Update add_module_library

CMakeLists.txt

@@ -56,22 +56,16 @@ function(add_module_library name)
     return()
   endif ()
 
-  # Check if modules are supported.
-  set(have_modules FALSE)
-  if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND
-      CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0)
-    set(have_modules TRUE)
-  endif ()
-  if (NOT have_modules)
-    message(FATAL_ERROR "Modules not supported.")
-  endif ()
-
   # Modules require C++20.
   target_compile_features(${name} PUBLIC cxx_std_20)
+  if (CMAKE_COMPILER_IS_GNUCXX)
+    target_compile_options(${name} PUBLIC -fmodules-ts)
+  endif ()
 
   # `std` is affected by CMake options and may be higher than C++20.
   get_target_property(std ${name} CXX_STANDARD)
 
+  if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     set(pcms)
     foreach (src ${sources})
       get_filename_component(pcm ${src} NAME_WE)
@@ -80,7 +74,8 @@ function(add_module_library name)
       # Propagate -fmodule-file=*.pcm to targets that link with this library.
       target_compile_options(${name} PUBLIC -fmodule-file=${pcm})
 
-    # Use an absolute path to prevent target_link_libraries prepending -l to it.
+      # Use an absolute path to prevent target_link_libraries prepending -l
+      # to it.
       set(pcms ${pcms} ${CMAKE_CURRENT_BINARY_DIR}/${pcm})
       add_custom_command(
         OUTPUT ${pcm}
@@ -94,19 +89,20 @@ function(add_module_library name)
     endforeach ()
 
     # Add .pcm files as sources to make sure they are built before the library.
-  set(files)
+    set(sources)
     foreach (pcm ${pcms})
       get_filename_component(pcm_we ${pcm} NAME_WE)
       set(obj ${pcm_we}.o)
       # Use an absolute path to prevent target_link_libraries prepending -l.
-    set(files ${files} ${pcm} ${CMAKE_CURRENT_BINARY_DIR}/${obj})
+      set(sources ${sources} ${pcm} ${CMAKE_CURRENT_BINARY_DIR}/${obj})
       add_custom_command(
         OUTPUT ${obj}
         COMMAND ${CMAKE_CXX_COMPILER} $<TARGET_PROPERTY:${name},COMPILE_OPTIONS>
                 -c -o ${obj} ${pcm}
         DEPENDS ${pcm})
     endforeach ()
-  target_sources(${name} PRIVATE ${files})  
+  endif ()
+  target_sources(${name} PRIVATE ${sources})
 endfunction()
 
 include(CMakeParseArguments)

src/fmt.cc

@@ -76,10 +76,6 @@ export module fmt;
 #include "fmt/printf.h"
 #include "fmt/xchar.h"
 
-#if !(defined(__cpp_modules) || FMT_CLANG_VERSION >= 1600)
-#  error modules not supported
-#endif
-
 // gcc doesn't yet implement private module fragments
 #if !FMT_GCC_VERSION
 module : private;