From 0936ad49411c55cf4130793750336e011366ebbf Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Tue, 14 Feb 2023 00:07:38 +0800
Subject: improve clang for stdmodules

---
 .../modules/detect/tools/find_clang_scan_deps.lua  | 55 ++++++++++++++++
 xmake/rules/c++/modules/modules_support/clang.lua  | 76 +++++++++++++++++-----
 xmake/rules/c++/modules/modules_support/common.lua |  2 +-
 3 files changed, 116 insertions(+), 17 deletions(-)
 create mode 100644 xmake/modules/detect/tools/find_clang_scan_deps.lua

diff --git a/xmake/modules/detect/tools/find_clang_scan_deps.lua b/xmake/modules/detect/tools/find_clang_scan_deps.lua
new file mode 100644
index 000000000..f4b9cd87b
--- /dev/null
+++ b/xmake/modules/detect/tools/find_clang_scan_deps.lua
@@ -0,0 +1,55 @@
+--!A cross-platform build utility based on Lua
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+--
+-- Copyright (C) 2015-present, TBOOX Open Source Group.
+--
+-- @author      ruki
+-- @file        find_clang_scan_deps.lua
+--
+
+-- imports
+import("lib.detect.find_program")
+import("lib.detect.find_programver")
+
+-- find clang-scan-deps
+--
+-- @param opt   the argument options, e.g. {version = true}
+--
+-- @return      program, version
+--
+-- @code
+--
+-- local clang_scan_deps = find_clang_scan_deps()
+-- local clang_scan_deps, version = find_clang_scan_deps({program = "clang-scan-deps", version = true})
+--
+-- @endcode
+--
+function main(opt)
+    opt = opt or {}
+    local program = find_program(opt.program or "clang-scan-deps", opt)
+    if not program and is_host("macosx") then
+        local llvm = try {function () return os.iorunv("brew", {"--prefix", "llvm"}) end}
+        if llvm then
+            opt.paths = opt.paths or {}
+            opt.force = true
+            table.insert(opt.paths, path.join(llvm:trim(), "bin"))
+            program = find_program(opt.program or "clang-scan-deps", opt)
+        end
+    end
+    local version = nil
+    if program and opt and opt.version then
+        version = find_programver(program, opt)
+    end
+    return program, version
+end
diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 1078c4176..763cfb6cd 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -32,6 +32,47 @@ import("private.action.build.object", {alias = "objectbuilder"})
 import("common")
 import("stl_headers")
 
+-- get clang version
+function _get_clang_version(target)
+    local clang_version = _g.clang_version
+    if not clang_version then
+        local program, toolname = target:tool("cxx")
+        if program and (toolname == "clang" or toolname == "clangxx") then
+            local clang = find_tool("clang", {program = program, version = true})
+            if clang then
+                clang_version = clang.version
+            end
+        end
+        clang_version = clang_version or false
+        _g.clang_version = clang_version
+    end
+    return clang_version or nil
+end
+
+-- get clang-scan-deps
+function _get_clang_scan_deps(target)
+    local clang_scan_deps = _g.clang_scan_deps
+    if not clang_scan_deps then
+        local program, toolname = target:tool("cxx")
+        if program and (toolname == "clang" or toolname == "clangxx") then
+            local dir = path.directory(program)
+            local basename = path.basename(program)
+            local extension = path.extension(program)
+            program = (basename:gsub("clang", "clang-scan-deps")) .. extension
+            if os.isdir(dir) then
+                program = path.join(dir, program)
+            end
+            local result = find_tool("clang-scan-deps", {program = program, version = true})
+            if result then
+                clang_scan_deps = result.program
+            end
+        end
+        clang_scan_deps = clang_scan_deps or false
+        _g.clang_scan_deps = clang_scan_deps
+    end
+    return clang_scan_deps or nil
+end
+
 -- add a module or an header unit into the mapper
 --
 -- e.g
@@ -82,7 +123,7 @@ function load(target)
 
