Re: [Mesa-dev] [PATCH] mesa: Add null pointer checks before dereferencing

[Ian Romanick]

On 06/27/2013 02:31 PM, Kenneth Graunke wrote:

On 06/27/2013 02:20 PM, Anuj Phogat wrote:

Assertions are not sufficient to check for null pointers as they don't
show up in release builds. So, add explicit null pointer checks in the
code.

Signed-off-by: Anuj Phogat <anuj.pho...@gmail.com>
---
  src/mesa/program/prog_execute.c | 10 ++++++++++
  1 file changed, 10 insertions(+)

diff --git a/src/mesa/program/prog_execute.c
b/src/mesa/program/prog_execute.c
index b902006..1bcbf6b 100644
--- a/src/mesa/program/prog_execute.c
+++ b/src/mesa/program/prog_execute.c
@@ -200,6 +200,8 @@ fetch_vector4(const struct prog_src_register *source,
  {
     const GLfloat *src = get_src_register_pointer(source, machine);
     ASSERT(src);
+   if (src == NULL)
+      return;

     if (source->Swizzle == SWIZZLE_NOOP) {
        /* no swizzling */
@@ -303,6 +305,8 @@ fetch_vector1(const struct prog_src_register *source,
  {
     const GLfloat *src = get_src_register_pointer(source, machine);
     ASSERT(src);
+   if (src == NULL)
+      return;

     result[0] = src[GET_SWZ(source->Swizzle, 0)];

@@ -320,6 +324,9 @@ fetch_vector1ui(const struct prog_src_register
*source,
                  const struct gl_program_machine *machine)
  {
     const GLuint *src = (GLuint *) get_src_register_pointer(source,
machine);
+   ASSERT(src);
+   if (src == NULL)
+      return 0;
     return src[GET_SWZ(source->Swizzle, 0)];
  }

@@ -1439,8 +1446,11 @@ _mesa_execute_program(struct gl_context * ctx,
           {
              const struct prog_src_register *source = &inst->SrcReg[0];
              const GLfloat *src = get_src_register_pointer(source,
machine);
+            ASSERT(src);
              GLfloat result[4];
              GLuint i;
+            if (src == NULL)
+               return GL_FALSE;
              for (i = 0; i < 4; i++) {
                 const GLuint swz = GET_SWZ(source->Swizzle, i);
                 if (swz == SWIZZLE_ZERO)

I don't like this.  I would just put an abort() below the _mesa_problem
in get_src_register_pointer.

Or return ZeroVec instead of NULL.

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