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

[zh-jq-b]

On Debian Sid:
Output of cc --version, which is different from gcc --version:

cc (Debian 13.2.0-13) 13.2.0
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.

Output of cc -v, which is the same as gcc -v:

Using built-in specs.
COLLECT_GCC=cc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-linux-gnu/13/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 13.2.0-13' --with-bugurl=file:///usr/share/doc/gcc-13/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-13 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/libexec --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-libstdcxx-backtrace --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/reproducible-path/gcc-13-13.2.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/reproducible-path/gcc-13-13.2.0/debian/tmp-gcn/usr --enable-offload-defaulted --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.2.0 (Debian 13.2.0-13) 

So it's may be better to use -v to check the compiler type?

[NobodyXu]

That may be a good idea, however I'm not sure how it affects msvc and other compilers.

[Be-ing]

I am also seeing this on GitHub Actions' Ubuntu 22.04 runner: https://github.com/KDAB/cxx-qt/actions/runs/7986404801/job/21806762461?pr=848#step:14:93

I cannot reproduce the warning locally on Fedora 39.

[edg-l]

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.

[willkill07]

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")

[NobodyXu]

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

[NobodyXu]

Ok so for clang we can use:

#define XSTR(x) STR(x)
#define STR(x) #x

#pragma message "COMPILER_VERSION_MAJOR = " XSTR(__clang_major__)
#pragma message "COMPILER_VERSION_MINOR = " XSTR(__clang_minor__)
#pragma message "COMPILER_VERSION_PATCH = " XSTR(__clang_patchlevel__)


#if defined(_MSC_VER)
  /* _MSC_VER = VVRR */
# pragma message "SIMULATE_VERSION_MAJOR = " XSTR(_MSC_VER / 100)
# pragma message "SIMULATE_VERSION_MINOR = " XSTR(_MSC_VER % 100)
#endif

#if defined(_MSC_VER)
# pragma message "SIMULATE_ID = MSVC"
#endif

on my macOS system, using the homebrew clang, clang -c a.c gives me:

a.c:4:9: warning: COMPILER_VERSION_MAJOR = 17 [-W#pragma-messages]
    4 | #pragma message "COMPILER_VERSION_MAJOR = " XSTR(__clang_major__)
      |         ^
a.c:5:9: warning: COMPILER_VERSION_MINOR = 0 [-W#pragma-messages]
    5 | #pragma message "COMPILER_VERSION_MINOR = " XSTR(__clang_minor__)
      |         ^
a.c:6:9: warning: COMPILER_VERSION_PATCH = 6 [-W#pragma-messages]
    6 | #pragma message "COMPILER_VERSION_PATCH = " XSTR(__clang_patchlevel__)
      |         ^
3 warnings generated.

Using the gcc imposted by apple clang, gcc -c a.c (cc -c a.c gives the same output):

a.c:4:9: warning: COMPILER_VERSION_MAJOR = 15 [-W#pragma-messages]
#pragma message "COMPILER_VERSION_MAJOR = " XSTR(__clang_major__)
        ^
a.c:5:9: warning: COMPILER_VERSION_MINOR = 0 [-W#pragma-messages]
#pragma message "COMPILER_VERSION_MINOR = " XSTR(__clang_minor__)
        ^
a.c:6:9: warning: COMPILER_VERSION_PATCH = 0 [-W#pragma-messages]
#pragma message "COMPILER_VERSION_PATCH = " XSTR(__clang_patchlevel__)
        ^
3 warnings generated.

Running real gcc, gcc-13 -c a.c:

a.c:4:9: note: '#pragma message: COMPILER_VERSION_MAJOR = __clang_major__'
    4 | #pragma message "COMPILER_VERSION_MAJOR = " XSTR(__clang_major__)
      |         ^~~~~~~
a.c:5:9: note: '#pragma message: COMPILER_VERSION_MINOR = __clang_minor__'
    5 | #pragma message "COMPILER_VERSION_MINOR = " XSTR(__clang_minor__)
      |         ^~~~~~~
a.c:6:9: note: '#pragma message: COMPILER_VERSION_PATCH = __clang_patchlevel__'
    6 | #pragma message "COMPILER_VERSION_PATCH = " XSTR(__clang_patchlevel__)
      |         ^~~~~~~

