http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56726
Bug #: 56726
Summary: i386: MALLOC_ABI_ALIGNMENT is too small (usually)
Classification: Unclassified
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: c...@pobox.com
Observed malloc alignment for the i386 ABI is double POINTER_SIZE.
BITS_PER_WORD, the current default, is usually too small. (It's right only on
X32.)
Proposed patch:
--- gcc/config/i386/i386.h (revision 197055)
+++ gcc/config/i386/i386.h (working copy)
@@ -815,6 +815,14 @@
x86_field_alignment (FIELD, COMPUTED)
#endif
+/* The maximum alignment 'malloc' honors.
+
+ This value is taken from glibc documentation for memalign(). It may
+ be up to double the very conservative GCC default. This should be safe,
+ since even the GCC 4.8 default of BIGGEST_ALIGNMENT usually worked. */
+
+#define MALLOC_ABI_ALIGNMENT (POINTER_SIZE * 2)
+
/* If defined, a C expression to compute the alignment given to a
constant that is being placed in memory. EXP is the constant
and ALIGN is the alignment that the object would ordinarily have
