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

[Brian Paul]

On 06/27/2013 03:31 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.phogat at 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.

For release builds I don't think that we ever want to abort/exit.

I think the only time get_src_register_pointer() can return NULL is for 
the case of an invalid register file.  And we could instead return the 
ZeroVec there.

-Brian