cc-rs: Compiler version doesn't include clang or GCC: "cc" "--version"

For everyone subscribing, #1000 should fix this and once it is merged, I will cut a new release.

Thanks, I will work on a patch once I fixed the make problem.

The standard way to check what version of compiler you have is to analyze the preprocessor definitions defined by the compiler for a trivial program. Simply relying on the output of --version is never used in any sane C++ build system.

For instance, CMake looks at preprocessor definitions emitted by the compiler to detect compiler versions. It’s usually pretty complex for the more difficult compilers, but this is more reasonable than relying on inspecting the output of --version. Note: you would have to check clang before gcc since clang pretends to be gcc.

Clang:

$ /bin/cat /usr/share/cmake/Modules/Compiler/Clang-DetermineCompiler.cmake

set(_compiler_id_pp_test "defined(__clang__)")

include("${CMAKE_CURRENT_LIST_DIR}/Clang-DetermineCompilerInternal.cmake")

GCC:

$ /bin/cat /usr/share/cmake/Modules/Compiler/GNU-CXX-DetermineCompiler.cmake

set(_compiler_id_pp_test "defined(__GNUC__) || defined(__GNUG__)")

set(_compiler_id_version_compute "
# if defined(__GNUC__)
#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__GNUC__)
# else
#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__GNUG__)
# endif
# if defined(__GNUC_MINOR__)
#  define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__GNUC_MINOR__)
# endif
# if defined(__GNUC_PATCHLEVEL__)
#  define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__GNUC_PATCHLEVEL__)
# endif")

Ok I decided to use the following .c file for detecting compiler family:

#ifdef __clang__
# pragma message "clang"
#else

# ifdef __GNUC__
#  pragma message "gcc"
# endif

# ifdef _MSC_VER
#  pragma message "msvc"
# endif
#endif

Tested with clang, apple clang and gcc on macOS, mingw gcc and msvc on windows

I don’t know Rust and have never seen this repo before, but it’s affecting some third-party software I’m using that needs this library. (I am, however, very familiar with C/C++.)

Since we’re invoking the compiler to begin with, perhaps we could do a little more work to get something more reliable? For example, we could compile and run a small program like this:

#ifdef __cplusplus
#    include <cstdio>
#else
#    include <stdio.h>
#endif

int main() {
    /* Always check Clang before __GNUC__ because it defines that too */
#ifdef __clang__
    printf("clang | %s\n", __clang_version__);
    return 0;
#endif

#ifdef __GNUC_VERSION__
    /* Could be TCC or another compiler professing compatibility, so we may need
       to do further checks, especially if we're choosing CLI arguments based on
       the compiler and version. */
    printf(
        "GCC | %d.%d.%d\n",
        __GNUC_VERSION__ / 10000,
        __GNUC_VERSION__ / 100,
        __GNUC_VERSION__ % 100
    );
    return 0;
#endif

#ifdef _MSC_VER
    printf("MSVC | %d.%d\n", _MSC_VER / 100, _MSC_VER % 100);
    return 0;
#endif

    /* Unrecognized compiler */
    return 1;
}

We could get detailed information from this, such as the width of int and so on. Since we completely control the output, we could construct JSON if we wanted to.

I’ve found this list highly useful for compiler detection. There are other lists for detecting OS and host/target architecture.

Waiting for #1015 to merge

Tested Clang and GCC on Ubuntu 23.10 and it works. Thanks!

I’m seeing this too

❯ c++ --version
c++ (Gentoo 13.2.1_p20240113-r1 p12) 13.2.1 20240113
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.