[Mesa-dev] glxinfo proposed change

[Jorge Ramirez Ortiz, HCL Europe]

>-----Original Message-----
>From: Dan Nicholson [mailto:dbn.lists at gmail.com]
>Sent: Monday, January 07, 2013 2:31 PM
>To: Jorge Ramirez Ortiz, HCL Europe
>Cc: mesa-dev at lists.freedesktop.org
>Subject: Re: [Mesa-dev] glxinfo proposed change
>
>On Mon, Jan 7, 2013 at 5:06 AM, Jorge Ramirez Ortiz,  HCL Europe
><Jorge.Ramirez-Ortiz at hcl.com> wrote:
>> Hi all,
>>
>> Does this patch make sense? glVersion can be NULL and not having the
>changes below could cause a SIGSEGV
>>
>> [jramirez at calypso-2 mesa-demos.git (tmp *)]$ git diff src/xdemos/glxinfo.c
>> diff --git a/src/xdemos/glxinfo.c b/src/xdemos/glxinfo.c
>> index aa6430d..97b6539 100644
>> --- a/src/xdemos/glxinfo.c
>> +++ b/src/xdemos/glxinfo.c
>> @@ -639,7 +639,7 @@ print_screen_info(Display *dpy, int scrnum, Bool
>allowDirect, Bool limits, Bool
>>        printf("OpenGL renderer string: %s\n", glRenderer);
>>        printf("OpenGL version string: %s\n", glVersion);
>>  #ifdef GL_VERSION_2_0
>> -      if (glVersion[0] >= '2' && glVersion[1] == '.') {
>> +      if (glVersion && glVersion[0] >= '2' && glVersion[1] == '.') {
>>           char *v = (char *) glGetString(GL_SHADING_LANGUAGE_VERSION);
>>           printf("OpenGL shading language version string: %s\n", v);
>>        }
>
>Normally, this is a good idea. However, glVersion is already
>dereferenced in the printf on the previous line. So, any actual
>checking for NULL glVersion should at least come earlier in the
>function. On the other hand, returning NULL from
>glGetString(GL_VERSION) might be so rare that bothering to guard for
>it would be more effort than it's worth.
>

Bear in mind that printf of a null string wont SIGSEGV. 
Only trying to access glVersion[] elements presents -and indeed is - a risk and therefore a critical bug (for my usual standards that is).





>--
>Dan


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