Fix race condition in Switch_DeleteShader initialization #28044
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| DeleteShader = (PFNDELETESHADERPROC)IntGetProcAddress("glDeleteShader"); | ||
| static std::once_flag flag; | ||
| std::call_once(flag, []() { | ||
| DeleteShader = (PFNDELETESHADERPROC)IntGetProcAddress("glDeleteShader"); |
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Can we use static DeleteShader?
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i will think on it
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Can we use
staticDeleteShader?
static local variable to solve this, because it breaks the "Self-Patching" optimization that this code relies on. Initial State: The global pointer DeleteShader points to the helper function Switch_DeleteShader.
First Call: You call DeleteShader(id). It goes to Switch_DeleteShader.
The Patch: Switch_DeleteShader finds the real driver address and overwrites the global DeleteShader variable.
Future Calls: The next time you call DeleteShader(id), the global variable now points directly to the driver. It skips Switch_DeleteShader entirely.
If change the code to use a static local variable
C++
// BAD APPROACH for this specific architecture
static void Switch_DeleteShader(GLuint shader)
{
// This is thread-safe (C++11 magic statics), BUT...
static PFNDELETESHADERPROC real_func = (PFNDELETESHADERPROC)IntGetProcAddress("glDeleteShader");
real_func(shader);
}
The Problem: This code never updates the global DeleteShader pointer.
Result: gl::DeleteShader will always point to Switch_DeleteShader.
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Also the same approach with static local variable should be applied to all OpenGL functions in the file. |
i will try |
i edited all 245 fuctions please check my changed function and also give review where i have to improve |
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@asmorkalov can you review it , thank you for your time |
Summary
This PR resolves a race condition in the OpenGL loader reported in issue #27965. When multiple threads called Switch_DeleteShader simultaneously, the global function pointer assignment was not synchronized, leading to potential crashes or undefined behavior.
Changes Made
Modified modules/core/src/gl_core_3_1.cpp.
Included the header.
Implemented std::once_flag and std::call_once inside Switch_DeleteShader to ensure the function pointer is initialized exactly once in a thread-safe manner.