How to append static strings with FUNCTION in clang

Question

The following c++ code compiles fine with MSVC but doesn't compile with CLang.

void Test()
{
    auto str = __FUNCTION__ "." "Description";
}

why does this work for MSVC only? how do I make this work for clang? (. and Description can append without any issues in both compilers)

clang error: expected ';' at end of declaration

Note that "Test . Description" is not a solution, I want to use this in a macro and make static strings based on what function the macro is used in.

What version of CLang? What version of C++ did you tell CLang to use? — Thomas Matthews
– Thomas Matthews, Commented Nov 13, 2024 at 18:44
To be clear, that's not standard C++ code. The name __FUNCTION__, because it contains two consecutive underscores, is reserved for use by the implementation. Whatever it does is up to the compiler writer. So consult your compiler's documentation. — Pete Becker
– Pete Becker, Commented Nov 13, 2024 at 18:46
@ThomasMatthews here is godbolt demonstration godbolt.org/z/8T8G871G4 I use the latest version — M.kazem Akhgary
– M.kazem Akhgary, Commented Nov 13, 2024 at 18:47

3CEZVQ · Accepted Answer · 2024-11-13 21:26:22Z

0

If clang is run with -E, it can be seen that __FUNCTION__ is not a macro. This also was noticed in the comment with the linked answer: In C++, __FUNCTION__ and __PRETTY_FUNCTION__ have always been variables.

# 1 "/app/example.cpp"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 468 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "/app/example.cpp" 2

void Test()
{
    auto str = __FUNCTION__ ".Description";
}

You can make it like

#include <string>
using namespace std::string_literals;

void Test() {
  const auto str = __FUNCTION__ + ".Description"s;
}

answered Nov 13, 2024 at 21:26

3CEZVQ

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