     -- add module flags
     target:add("cxxflags", modulesflag)
-    if not modulesflag or target:is_plat("macosx") then
+    if not modulesflag then
         target:add("cxxflags", modulestsflag)
     end
 
@@ -257,13 +298,13 @@ function generate_dependencies(target, sourcebatch, opt)
             local outputdir = common.get_outputdir(target, sourcefile)
             local jsonfile = path.translate(path.join(outputdir, path.filename(sourcefile) .. ".json"))
             if has_clangscandepssupport(target) and not target:policy("build.c++.clang.fallbackscanner") then
-                local clangscandeps = find_tool("clang-scan-deps")
+                local clangscandeps = _get_clang_scan_deps(target)
                 local compinst = target:compiler("cxx")
                 local compflags = compinst:compflags({sourcefile = file, target = target})
                 local flags = table.join({"--format=p1689", "--", compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile)}, compflags)
 
-                vprint(table.concat(table.join(clangscandeps.program, flags), " "))
-                local outdata, errdata = os.iorunv(clangscandeps.program, flags)
+                vprint(table.concat(table.join(clangscandeps, flags), " "))
+                local outdata, errdata = os.iorunv(clangscandeps, flags)
                 assert(errdata, errdata)
 
                 io.writefile(jsonfile, outdata)
@@ -301,13 +342,15 @@ function generate_dependencies(target, sourcebatch, opt)
                             break
                         end
                     end
+                    if has_std_modules then
 
-                    assert(not (has_std_modules and not target:policy("build.c++.clang.stdmodules")),
-                           [[On llvm <= 16 standard C++ modules are not supported ;
-                           they can be emulated through clang modules and supported only on libc++ ;
-                           please add -stdlib=libc++ cxx flag or disable strict mode]])
+                        -- we need clang >= 17.0 or use clang stdmodules if the current target contains std module
+                        local clang_version = _get_clang_version(target)
+                        assert((clang_version and semver.compare(clang_version, "17.0") >= 0) or target:policy("build.c++.clang.stdmodules"),
+                               [[On llvm <= 16 standard C++ modules are not supported ;
+                               they can be emulated through clang modules and supported only on libc++ ;
+                               please add -stdlib=libc++ cxx flag or disable strict mode]])
 
-                    if has_std_modules then
                         target:data_set("cxx.modules.use_libc++", true)
                         if target:data("cxx.modules.use_libc++") then
                             _enable_libcxx(target)
@@ -771,9 +814,9 @@ function has_headerunitsupport(target)
     local support_headerunits = _g.support_headerunits
     if support_headerunits == nil then
         local compinst = target:compiler("cxx")
-        local modulesflag, moduletsflag = get_modulesflag(target)
-        if compinst:has_flags(modulesflag or moduletsflag .. " -std=c++20 -x c++-user-header", "cxxflags", {flagskey = "clang_user_header_unit_support", tryrun = true}) and
-           compinst:has_flags(modulesflag or moduletsflag .. " -std=c++20 -x c++-system-header", "cxxflags", {flagskey = "clang_system_header_unit_support", tryrun = true}) then
+        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
             support_headerunits = true
         end
         _g.support_headerunits = support_headerunits or false
@@ -784,8 +827,9 @@ end
 function has_clangscandepssupport(target)
     local support_clangscandeps = _g.support_clangscandeps
     if support_clangscandeps == nil then
-        local clangscandeps = find_tool("clang-scan-deps", {version = true})
-        if clangscandeps and clangscandeps.version and semver.compare(clangscandeps.version, "16.0") >= 0 then
+        local clangscandeps = _get_clang_scan_deps(target)
+        local clang_version = _get_clang_version(target)
+        if clangscandeps and clang_version and semver.compare(clang_version, "16.0") >= 0 then
             support_clangscandeps = true
         end
         _g.support_clangscandeps = support_clangscandeps or false
@@ -797,8 +841,8 @@ function get_moduleoutputflag(target)
     local moduleoutputflag = _g.moduleoutputflag
     if moduleoutputflag == nil then
         local compinst = target:compiler("cxx")
-        local clang = find_tool("clang", {version = true})
-        if compinst:has_flags("-fmodule-output=", "cxxflags", {flagskey = "clang_module_output", tryrun = true}) and semver.compare(clang.version, "16.0") >= 0 then
+        local clang_version = _get_clang_version(target)
+        if compinst:has_flags("-fmodule-output=", "cxxflags", {flagskey = "clang_module_output", tryrun = true}) and semver.compare(clang_version, "16.0") >= 0 then
             moduleoutputflag = "-fmodule-output="
         end
         _g.moduleoutputflag = moduleoutputflag or false
diff --git a/xmake/rules/c++/modules/modules_support/common.lua b/xmake/rules/c++/modules/modules_support/common.lua
index 7a43cd5f2..8996d0ddf 100644
--- a/xmake/rules/c++/modules/modules_support/common.lua
+++ b/xmake/rules/c++/modules/modules_support/common.lua
@@ -740,4 +740,4 @@ function get_outputdir(target, module)
         end
         return moduledir
     end
-end
\ No newline at end of file
+end
-- 
cgit v1.3.1


