Mangling extension for C++20 Modules #134
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urnathan
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The existing module symbol mangling scheme turns out to be undemangleable. It is also desirable to switch to the strong-ownership model as the hoped-for C++17 compatibility turns out to be fragile, and we also now have a better way of controlling that. The issue is captured on the ABI list at: itanium-cxx-abi/cxx-abi#134 A document describing the issues and new mangling is at: https://drive.google.com/file/d/1qQjqptzOFT_lfXH8L6-iD9nCRi34wjft/view This patch is the code-generation part. I have a demangler too, but that patch is based on some to-be-landed refactoring of the demangler. The old mangling is unceremoniously dropped. No backwards compatibility, no deprectated old-mangling flag. It was always labelled experimental. (Old and new manglings cannot be confused.) Reviewed By: ChuanqiXu Differential Revision: https://reviews.llvm.org/D118352
urnathan
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Implement a demangleable strong ownership symbol mangling. * The original module symbol mangling scheme turned out to be undemangleable. * The hoped-for C++17 compatibility of weak ownership turns out to be fragile * C++20 now has better ways of controlling C++17 compatibility The issue is captured on the ABI list at: itanium-cxx-abi/cxx-abi#134 GCC implements this new mangling. The old mangling is unceremoniously dropped. No backwards compatibility, no deprectated old-mangling flag. It was always labelled experimental. (Old and new manglings cannot be confused.) Reviewed By: dblaikie Differential Revision: https://reviews.llvm.org/D122256
mem-frob
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Implement a demangleable strong ownership symbol mangling. * The original module symbol mangling scheme turned out to be undemangleable. * The hoped-for C++17 compatibility of weak ownership turns out to be fragile * C++20 now has better ways of controlling C++17 compatibility The issue is captured on the ABI list at: itanium-cxx-abi/cxx-abi#134 GCC implements this new mangling. The old mangling is unceremoniously dropped. No backwards compatibility, no deprectated old-mangling flag. It was always labelled experimental. (Old and new manglings cannot be confused.) Reviewed By: dblaikie Differential Revision: https://reviews.llvm.org/D122256
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the referenced google document
hello, the referenced google document is not reachable anymore. was it moved / removed ?
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@urnathan hi, would you like to send the documentation again? This is somewhat embrassing that the implementation were already merged into GCC and Clang but the document doesn't merge into the Itanium C++ ABI specification... so they is the status quo standard now. I think it may be better to summarize them into the ABI specification formally. CC @rjmccall I found this when I try to summarize the ABI related things with modules |
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On 1/11/24 01:58, Chuanqi Xu wrote:
@urnathan <https://github.com/urnathan> hi, would you like to send the
documentation again? This is somewhat embrassing that the implementation were
already merged into GCC and Clang but the document doesn't merge into the
Itanium C++ ABI specification... so they is the status quo standard now. I think
it may be better to summarize them into the ABI specification formally.
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Both GCC and Clang added mangling for c++20 module purview symbols. While we tried to do the same thing, we failed :( It also turns out the scheme we designed is undemangleable. Plus the modules-ts evolved.
Here is a newer scheme: https://drive.google.com/file/d/1qQjqptzOFT_lfXH8L6-iD9nCRi34wjft/view?usp=sharing
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