remove useless flags to build modules on clang

1 files changed, 18 insertions, 19 deletions

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 763cfb6cd..54be2c80f 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -116,22 +116,16 @@ end
 
 -- load module support for the current target
 function load(target)
-    local modulesflag, modulestsflag = get_modulesflag(target)
-    local builtinmodulemapflag = get_builtinmodulemapflag(target)
-    local implicitmodulesflag = get_implicitmodulesflag(target)
-    local noimplicitmodulemapsflag = get_noimplicitmodulemapsflag(target)
+    local clangmodulesflag, modulestsflag, withoutflag = get_modulesflag(target)
 
     -- add module flags
-    target:add("cxxflags", modulesflag)
-    if not modulesflag then
+    if not withoutflag then
         target:add("cxxflags", modulestsflag)
     end
 
+    -- enable clang modules to emulate std modules
     if target:policy("build.c++.clang.stdmodules") then
-       target:add("cxxflags", builtinmodulemapflag, {force = true})
-       target:add("cxxflags", implicitmodulesflag, {force = true})
-    else
-       target:add("cxxflags", noimplicitmodulemapsflag, {force = true})
+       target:add("cxxflags", clangmodulesflag)
     end
 
     -- fix default visibility for functions and variables [-fvisibility] differs in PCH file vs. current file
@@ -698,21 +692,25 @@ function get_bmi_extension()
 end
 
 function get_modulesflag(target)
-    local modulesflag = _g.modulesflag
+    local clangmodulesflag = _g.clangmodulesflag
     local modulestsflag = _g.modulestsflag
-    if modulesflag == nil and modulestsflag == nil then
+    local withoutflag = _g.withoutflag
+    if clangmodulesflag == nil and modulestsflag == nil then
         local compinst = target:compiler("cxx")
         if compinst:has_flags("-fmodules", "cxxflags", {flagskey = "clang_modules"}) then
-            modulesflag = "-fmodules"
+            clangmodulesflag = "-fmodules"
         end
         if compinst:has_flags("-fmodules-ts", "cxxflags", {flagskey = "clang_modules_ts"}) then
             modulestsflag = "-fmodules-ts"
         end
-        assert(modulesflag or modulestsflag, "compiler(clang): does not support c++ module!")
-        _g.modulesflag = modulesflag or false
+        local clang_version = _get_clang_version(target)
+        withoutflag = semver.compare(clang_version, "16.0") >= 0
+        assert(withoutflag or modulestsflag, "compiler(clang): does not support c++ module!")
+        _g.clangmodulesflag = clangmodulesflag or false
         _g.modulestsflag = modulestsflag or false
+        _g.withoutflag = withoutflag or false
     end
-    return modulesflag or nil, modulestsflag or nil
+    return clangmodulesflag or nil, modulestsflag or nil, withoutflag or nil
 end
 
 function get_builtinmodulemapflag(target)
@@ -814,9 +812,10 @@ function has_headerunitsupport(target)
     local support_headerunits = _g.support_headerunits
     if support_headerunits == nil then
         local compinst = target:compiler("cxx")
-        local modulesflag, modulestsflag = get_modulesflag(target)
-        if compinst:has_flags(modulesflag or modulestsflag .. " -std=c++20 -x c++-user-header", "cxxflags", {flagskey = "clang_user_header_unit_support", tryrun = true}) and
-           compinst:has_flags(modulesflag or modulestsflag .. " -std=c++20 -x c++-system-header", "cxxflags", {flagskey = "clang_system_header_unit_support", tryrun = true}) then
+        local _, modulestsflag, withoutflag = get_modulesflag(target)
+        modulestsflag = withoutflag and "" or modulestsflag
+        if compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-user-header", "cxxflags", {flagskey = "clang_user_header_unit_support", tryrun = true}) and
+           compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-system-header", "cxxflags", {flagskey = "clang_system_header_unit_support", tryrun = true}) then
             support_headerunits = true
         end
         _g.support_headerunits = support_headerunits or false