From e288951c41b72f3ccf3cfed495417fea7dee1e79 Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Wed, 15 Feb 2023 22:46:13 +0800
Subject: add snippet to has_flags

---
 xmake/modules/detect/tools/cl/has_flags.lua   | 6 +++---
 xmake/modules/detect/tools/gcc/has_flags.lua  | 5 +++--
 xmake/modules/detect/tools/nvcc/has_flags.lua | 6 +++---
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/xmake/modules/detect/tools/cl/has_flags.lua b/xmake/modules/detect/tools/cl/has_flags.lua
index fe57e38b0..e1e986303 100644
--- a/xmake/modules/detect/tools/cl/has_flags.lua
+++ b/xmake/modules/detect/tools/cl/has_flags.lua
@@ -54,10 +54,10 @@ end
 function _check_try_running(flags, opt)
 
     -- make an stub source file
-    local tmpdir = path.join(os.tmpdir(), "detect")
-    local sourcefile = path.join(tmpdir, "cl_has_flags" .. _get_extension(opt))
+    local snippet = opt.snippet or "int main(int argc, char** argv)\n{return 0;}"
+    local sourcefile = os.tmpfile("cl_has_flags:" .. snippet) .. _get_extension(opt)
     if not os.isfile(sourcefile) then
-        io.writefile(sourcefile, "int main(int argc, char** argv)\n{return 0;}")
+        io.writefile(sourcefile, snippet)
     end
 
     -- check it
diff --git a/xmake/modules/detect/tools/gcc/has_flags.lua b/xmake/modules/detect/tools/gcc/has_flags.lua
index 64fa70df8..6ab7ce810 100644
--- a/xmake/modules/detect/tools/gcc/has_flags.lua
+++ b/xmake/modules/detect/tools/gcc/has_flags.lua
@@ -77,9 +77,10 @@ end
 function _check_try_running(flags, opt, islinker)
 
     -- make an stub source file
-    local sourcefile = path.join(os.tmpdir(), "detect", "gcc_has_flags" .. _get_extension(opt))
+    local snippet = opt.snippet or "int main(int argc, char** argv)\n{return 0;}"
+    local sourcefile = os.tmpfile("gcc_has_flags:" .. snippet) .. _get_extension(opt)
     if not os.isfile(sourcefile) then
-        io.writefile(sourcefile, "int main(int argc, char** argv)\n{return 0;}")
+        io.writefile(sourcefile, snippet)
     end
 
     -- check flags for linker
diff --git a/xmake/modules/detect/tools/nvcc/has_flags.lua b/xmake/modules/detect/tools/nvcc/has_flags.lua
index d96ffdfe8..c75f6e114 100644
--- a/xmake/modules/detect/tools/nvcc/has_flags.lua
+++ b/xmake/modules/detect/tools/nvcc/has_flags.lua
@@ -101,13 +101,13 @@ end
 function _check_try_running(flags, opt, islinker)
 
