Replacement of shader via glDetachShader + glAttachShader leads to link error

[10110111]

An OpenGL program (on Ubuntu 20.04 x86_64, Intel UHD Graphics 620) replaces a shader of a linked program by detaching an old shader and attaching a new one. When I apitrace it and then glretrace, things look correct unless I enable state dumping. If I enable state dumping, glLinkProgram fails after attaching the new shader in place of the old one with the following error:

9090 @0 glLinkProgram(program = 45)
9090: warning: link failed
9090: warning: error: function `main' is multiply defined

The reason for this behavior appears to be due to 5b14394. If I revert it, these unexpected errors no longer happen.

With the following trace (8.6MiB zipped) you can reproduce the problem using the following command:

glretrace -D 9090 stellarium.trace

stellarium.trace.zip

[jrfonseca]

Ah.... perhaps the !retrace::dumpingState condition should be replaced with not dumping state and not replacing?

Or perhaps shader replacing should ensure all shader sources are deleted before adding (at least when dumping state)?

[10110111]

The problem here is not in deletion, but rather in detaching. If you try to attach a shader with main() to a program that already has such a shader attached, you get multiple definition error. So I guess glDetachShader should be left alone.

My current workaround looks as follows, and I don't know of any reason how it could break (maybe you do?).

diff --git a/retrace/glretrace.py b/retrace/glretrace.py
index 19e994d3..4a891355 100644
--- a/retrace/glretrace.py
+++ b/retrace/glretrace.py
@@ -421,10 +421,6 @@ class GlRetracer(Retracer):
             print(r'    } else {')
             Retracer.invokeFunction(self, function)
             print(r'    }')
-        elif function.name in ('glDetachShader', 'glDetachObjectARB'):
-            print(r'    if (!retrace::dumpingState) {')
-            Retracer.invokeFunction(self, function)
-            print(r'    }')
         elif function.name == 'glClientWaitSync':
             print(r'    _result = glretrace::clientWaitSync(call, sync, flags, timeout);')
             print(r'    (void)_result;')