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authorFlorian Weimer <fweimer@redhat.com>2017-08-10 15:58:28 +0200
committerFlorian Weimer <fweimer@redhat.com>2017-08-10 15:58:28 +0200
commiteac43cbb8d808a40004aa0a4a286f5c5155beccb (patch)
treeb17052f4a48a6fd8da44c12f1fd61b4bce196dcf /malloc
parentbd80111ed9cb93b2d56720dcd1d1f259616c27ae (diff)
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malloc: Avoid optimizer warning with GCC 7 and -O3
Diffstat (limited to 'malloc')
-rw-r--r--malloc/malloc.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 54e406bcb67..e3ff778113f 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.