[Libunwind-devel] [PATCH 03/35] Workaround non-power-of-two i386 sizeof(long double) in src/mi/mempool.c

[Tommi Rantala]

To ensure that we return properly aligned pointers from sos_alloc(),
MAX_ALIGN must be a power-of-two. On i386 the power-of-two assumption
fails as sizeof(long double) = 12. Fix this by rounding up to 16.
---
 src/mi/mempool.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/mi/mempool.c b/src/mi/mempool.c
index a18bb21..3355265 100644
--- a/src/mi/mempool.c
+++ b/src/mi/mempool.c
@@ -31,7 +31,11 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.  */
 #ifdef __BIGGEST_ALIGNMENT__
 #define MAX_ALIGN      __BIGGEST_ALIGNMENT__
 #else
-#define MAX_ALIGN      (sizeof (long double))
+/* Crude hack to check that MAX_ALIGN is power-of-two.
+ * sizeof(long double) = 12 on i386. */
+#define MAX_ALIGN_(n)  (n < 8 ? 8 : \
+                        n < 16 ? 16 : n)
+#define MAX_ALIGN      MAX_ALIGN_(sizeof (long double))
 #endif
 
 static char sos_memory[SOS_MEMORY_SIZE];
-- 
1.7.9.5