Compilation with FMTLOG_HEADER_ONLY

[paLeziart]

Hi 👋 ,

I just wanted to provide some feedback in case someone encounters an issue similar to mine when trying to compile with FMTLOG_HEADER_ONLY.

For reference, I installed fmtlib through sudo apt install libfmt-dev on Linux Mint 21.3.

I tried to compile the following minimal example with g++ -std=c++17 -o myprogram source.cpp.

#define FMTLOG_HEADER_ONLY

#include "fmtlog.h"

int main() 
{
  FMTLOG(fmtlog::INF, "The answer is {}.", 42);
}

which fails with a ton of errors like

/usr/bin/ld: /tmp/ccpnEvRi.o: in function `std::make_unsigned<int>::type fmt::v8::detail::to_unsigned<int>(int)':
source.cpp:(.text._ZN3fmt2v86detail11to_unsignedIiEENSt13make_unsignedIT_E4typeES4_[_ZN3fmt2v86detail11to_unsignedIiEENSt13make_unsignedIT_E4typeES4_]+0x23): undefined reference to `fmt::v8::detail::assert_fail(char const*, int, char const*)'

The solution for successfull compilation is to also define the FMT_HEADER_ONLY macro.

#define FMT_HEADER_ONLY
#define FMTLOG_HEADER_ONLY

#include "fmtlog.h"

int main() 
{
  FMTLOG(fmtlog::INF, "The answer is {}.", 42);
}

giving 14:51:17.007652 source.cpp:8 INF[29545 ] The answer is 42. 🎉