llvm/llvm-project

#pragma init_seg(section-specifier, func-name) not supported

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#148,938 opened on Jul 15, 2025

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clang:frontendextension:microsoftgood first issueplatform:windows

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Description

This MSVC pragma is only partially implemented. As detailed here, there is functionality to specify a function to call in place of atexit.

https://learn.microsoft.com/en-us/cpp/preprocessor/init-seg?view=msvc-170

"func-name Specifies a function to be called in place of atexit when the program exits. This helper function also calls atexit with a pointer to the destructor for the global object. If you specify a function identifier in the pragma of the form,

C++

Copy int __cdecl myexit (void (__cdecl *pf)(void)) then your function will be called instead of the C run-time library's atexit. It allows you to build a list of the destructors to call when you're ready to destroy the objects."

Relevant code in ParsePragma.cpp:Parser::HandlePragmaMSInitSeg: // FIXME: Add support for the '[, func-name]' part of the pragma.

Maybe a good early OSS contribution given the limited use and lack of potential for regression

Contributor guide

Research direction
Examine the existing implementation of HandlePragmaMSInitSeg in ParsePragma.cpp to understand the current partial support, then add the func name parameter handling as described in the MSVC documentation.
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2
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1-3 hours
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65