     -- make an stub source file
-    local sourcefile = path.join(os.tmpdir(), "detect", "nvcc_has_flags.cu")
+    local snippet = opt.snippet or "int main(int argc, char** argv)\n{return 0;}"
+    local sourcefile = os.tmpfile("nvcc_has_flags:" .. snippet) .. ".cu"
     if not os.isfile(sourcefile) then
-        io.writefile(sourcefile, "int main(int argc, char** argv)\n{return 0;}")
+        io.writefile(sourcefile, snippet)
     end
 
     local args = table.join("-o", os.nuldev(), sourcefile)
-
     if not islinker then
         table.insert(args, 1, "-c")
     end
-- 
cgit v1.3.1


From 3cdbc4183fe807d2bf4bbcb19aef1f85e33c1d6d Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Tue, 14 Feb 2023 18:45:42 +0100
Subject: remove useless flags to build modules on clang

---
 xmake/rules/c++/modules/modules_support/clang.lua | 37 +++++++++++------------
 1 file 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
-- 
cgit v1.3.1


From 3dff84c9e8fe939d1ed29123797060db56925e26 Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:14:02 +0100
Subject: fix compilation of non .cpp private module with clang

---
 xmake/rules/c++/modules/modules_support/clang.lua | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 54be2c80f..3a7ad13b9 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -230,6 +230,8 @@ function _build_modulefile(target, sourcefile, opt)
         else
             bmiflags = table.join("-x", "c++-module", "--precompile", compflags, common_args, requiresflags)
         end
+    else
+        compileflags = {"-x", "c++"}
     end
 
     if bmiflags then
-- 
cgit v1.3.1


From 51fad68409dc0ac9c70702397d0d344ca0aaf3f9 Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:14:15 +0100
Subject: fix libc++ link

---
 xmake/rules/c++/modules/modules_support/clang.lua | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 3a7ad13b9..06425ff40 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -111,7 +111,8 @@ end
 -- enable libc++
 function _enable_libcxx(target)
     target:add("cxxflags", "-stdlib=libc++")
-    target:add("syslinks", "c++")
+    target:add("ldflags", "-stdlib=libc++")
+    target:add("shflags", "-stdlib=libc++")
 end
 
 -- load module support for the current target
-- 
cgit v1.3.1


From 475734e6f4a27a3e3f2cdab3d3a93a5e949b7b0e Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:15:06 +0100
Subject: use -fmodule-file=<name>=<bmi> for named module on clang

---
 xmake/rules/c++/modules/modules_support/clang.lua | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 06425ff40..df3cd066b 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -79,15 +79,21 @@ end
 -- -fmodule-file=build/.gens/Foo/rules/modules/cache/foo.pcm
 -- -fmodule-file=build/.gens/Foo/rules/modules/cache/iostream.pcm
 -- -fmodule-file=build/.gens/Foo/rules/modules/cache/bar.hpp.pcm
+-- on LLVM >= 16
+-- -fmodule-file=foo=build/.gens/Foo/rules/modules/cache/foo.pcm
+-- -fmodule-file=build/.gens/Foo/rules/modules/cache/iostream.pcm
+-- -fmodule-file=build/.gens/Foo/rules/modules/cache/bar.hpp.pcm
 --
-function _add_module_to_mapper(target, name, bmifile, deps)
+function _add_module_to_mapper(target, name, bmifile, deps, namedmodule)
     local modulemap = _get_modulemap_from_mapper(target, name)
     if modulemap then
         return
     end
 
