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patch to __attribute__ ((visibility ("default"))) on exported functions by mattip · Pull Request #241 · MacPython/openblas-libs · GitHub

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patch to __attribute__ ((visibility ("default"))) on exported functions - #241

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patch to __attribute__ ((visibility ("default"))) on exported functions#241
mattip wants to merge 6 commits into
MacPython:mainfrom
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mattip commented Dec 10, 2025 •
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  • I updated the package version in pyproject.toml and made sure the first 3 numbers match git describe --tags --abbrev=8 in OpenBLAS at the OPENBLAS_COMMIT. If I did not update OPENBLAS_COMMIT, I incremented the wheel build number (i.e. 0.3.29.0.0 to 0.3.29.0.1)

This is a proof of concept that works to hide functions from exposing them from the shared object on posix

  • Use CFLAGS+=-fvisibility=hidden to hide by default
  • Add __attribute__ ((visibility ("default"))) in all the exported function definitions
  • Use NO_LAPACKE=1 to avoid building (and exporting) legacy lapack routines Add a filter-out for -fvisibility=hidden in the lapacke Makefiles

For me this solves numpy/numpy#30299, it no longer segfaults. Although when I look at ltrace I still see that a global openblas is overriding the function dgemm_kernel_HASWELL in the call to scipy_cblas_dgemm64_ at NumPy import.

mattip mentioned this pull request Dec 10, 2025
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mattip commented Dec 11, 2025

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global openblas is overriding the function dgemm_kernel_HASWELL

I added the hidden directive to the PROLOGUE macro for assembler code, and in doing so discovered that there is assembler code for

  • int lsame(char *a, char *b) which compares *a == *b
  • FLOAT cabs(FLOAT *a) which does fabs(a[0]) + fabs(a[1]).

Both these functions have generic equivalents in the kernels/generics directory, and I checked on Compiler Explorer that modern compilers generate equivalent assembler to the hand-created assembler in the non-generic directories. So rather than create a special non-hidden assembler PROLOGUE macro, I set the build to use the generic C versions, which can easily be marked with the visible attribute.

This was referenced Dec 12, 2025
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mattip mentioned this pull request Dec 22, 2025
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mattip commented Dec 22, 2025

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In the upstream PR, I defined a new PROLOGUE_EXPORT macro and used it rather than using the generic kernels for lsame and cabs.

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