLIB_SIZEOF_VOID_P != 8 */
static const gint skip = 1;
void **stack = alloca (n_addrs * sizeof (gpointer));
guint n = backtrace (stack, n_addrs);
for (guint i = 0; i < n; i++)
addrs[i] = GPOINTER_TO_SIZE (stack[i]);
return n;
gint n = backtrace (stack, n_addrs);
for (guint i = skip; i < n; i++)
addrs[i-skip] = GPOINTER_TO_SIZE (stack[i]);
return MAX (0, n - skip);
# endif /* GLIB_SIZEOF_VOID_P */
#else
return 0;