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malloc: Avoid optimizer warning with GCC 7 and -O3

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This commit is contained in:
Florian Weimer
2017-08-10 15:58:28 +02:00
parent bd80111ed9
commit eac43cbb8d
2 changed files with 21 additions and 4 deletions
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20
malloc/malloc.c
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@ -1658,6 +1658,9 @@ typedef struct malloc_chunk *mfastbinptr;
#define arena_is_corrupt(A) (((A)->flags & ARENA_CORRUPTION_BIT))
#define set_arena_corrupt(A) ((A)->flags |= ARENA_CORRUPTION_BIT)
/* Maximum size of memory handled in fastbins. */
static INTERNAL_SIZE_T global_max_fast;
/*
Set value of max_fast.
Use impossibly small value if 0.
@ -1668,8 +1671,20 @@ typedef struct malloc_chunk *mfastbinptr;
#define set_max_fast(s) \
global_max_fast = (((s) == 0) \
? SMALLBIN_WIDTH : ((s + SIZE_SZ) & ~MALLOC_ALIGN_MASK))
#define get_max_fast() global_max_fast
static inline INTERNAL_SIZE_T
get_max_fast (void)
{
/* Tell the GCC optimizers that global_max_fast is never larger
than MAX_FAST_SIZE. This avoids out-of-bounds array accesses in
_int_malloc after constant propagation of the size parameter.
(The code never executes because malloc preserves the
global_max_fast invariant, but the optimizers may not recognize
this.) */
if (global_max_fast > MAX_FAST_SIZE)
__builtin_unreachable ();
return global_max_fast;
}
/*
----------- Internal state representation and initialization -----------
@ -1797,9 +1812,6 @@ static struct malloc_par mp_ =
#endif
};
/* Maximum size of memory handled in fastbins. */
static INTERNAL_SIZE_T global_max_fast;
/*
Initialize a malloc_state struct.