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Subvert tail call optimization in backtrace test.

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Re-structure alloc_[01](), which are mutually tail-recursive functions,
to do (unnecessary) work post-recursion so that the compiler cannot
perform tail call optimization, thus preserving intentionally unique
call paths in captured backtraces.
This commit is contained in:
Jason Evans 2014-01-21 14:59:40 -08:00
parent e2206edebc
commit 898960247a
1 changed files with 17 additions and 11 deletions
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24
test/unit/prof_accum.c
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@ -28,18 +28,24 @@ static void *alloc_##n(unsigned bits);
static void * \ static void * \
alloc_##n(unsigned bits) \ alloc_##n(unsigned bits) \
{ \ { \
void *p; \
\ \
if (bits == 0) { \ if (bits == 0) \
void *p = mallocx(1, 0); \ p = mallocx(1, 0); \
assert_ptr_not_null(p, "Unexpected mallocx() failure"); \ else { \
return (p); \
} \
\
switch (bits & 0x1U) { \ switch (bits & 0x1U) { \
case 0: return (alloc_0(bits >> 1)); \ case 0: \
case 1: return (alloc_1(bits >> 1)); \ p = alloc_0(bits >> 1); \
break; \
case 1: \
p = alloc_1(bits >> 1); \
break; \
default: not_reached(); \ default: not_reached(); \
} \ } \
} \
/* Intentionally sabotage tail call optimization. */ \
assert_ptr_not_null(p, "Unexpected mallocx() failure"); \
return (p); \
} }
alloc_n_proto(0) alloc_n_proto(0)
alloc_n_proto(1) alloc_n_proto(1)
@ -74,7 +80,7 @@ thd_start(void *varg)
i+1 == NALLOCS_PER_THREAD) { i+1 == NALLOCS_PER_THREAD) {
bt_count = prof_bt_count(); bt_count = prof_bt_count();
assert_zu_le(bt_count_prev+(i-i_prev), bt_count, assert_zu_le(bt_count_prev+(i-i_prev), bt_count,
"Expected larger bactrace count increase"); "Expected larger backtrace count increase");
i_prev = i; i_prev = i;
bt_count_prev = bt_count; bt_count_prev = bt_count;
} }