From eac43cbb8d808a40004aa0a4a286f5c5155beccb Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Thu, 10 Aug 2017 15:58:28 +0200 Subject: malloc: Avoid optimizer warning with GCC 7 and -O3 --- malloc/malloc.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) (limited to 'malloc') diff --git a/malloc/malloc.c b/malloc/malloc.c index 54e406bcb6..e3ff778113 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -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. -- cgit v1.2.3-70-g09d2