config: fix issues in weak symbol support - #7919
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There was an issue with icx support of weak symbols using #pragma weak. While the compile works, it will not properly honor the visibility attribute on the weak symbols. It does support weak symbols via attributes thoush. Potentially this is due to #pragma weak is separate from attributes in icx. Coincidentally, icx will raise error if the weak function is used within the compilation unit. Assumably, it treats the pragma weak declaration as an unresolved duplicate at compile time so it won't compile the function call within the unit. Anyway, that's how our previous release worked with icx, by accidentally prefer weak attribute against pragma weak. This commit restores the previous behavior as a work around for icx's bad support of #pragma weak.
colleeneb
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I built and tested on Sunspot and it built fine with intel. I confirmed the MPI symbols produced are global weak symbols. The macros defined in mpichconf.h match the older commit indeed: #define HAVE_ATTR_WEAK_ALIAS 1, /* #undef HAVE_MULTIPLE_PRAGMA_WEAK */, and /* #undef HAVE_PRAGMA_WEAK_ALIAS */.
For the record that I think the root cause of #pragma weak MPI_Foo = PMPI_Foo not working as expected is an Intel or clang bug and we reported it to Intel (argonne-lcf/AuroraBugTracking#153). So this could be reverted in the future once that is fixed.
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Pull Request Description
There was an issue with icx support of weak symbols using #pragma weak. While the compile works, it will not properly honor the visibility attribute on the weak symbols. It does support weak symbols via attributes thoush. Potentially this is due to #pragma weak is separate from attributes in icx.
Coincidentally, icx will raise error if the weak function is used within the compilation unit. Assumably, it treats the pragma weak declaration as an unresolved duplicate at compile time so it won't compile the function call within the unit.
Anyway, that's how our previous releas worked with icx, by accidentally prefer weak attribute against pragma weak.
This commit restors the previous behavior as a work around for icx's bad support of #pragma weak.
Credit to @colleeneb for bisecting releases and identifying key differences.
Fixes #7913
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