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Pass C++ environment variables to configure scripts #10797

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Ericson2314 opened this issue Feb 20, 2025 · 1 comment · May be fixed by #10844
Open

Pass C++ environment variables to configure scripts #10797

Ericson2314 opened this issue Feb 20, 2025 · 1 comment · May be fixed by #10844
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type: enhancement

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@Ericson2314
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Describe the feature request

Since Cabal has some support for C++ (cxx-options, cxx-sources), I think we should also support passing standard C++ toolchain environment variables to the configure script analogously to how we do with C:

cabal/Cabal/src/Distribution/Simple/ConfigureScript.hs

Lines 171 to 177 in 595d023

overEnv =
("CFLAGS", Just cflagsEnv)
: [("PATH", Just pathEnv) | not (null extraPath)]
++ cabalFlagEnv
maybeHostFlag = if hp == buildPlatform then [] else ["--host=" ++ show (pretty hp)]
args' = configureFile' : args ++ ["CC=" ++ ccProgShort] ++ maybeHostFlag
shProg = simpleProgram "sh"

I think this would be

  • CXX (like CC)
  • CXXFLAGS (like CFLAGS)

Additional context

This came up in https://gitlab.haskell.org/ghc/ghc/-/issues/25767#note_610831
@mpickering
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I have implemented this, but I'm not sure why we set the CFLAGS environment variable but pass CC as an argument. I just copied this rather than change anything.

mpickering added a commit that referenced this issue Mar 21, 2025
@mpickering
Pass CXX and CXXFLAGS argument to ./configure scripts for build-type:…
4dbb260 
… Configure

Since the compiler since ghc-9.4.8 requires a C++ toolchain, and that is
configured into the compiler --info, it makes sense to pass that
information onto the ./configure script.

The assumption that the C++ compiler is part of the toolchain is only
since ghc-9.4. Therefore, if no C++ compiler is found, then the options
won't be passed to the configure script.

For compilers older than 9.4, the C++ compiler will always be found as
it is configured into the settings file.

See https://gitlab.haskell.org/ghc/ghc/-/issues/25767#note_610831 for
some discussion about how this would be useful to implement
system-cxx-std-lib in userspace.

Fixes #10797
@mpickering mpickering linked a pull request Mar 21, 2025 that will close this issue
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mpickering added a commit that referenced this issue Mar 21, 2025
@mpickering
Pass CXX and CXXFLAGS argument to ./configure scripts for build-type:…
9c1f75e 
… Configure

Since the compiler since ghc-9.4.8 requires a C++ toolchain, and that is
configured into the compiler --info, it makes sense to pass that
information onto the ./configure script.

The assumption that the C++ compiler is part of the toolchain is only
since ghc-9.4. Therefore, if no C++ compiler is found, then the options
won't be passed to the configure script.

For compilers older than 9.4, the C++ compiler will always be found as
it is configured into the settings file.

See https://gitlab.haskell.org/ghc/ghc/-/issues/25767#note_610831 for
some discussion about how this would be useful to implement
system-cxx-std-lib in userspace.

Fixes #10797
mpickering added a commit that referenced this issue Mar 21, 2025
@mpickering
Pass CXX and CXXFLAGS argument to ./configure scripts for build-type:…
743adf3 
… Configure

Since the compiler since ghc-9.4.8 requires a C++ toolchain, and that is
configured into the compiler --info, it makes sense to pass that
information onto the ./configure script.

The assumption that the C++ compiler is part of the toolchain is only
since ghc-9.4. Therefore, if no C++ compiler is found, then the options
won't be passed to the configure script.

For compilers older than 9.4, the C++ compiler will always be found as
it is configured into the settings file.

See https://gitlab.haskell.org/ghc/ghc/-/issues/25767#note_610831 for
some discussion about how this would be useful to implement
system-cxx-std-lib in userspace.

Fixes #10797
mpickering added a commit that referenced this issue Mar 24, 2025
@mpickering
Pass CXX and CXXFLAGS argument to ./configure scripts for build-type:…
5c7911b 
… Configure

Since the compiler since ghc-9.4.8 requires a C++ toolchain, and that is
configured into the compiler --info, it makes sense to pass that
information onto the ./configure script.

The assumption that the C++ compiler is part of the toolchain is only
since ghc-9.4. Therefore, if no C++ compiler is found, then the options
won't be passed to the configure script.

For compilers older than 9.4, the C++ compiler will always be found as
it is configured into the settings file.

See https://gitlab.haskell.org/ghc/ghc/-/issues/25767#note_610831 for
some discussion about how this would be useful to implement
system-cxx-std-lib in userspace.

Fixes #10797
mpickering added a commit that referenced this issue Mar 24, 2025
@mpickering
Pass CXX and CXXFLAGS argument to ./configure scripts for build-type:…
482ad79 
… Configure

Since the compiler since ghc-9.4.8 requires a C++ toolchain, and that is
configured into the compiler --info, it makes sense to pass that
information onto the ./configure script.

The assumption that the C++ compiler is part of the toolchain is only
since ghc-9.4. Therefore, if no C++ compiler is found, then the options
won't be passed to the configure script.

For compilers older than 9.4, the C++ compiler will always be found as
it is configured into the settings file.

See https://gitlab.haskell.org/ghc/ghc/-/issues/25767#note_610831 for
some discussion about how this would be useful to implement
system-cxx-std-lib in userspace.

Fixes #10797
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Pass CXX and CXXFLAGS argument to ./configure scripts for build-type: Configure haskell/cabal
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@Ericson2314 @mpickering