Same output when using clang++, c++, g++, for g++-13 though g++-13 -c a.c gives:

a.c:4:65: note: '#pragma message: COMPILER_VERSION_MAJOR = __clang_major__'
    4 | #pragma message "COMPILER_VERSION_MAJOR = " XSTR(__clang_major__)
      |                                                                 ^
a.c:2:17: note: in definition of macro 'STR'
    2 | #define STR(x) #x
      |                 ^
a.c:4:45: note: in expansion of macro 'XSTR'
    4 | #pragma message "COMPILER_VERSION_MAJOR = " XSTR(__clang_major__)
      |                                             ^~~~
a.c:5:65: note: '#pragma message: COMPILER_VERSION_MINOR = __clang_minor__'
    5 | #pragma message "COMPILER_VERSION_MINOR = " XSTR(__clang_minor__)
      |                                                                 ^
a.c:2:17: note: in definition of macro 'STR'
    2 | #define STR(x) #x
      |                 ^
a.c:5:45: note: in expansion of macro 'XSTR'
    5 | #pragma message "COMPILER_VERSION_MINOR = " XSTR(__clang_minor__)
      |                                             ^~~~
a.c:6:70: note: '#pragma message: COMPILER_VERSION_PATCH = __clang_patchlevel__'
    6 | #pragma message "COMPILER_VERSION_PATCH = " XSTR(__clang_patchlevel__)
      |                                                                      ^
a.c:2:17: note: in definition of macro 'STR'
    2 | #define STR(x) #x
      |                 ^
a.c:6:45: note: in expansion of macro 'XSTR'
    6 | #pragma message "COMPILER_VERSION_PATCH = " XSTR(__clang_patchlevel__)
      |                                             ^~~~

[NobodyXu]

For GCC:

#define XSTR(x) STR(x)
#define STR(x) #x

#if defined(__GNUC__)
# pragma message "COMPILER_VERSION_MAJOR = " XSTR(__GNUC__)
#else
# pragma message "COMPILER_VERSION_MAJOR = " XSTR(__GNUG__)
#endif

#if defined(__GNUC_MINOR__)
# pragma message "COMPILER_VERSION_MINOR = " XSTR(__GNUC_MINOR__)
#endif

#if defined(__GNUC_PATCHLEVEL__)
# pragma message "COMPILER_VERSION_PATCH = " XSTR(__GNUC_PATCHLEVEL__)
#endif

For gcc-13 -c b.c:

b.c:5:10: note: '#pragma message: COMPILER_VERSION_MAJOR = 13'
    5 | # pragma message "COMPILER_VERSION_MAJOR = " XSTR(__GNUC__)
      |          ^~~~~~~
b.c:11:10: note: '#pragma message: COMPILER_VERSION_MINOR = 2'
   11 | # pragma message "COMPILER_VERSION_MINOR = " XSTR(__GNUC_MINOR__)
      |          ^~~~~~~
b.c:15:10: note: '#pragma message: COMPILER_VERSION_PATCH = 0'
   15 | # pragma message "COMPILER_VERSION_PATCH = " XSTR(__GNUC_PATCHLEVEL__)
      |          ^~~~~~~

g++-13 -c b.c:

b.c:5:59: note: '#pragma message: COMPILER_VERSION_MAJOR = 13'
    5 | # pragma message "COMPILER_VERSION_MAJOR = " XSTR(__GNUC__)
      |                                                           ^
b.c:2:17: note: in definition of macro 'STR'
    2 | #define STR(x) #x
      |                 ^
b.c:5:46: note: in expansion of macro 'XSTR'
    5 | # pragma message "COMPILER_VERSION_MAJOR = " XSTR(__GNUC__)
      |                                              ^~~~
b.c:11:65: note: '#pragma message: COMPILER_VERSION_MINOR = 2'
   11 | # pragma message "COMPILER_VERSION_MINOR = " XSTR(__GNUC_MINOR__)
      |                                                                 ^
b.c:2:17: note: in definition of macro 'STR'
    2 | #define STR(x) #x
      |                 ^
b.c:11:46: note: in expansion of macro 'XSTR'
   11 | # pragma message "COMPILER_VERSION_MINOR = " XSTR(__GNUC_MINOR__)
      |                                              ^~~~
b.c:15:70: note: '#pragma message: COMPILER_VERSION_PATCH = 0'
   15 | # pragma message "COMPILER_VERSION_PATCH = " XSTR(__GNUC_PATCHLEVEL__)
      |                                                                      ^
b.c:2:17: note: in definition of macro 'STR'
    2 | #define STR(x) #x
      |                 ^
b.c:15:46: note: in expansion of macro 'XSTR'
   15 | # pragma message "COMPILER_VERSION_PATCH = " XSTR(__GNUC_PATCHLEVEL__)
      |                                              ^~~~

For clang, clang++ and clang-imposed cc, c++, gcc, g++ , they all give version 4.2.0 on my machine.

[NobodyXu]

TODO for myself: Also test zig-cc output

Would also be great to test different compilers in CI

[NobodyXu]

Output of zig cc and zig c++ is basically the same as clang and clang++, only way of telling the difference is by running zig cc --version/zig cc -v which gives:

clang version 16.0.6 (https://github.com/ziglang/zig-bootstrap 1dda86241204c4649f668d46b6a37feed707c7b4)
Target: aarch64-unknown-darwin23.2.0
Thread model: posix
InstalledDir: /usr/bin

slightly different from clang -v

[dargueta]

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.

[NobodyXu]

Thanks @dargueta I would open a PR for this soon.

[dargueta]

Don't copy and paste that, I just noticed a bug (missing return statements).

[NobodyXu]

I will probably just use the macro-only and use -E to only run pre-processing.