+    local clang_version = _get_clang_version(target)
+    namedmodule = namedmodule and semver.compare(clang_version, "16.0") >= 0
     local modulefileflag = get_modulefileflag(target)
-    local mapflag = modulefileflag .. bmifile
+    local mapflag = namedmodule and format("%s%s=%s", modulefileflag, name, bmifile) or modulefileflag .. bmifile
     modulemap = {flag = mapflag, deps = deps}
     common.localcache():set2(_mapper_cachekey(target), "modulemap" .. name, modulemap)
 end
@@ -596,7 +602,7 @@ function build_modules_for_batchjobs(target, batchjobs, objectfiles, modules, op
                         target:add("objectfiles", objectfile)
 
                         if provide then
-                            _add_module_to_mapper(target, name, bmifile, requiresflags)
+                            _add_module_to_mapper(target, name, bmifile, requiresflags, true)
                         end
                     elseif requiresflags then
                         local cxxflags = {}
@@ -658,7 +664,7 @@ function build_modules_for_batchcmds(target, batchcmds, objectfiles, modules, op
                 if provide then
                     _batchcmds_compile(batchcmds, target, table.join(flags,
                         {"-x", "c++-module", "--precompile", "-c", path(cppfile), "-o", path(provide.bmi)}))
-                    _add_module_to_mapper(target, name, provide.bmi)
+                    _add_module_to_mapper(target, name, provide.bmi, nil, true)
                 end
                 _batchcmds_compile(batchcmds, target, file, table.join(flags,
                     not provide and {"-x", "c++"} or {}, {"-c", file, "-o", path(objectfile)}))
-- 
cgit v1.3.1


From 4220ee54e0f12461ef2186f8ccf4a7823ece2ee7 Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:15:27 +0100
Subject: fix libc++ detection

---
 xmake/rules/c++/modules/modules_support/clang.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index df3cd066b..e8d52dcba 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -157,7 +157,7 @@ function load(target)
     -- on ubuntu:
     -- sudo apt install libc++-dev libc++abi-15-dev
     --
-    local flags = table.join(target:get("cxxflags"), get_config("cxxflags") or {})
+    local flags = table.join(target:get("cxxflags") or {}, get_config("cxxflags") or {})
     target:data_set("cxx.modules.use_libc++", table.contains(flags, "-stdlib=libc++", "clang::-stdlib=libc++"))
     if target:data("cxx.modules.use_libc++") then
         _enable_libcxx(target)
-- 
cgit v1.3.1


From f6b9179af9ff16461e023f00ef10535b6e575ced Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:15:42 +0100
Subject: fix headerunit clang support detection

---
 xmake/rules/c++/modules/modules_support/clang.lua | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index e8d52dcba..d505d779c 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -823,8 +823,8 @@ function has_headerunitsupport(target)
         local compinst = target:compiler("cxx")
         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
+        if compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-user-header", "cxxflags", {snippet = "inline int foo() { return 0; }", flagskey = "clang_user_header_unit_support", tryrun = true}) and
+           compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-system-header", "cxxflags", {snippet = "inline int foo() { return 0; }", flagskey = "clang_system_header_unit_support", tryrun = true}) then
             support_headerunits = true
         end
         _g.support_headerunits = support_headerunits or false
-- 
cgit v1.3.1


From 0765350a8935fe493e0846543081dc29463ea953 Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:29:10 +0100
Subject: fix clang module vprint

---
 xmake/rules/c++/modules/modules_support/clang.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index d505d779c..3d45fd43f 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -246,7 +246,7 @@ function _build_modulefile(target, sourcefile, opt)
     end
 
     compileflags = table.join2(compileflags, compflags, common_args, requiresflags or {})
-    vprint(compinst:compcmd(bmifile or sourcefile, objectfile, {compflags = compileflags, rawargs = true}))
+    vprint(compinst:compcmd(bmiflags and bmifile or sourcefile, objectfile, {compflags = compileflags, rawargs = true}))
 
     if not dryrun then
 
-- 
cgit v1.3.1


From 46e033b7beaba56ed7dba4587ab98992b1d9f646 Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 18:57:29 +0100
Subject: fix compflags for clang-scan module dependencies scan

