ostream.h does not have FMT_EXPORT

[maths644311798]

I use gcc 13 and cmake 3.27.0 to compile a project with standard C++20. It shows the following errors:

/usr/local/include/fmt/ostream.h:158:1: error: 'FMT_EXPORT' does not name a type
158 | FMT_EXPORT template
| ^~~~~~~~~~
/usr/local/include/fmt/ostream.h:177:1: error: 'FMT_EXPORT' does not name a type
177 | FMT_EXPORT template <typename... T>
| ^~~~~~~~~~
/usr/local/include/fmt/ostream.h:186:1: error: 'FMT_EXPORT' does not name a type
186 | FMT_EXPORT
| ^~~~~~~~~~
/usr/local/include/fmt/ostream.h:194:1: error: 'FMT_EXPORT' does not name a type
194 | FMT_EXPORT template <typename... T>
| ^~~~~~~~~~
/usr/local/include/fmt/ostream.h:199:1: error: 'FMT_EXPORT' does not name a type
199 | FMT_EXPORT

I know that FMT_EXPORT is in fmt.cc. But I don't know why the compiler can not find it. The linking sentence in CMakeLists.txt is

target_link_libraries(${PROJECT_NAME} fmt)

It seems that this problem comes with another library spdlog. See gabime/spdlog#2872 (comment)

[vitaut]

FMT_EXPORT is defined here:

fmt/include/fmt/core.h

Line 183 in e8259c5

# define FMT_EXPORT

Most likely you are including incompatible versions of {fmt} headers (part from spdlog and part from elsewhere).