mempool: Reduce the assertion into an alignment adjustment for the base

Instead of asserting that the caller passed in a chunk-aligned base
pointer, just perform the fixup whilst initialising the mempool. This
means that the caller (xcb!) cannot assume that the mempool->base is
then the same base pointer as passed in and so needs to store it
separately for use in computing SHM offsets.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/cairo-mempool.c b/src/cairo-mempool.c
index 296b73932..96e4a62b2 100644
--- a/src/cairo-mempool.c
+++ b/src/cairo-mempool.c
@@ -283,9 +283,18 @@ _cairo_mempool_init (cairo_mempool_t *pool,
 		      void *base, size_t bytes,
 		      int min_bits, int num_sizes)
 {
+    unsigned long tmp;
     int num_blocks;
     int i;
 
+    /* Align the start to an integral chunk */
+    tmp = ((unsigned long) base) & ((1 << min_bits) - 1);
+    if (tmp) {
+	tmp = (1 << min_bits) - tmp;
+	base = (char *)base + tmp;
+	bytes -= tmp;
+    }
+
     assert ((((unsigned long) base) & ((1 << min_bits) - 1)) == 0);
     assert (num_sizes < ARRAY_LENGTH (pool->free));