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<p class="MsoNormal">Hello Lucas,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We observe two issues regarding your commits “[Clang][Sema] Capturing section type conflicts between #pragma clang section”:<o:p></o:p></p>
<p class="MsoNormal"><a href="https://github.com/llvm/llvm-project/commit/0dac639f285a53dffe3239ec5561fa0fc2da0daf">https://github.com/llvm/llvm-project/commit/0dac639f285a53dffe3239ec5561fa0fc2da0daf</a><o:p></o:p></p>
<p class="MsoNormal"><a href="https://github.com/llvm/llvm-project/commit/9d39df03a984ff4bed7d441a110d44976a8ab21b">https://github.com/llvm/llvm-project/commit/9d39df03a984ff4bed7d441a110d44976a8ab21b</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A first observation is that once a section has been used as bss argument in a #pragma clang section, it is no longer possible to use this section in an explicit section annotation on a variable, even if this variable is zero-initialized:<o:p></o:p></p>
<p class="MsoNormal"><a href="https://godbolt.org/z/oiNHk3">https://godbolt.org/z/oiNHk3</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[ In contrast, for a section used as the rodata argument, you *can* still do this, provided that the variable is “const”:<o:p></o:p></p>
<p class="MsoNormal"><a href="https://godbolt.org/z/wJvYiW">https://godbolt.org/z/wJvYiW</a> ]<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The problem for bss sections seems to be related to the newly introduced “<span class="blob-code-inner">PSF_ZeroInit</span>” flag?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A second issue is that #pragma clang section provided a way to assign multiple variables to the same data section, mixing const, non-const and zero-initialized variables. When using an explicit section attribute, clang and gcc disallow
to use the same section for const and non-const variables: <a href="https://godbolt.org/z/S76vKm">
https://godbolt.org/z/S76vKm</a> (but you can mix zero-initialized and non-zero-initialized variables)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">An implicit section annotation using #pragma clang section allowed to work around this, by specifying the same data section in the pragma:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> #pragma clang section data=”mydata” bss=”mydata” rodata=”mydata”<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This is an example using clang-10: <a href="https://godbolt.org/z/vxty7T">
https://godbolt.org/z/vxty7T</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This is now rejected, and granted, it was an abuse of the #pragma clang section. But is it not valid to assign both const and non-const variables to the same data section? Either with an explicit annotation or implicit?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Bruno De Fraine<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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