nimforum mirror - passC only to C++ (clang++), not to C

I have nim C++ project (nim cpp --backend cpp to compile), having .c as an dependency.

If I passed --passC:"--std=c++17", clang causes error on compiling .c files.

Work-around is to rename .c into .cpp and wrap extern "C" { ... } whole the file, but I don't like use this...

Any way to pass compiler flag only to c++ compiler, not to c compiler?

separating flags into passC (for C files) and passCpp (for C++ files) is the standard, supported way to handle this I think,

You should try passCpp instead.


{.compile: ("myfile.cpp", "--std=c++17").}

{.passC.} adds the flags globally which is typically not what you want for compile.

@Ghazali Thank you! I didn't know "cpp.options.always" flag. I try this later!

@arnetheduck Thank you! I didn't know two-argument version of compile! However, I my case to many cpp files exist, so this would be messy...

I tried "cpp.options.always" on config.nims on windows vcc / clang_cl environment, but not worked.

so this would be messy

Typically, we solve this with a constant (it can also be done with a macro, but that's probably overkill):


const cppFlags = "--std=c++17"
{.compile: ("myfile.cpp", cppFlags).}

This is also useful for integrating third-party tools like pkg-config:


const SomePackageFlags = gorge "pkg-config --cflags SomePackage"
{.compile: ("myfile.cpp", SomePackageFlags).}

I mean you should use like based on compiler try this once:

switch("gcc.cpp.options.always", "-std=c++17")

switch("clang.cpp.options.always", "-std=c++17")

I confirmed cpp.options.always is working on UNIX enviroments.

--passC:"-std=c++17" causes problems on only UNIX environments, not windows (I don't know why), so I made conditional build flags to solve.


when defined(windows):
    switch("passC", "/std:c++17")
else:
    # switch("passC", "-std=c++17")
    switch("cpp.options.always", "-std=c++17")

Now I could {.compile: .c files mixed on .cpp files. Thank you very much.

Thank you, using constant on compile would be helpful in some case!

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