Discrepancy between what my application shows, and what the trace plays back (OpenGL)

[José Fonseca]

I see two possibilities:

- one is that the bug in PC1 OpenGL driver is a race condition,  enabling
debug checking changes the timing, hence makes things pass

- the other is that the bug is some sort of state validation issue, and the
glValidateProgram done by glretrace when checking errors, avoids the bug.

  I've seen this happening once.

  If this is the case, then this apitrace patch might get PC1 to draw
correctly even when not checking errors not selected:

diff --git a/retrace/glretrace.py b/retrace/glretrace.py
index 1e19473..a863c3c 100644
--- a/retrace/glretrace.py
+++ b/retrace/glretrace.py
@@ -280,7 +280,7 @@ class GlRetracer(Retracer):
            is_draw_arrays or \
            is_draw_elements or \
            function.name.startswith('glBeginTransformFeedback'):
-            print r'    if (retrace::debug) {'
+            print r'    if (1 || retrace::debug) {'
             print r'        _validateActiveProgram(call);'
             print r'    }'

@@ -571,7 +571,7 @@ _getActiveProgram(void)
 static void
 _validateActiveProgram(trace::Call &call)
 {
-    assert(retrace::debug);
+    //assert(retrace::debug);

     glretrace::Context *currentContext = glretrace::getCurrentContext();
     if (!currentContext ||



Jose

On Wed, Aug 12, 2015 at 2:38 PM, Babis Koniaris <esrever2357 at gmail.com>
wrote:

> Hi,
>
> I was looking onto a problem where my application displays what I expect
> on one PC (PC0) and exhibits a bug on another (PC1). PC0 has a nice
> powerful Geforce TITAN, while PC1 is a laptop intel integrated card. I'm
> running an application on OpenGL 4.00 (GLSL 4.00) which is supported on
> both.
>
> The problem lies with reading the contents of a particular texture
> (R16UI): on PC1 the shader always reads zeroes, while on PC0 it reads the
> values normally. There are no OpenGL errors. Here is when I decided to run
> apitrace to find out what's going on.
>
> I run qapitrace (latest version) and exit the application after a while,
> all while seeing the problem. I hit replay, and *the trace plays
> correctly, as in PC0. *After a bit of fiddling, I realized that if, in
> the Replay menu, "Error Checking" is selected, then the trace plays
> correctly as in PC0. If it's not selected, then it shows the bug as usual.
>
> What could be going on?
>
> Thanks,
> Babis
>
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>
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