[Mesa-dev] [PATCH] st/mesa: fix computing the lowest address for interleaved attribs

[Marek Olšák]

From: Wiktor Janas <wixorpeek at gmail.com>

Ptr can be very well NULL, so when there are two arrays, with one having
offset 0 (and thus NULL Ptr), and the other having a non-zero offset,
the non-zero value is taken as minimum (because of !low_addr ? start ...).
On 32-bit systems, this somehow works. On 64-bit systems, it leads to crashes.
---
 src/mesa/state_tracker/st_draw.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
index 11ebd06..6530a06 100644
--- a/src/mesa/state_tracker/st_draw.c
+++ b/src/mesa/state_tracker/st_draw.c
@@ -315,10 +315,13 @@ setup_interleaved_attribs(struct gl_context *ctx,
    const GLubyte *low_addr = NULL;
 
    /* Find the lowest address. */
-   for (attr = 0; attr < vpv->num_inputs; attr++) {
-      const GLubyte *start = arrays[vp->index_to_input[attr]]->Ptr;
+   if(vpv->num_inputs) {
+      low_addr = arrays[vp->index_to_input[0]]->Ptr;
 
-      low_addr = !low_addr ? start : MIN2(low_addr, start);
+      for (attr = 1; attr < vpv->num_inputs; attr++) {
+         const GLubyte *start = arrays[vp->index_to_input[attr]]->Ptr;
+         low_addr = MIN2(low_addr, start);
+      }
    }
 
    for (attr = 0; attr < vpv->num_inputs; attr++) {
-- 
1.7.1