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Windows: support more Mingw-w64 versions #2578

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Windows: support more Mingw-w64 versions #2578

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11 changes: 8 additions & 3 deletions config.nims
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Expand Up @@ -57,10 +57,15 @@ else:
switch("passC", "-mno-avx512f")
switch("passL", "-mno-avx512f")

# omitting frame pointers in nim breaks the GC
# Omitting frame pointers in nim breaks the GC:
# https://github.com/nim-lang/Nim/issues/10625
switch("passC", "-fno-omit-frame-pointer")
switch("passL", "-fno-omit-frame-pointer")
if not defined(windows):
# ...except on Windows where the Nim bug doesn't manifest and this option
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@zah zah May 27, 2021 •
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Why wouldn't the Nim bug manifest on Windows?

This is not a frequently appearing bug, but a theoretical risk in the way the conservative stack scanning is implemented that might result in a crash that would be extremely hard to track down.

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No pointer mangling in the Mingw version of glibc. See this issue for the mechanism: nim-lang/Nim#10625

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Can you point me to the documentation regarding the lack of pointer mangling in mingw? Perhaps there is some compile-time assertions that can added to the code to verify that.

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Glibc setjmp implementation, with mangling: https://github.com/lattera/glibc/blob/895ef79e04a953cac1493863bcae29ad85657ee1/sysdeps/x86_64/setjmp.S#L33

Mingw-w64 setjmp implementation, without any mangling: https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-crt/misc/setjmp.S

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A check for the definition of PTR_MANGLE would be a good additional precaution - it could be added at the bottom of the main nim module:

{.emit: """

#ifdef ASSUME_NO_PTR_MANGLE
#ifdef PTR_MANGLE
#error "This build assumes that pointer mangling is disabled. See config.nims for details"
#endif
#endif

""".}

# crashes GCC in some Mingw-w64 versions:
# https://sourceforge.net/p/mingw-w64/bugs/880/
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86593
switch("passC", "-fno-omit-frame-pointer")
switch("passL", "-fno-omit-frame-pointer")

--threads:on
--opt:speed
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