FMT issues

[sab24]

Hi, I'm trying to evaluate whether to use spdlog in my project, but so far it has only complicated the workflow and not provided the intended benefits of a logging library. Including this project gives strange errors. I saw in the git history that {fmt} has updated their namespaces, but I still have a lot of errors in spdlog/fmt/bundled/format.h:

/home/cross/include/spdlog/fmt/bundled/format.h:308:30: error: use of undeclared identifier 'void_t'                                                                                 
struct iterator_category<It, void_t<typename It::iterator_category>> {                                                                                                               
                             ^                                                                                                                                                       
/home/cross/include/spdlog/fmt/bundled/format.h:503:51: error: unknown type name 'char8_type'; did you mean 'detail::char8_type'?                                                    
inline size_t count_code_points(basic_string_view<char8_type> s) {                                                                                                                   
                                                  ^~~~~~~~~~                                                                                                                         
                                                  detail::char8_type                                                                                                                 
/home/cross/include/fmt/core.h:328:7: note: 'detail::char8_type' declared here                                                                                                       
using char8_type = char8_t;                                                                                                                                                          
      ^                                                                                                                                                                              
                                                                                                            
In file included from /home/cross/include/spdlog/spdlog.h:12:                                                                                                                        
In file included from /home/cross/include/spdlog/common.h:36:                                                                                                                        
In file included from /home/cross/include/spdlog/fmt/fmt.h:21:                                                                                                                       
/home/cross/include/spdlog/fmt/bundled/format.h:515:50: error: unknown type name 'char8_type'; did you mean 'detail::char8_type'?                                                    
inline size_t code_point_index(basic_string_view<char8_type> s, size_t n) {                                                                                                          
                                                 ^~~~~~~~~~                                                                                                                          
                                                 detail::char8_type                                                                                                                  
/home/cross/include/fmt/core.h:328:7: note: 'detail::char8_type' declared here                                                                                                       
using char8_type = char8_t;                                                                                                                                                          
      ^                                                                                                                                                                              
                                                                                                              
In file included from /home/cross/include/spdlog/spdlog.h:12:                                                                                                                        
In file included from /home/cross/include/spdlog/common.h:36:                                                                                                                        
In file included from /home/cross/include/spdlog/fmt/fmt.h:21:                                                                                                                       
/home/cross/include/spdlog/fmt/bundled/format.h:516:9: error: unknown type name 'char8_type'; did you mean 'detail::char8_type'?                                                     
  const char8_type* data = s.data();                                                                                                                                                 
        ^~~~~~~~~~                                                                                                                                                                   
        detail::char8_type                                                                                                                                                           
/home/cross/include/fmt/core.h:328:7: note: 'detail::char8_type' declared here                                                                                                       
using char8_type = char8_t;                                                                                                                                                          
      ^                                                                                                                                                                              
                                                                                                             
In file included from /home/cross/include/spdlog/spdlog.h:12:                                                                                                                        
In file included from /home/cross/include/spdlog/common.h:36:                                                                                                                        
In file included from /home/cross/include/spdlog/fmt/fmt.h:21:                                                                                                                       
/home/cross/include/spdlog/fmt/bundled/format.h:526:8: error: unknown type name 'char8_type'; did you mean 'detail::char8_type'?                                                     
inline char8_type to_char8_t(char c) { return static_cast<char8_type>(c); }                                                                                                          
       ^~~~~~~~~~                                                                                                                                                                    
       detail::char8_type                                                                                                                                                            
/home/cross/include/fmt/core.h:328:7: note: 'detail::char8_type' declared here
using char8_type = char8_t;

In file included from /home/cross/include/spdlog/spdlog.h:12:
In file included from /home/cross/include/spdlog/common.h:36:
In file included from /home/cross/include/spdlog/fmt/fmt.h:21:
/home/cross/include/spdlog/fmt/bundled/format.h:526:59: error: unknown type name 'char8_type'; did you mean 'detail::char8_type'?
inline char8_type to_char8_t(char c) { return static_cast<char8_type>(c); }

[sab24]

Made it compile by replacing the core.h format.h and format-inl.h files from fmt library head

[tt4g]

This refers to the fmt library header, which is not bundled with spdlog: /home/cross/include/fmt/core.h:328:7: note: 'detail::char8_type' declared here

When using external fmt with spdlog, you have to define and build the CMake variable SPDLOG_FMT_EXTERNAL.
If use header-only fmt, define SPDLOG_FMT_EXTERNAL_HO instead of SPDLOG_FMT_EXTERNAL.

spdlog/CMakeLists.txt

Lines 86 to 92 in 616caa5

	option(SPDLOG_FMT_EXTERNAL "Use external fmt library instead of bundled" OFF)
	option(SPDLOG_FMT_EXTERNAL_HO "Use external fmt header-only library instead of bundled" OFF)
	option(SPDLOG_NO_EXCEPTIONS "Compile with -fno-exceptions. Call abort() on any spdlog exceptions" OFF)
	if(SPDLOG_FMT_EXTERNAL AND SPDLOG_FMT_EXTERNAL_HO)
	message(FATAL_ERROR "SPDLOG_FMT_EXTERNAL and SPDLOG_FMT_EXTERNAL_HO are mutually exclusive")
	endif()