Improvements to the pkg-config file #26
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When m4ri is compiled with PNG support, it exposes the two new symbols mzd_from_png and mzd_to_png via m4ri/io.h. But neither of those functions takes any libpng types as an argument, and so a program being linking against m4ri should not need to include -lpng in its link flags.
The -fopenmp (or equivalent) flag should not be present in Cflags, because it causes programs being linked against m4ri to be compiled with OpenMP support, and that may not be intended. For example, this causes runtime crashes in SageMath built with meson: while -fopenmp from m4ri is used at compile time, libgomp is ultimately not linked in because the build system doesn't think we're using OpenMP. As a result, $OPENMP_FLAGS flags are more appropriate to include when linking than compiling. Moreover, the OpenMP library dependency (on libgomp or equivalent) should be private for the same reason libpng is: none of its symbols are directly exposed to users of m4ri.
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Why do you still keep libpng's cflags in? |
If the |
dimpase
approved these changes
Jan 22, 2025
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OK |
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Thanks! |
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Two small improvements to
m4ri.pc:libpng becomes an internal (
Requires.private) dependency. I've looked at the code, and I don't think any symbols from libpng are leaked to consumers. In other words, someone linking their program to m4ri does not need to supply-lpng. This change prevents the-lpngfrom being output bypkg-config --libs m4ri.The OpenMP flags are applied to static linking only. This was my original motivation for digging into this file. My copy of sage was being compiled (but not linked!) with
-fopenmpbecause that flag appears in the pkg-config output for m4ri. The result of course crashes due to missing libgomp symbols. TheOPENMP_FLAGSare applied to linking to (only) to avoid this issue, and made private for the same reason we made libpng private.Resolves:
CC: @kiwifb, @dimpase, @tornaria, @arojas, @isuruf