1.5.1: FMT_STRING() breaks spdlog in Examples/ColourSpace/colourspace.cpp

[jfpanisset]

In 1.5.1 the calls to spdlog::info() wrap the string passed to spdlog in the FMT_STRING() macro.

On gcc 14.2.1 when spdlog() is called with a fstring-style string and variables, everything is fine:

spdlog::info(FMT_STRING("unknown colour management style '{}'"), style);

but when the string is a simple string without variable interpolation:

spdlog::info(FMT_STRING("Specifying preferred input colourspaces"));

the compiler rejects it, complaining about incomplete types.

I see this with spdlog 1.5.3 or 1.7.0, with either the corresponding fmt compiled separately, or using the one bundled in spdlog. Same issue if I patch CMakeLists.txt to force compiling in C++ 20 mode.

I am able to get around the issue with this gross patch:

// In some environments {fmt} needs FMT_STRING
//#ifndef FMT_STRING
#define FMT_STRING(x) x
//#endif

at the cost of gcc complaining about FMT_STRING being redifined.

I don't understand enough about spdlog, fmt or template metaprogramming to get at the root of the issue. I can provide more details on the errors reported by gcc if needed.

[garyo]

I don 't see this with any recent fmt/spdlog with gcc, but in semi-recent fmt (e.g. with spdlog 1.8+), FMT_STRING is no longer needed, so I'll just remove it.

[garyo]

PR merged. Closing.