---
 xmake/rules/c++/modules/modules_support/clang.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 3d45fd43f..40c91981e 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -303,7 +303,7 @@ function generate_dependencies(target, sourcebatch, opt)
             if has_clangscandepssupport(target) and not target:policy("build.c++.clang.fallbackscanner") then
                 local clangscandeps = _get_clang_scan_deps(target)
                 local compinst = target:compiler("cxx")
-                local compflags = compinst:compflags({sourcefile = file, target = target})
+                local compflags = compinst:compflags({sourcefile = sourcefile, target = target})
                 local flags = table.join({"--format=p1689", "--", compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile)}, compflags)
 
                 vprint(table.concat(table.join(clangscandeps, flags), " "))
-- 
cgit v1.3.1


From d39fdee559df35b35c03ba616558f5614b126a9b Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Wed, 15 Feb 2023 19:04:13 +0100
Subject: remove clang module flags deduplication

---
 xmake/rules/c++/modules/modules_support/clang.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 40c91981e..9d5911775 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -233,7 +233,7 @@ function _build_modulefile(target, sourcefile, opt)
         bmifile = opt.provide.bmifile
 
         if moduleoutputflag then
-            compileflags = table.join("-x", "c++-module", moduleoutputflag .. bmifile, compflags, common_args, requiresflags)
+            compileflags = table.join("-x", "c++-module", moduleoutputflag .. bmifile, requiresflags)
         else
             bmiflags = table.join("-x", "c++-module", "--precompile", compflags, common_args, requiresflags)
         end
-- 
cgit v1.3.1


From 32f6a7942a263bfb60ea39f2a48bd75a441109ec Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 08:09:17 +0800
Subject: fix tests

---
 tests/projects/package/depconfigs/xmake.lua | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/tests/projects/package/depconfigs/xmake.lua b/tests/projects/package/depconfigs/xmake.lua
index 2559ced03..377c8899b 100644
--- a/tests/projects/package/depconfigs/xmake.lua
+++ b/tests/projects/package/depconfigs/xmake.lua
@@ -1,11 +1,8 @@
 add_requires("libpng", {system = false, configs = {vs_runtime = "MD"}})
 add_requires("libtiff", {system = false, configs = {vs_runtime = "MD", zlib = true}})
-add_requires("libwebp")
 
-add_requireconfs("libwebp",            {system = false, configs = {shared = true, vs_runtime = "MD"}})
 add_requireconfs("libpng.zlib",        {system = false, override = true, configs = {cxflags = "-DTEST1"}, version = "1.2.10"})
 add_requireconfs("libtiff.*|cmake",    {system = false, configs = {cxflags = "-DTEST2"}})
-add_requireconfs("libwebp.**|cmake",   {system = false, configs = {cxflags = "-DTEST3"}})
 
 target("test")
     set_kind("binary")
@@ -39,18 +36,3 @@ target("test2")
         end
     end)
 
-target("test3")
-    set_kind("binary")
-    add_files("src/*.c")
-    add_packages("libwebp")
-    before_build(function (target)
-        if target:pkg("libwebp") then
-            local found
-            for _, linkdir in ipairs(target:pkg("libwebp"):get("linkdirs")) do
-                if linkdir:find("zlib", 1, true) then
-                    found = true
-                end
-            end
-            assert(found, "package(zlib) not found!")
-        end
-    end)
-- 
cgit v1.3.1


From 3761c27bb3fa4ee92f73662e1bb9979fcc83f87a Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 22:32:42 +0800
Subject: format code

---
 xmake/rules/c++/modules/modules_support/clang.lua | 24 +++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 9d5911775..6766fae1a 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -84,17 +84,18 @@ end
 -- -fmodule-file=build/.gens/Foo/rules/modules/cache/iostream.pcm
 -- -fmodule-file=build/.gens/Foo/rules/modules/cache/bar.hpp.pcm
 --
-function _add_module_to_mapper(target, name, bmifile, deps, namedmodule)
+function _add_module_to_mapper(target, name, bmifile, opt)
+    opt = opt or {}
     local modulemap = _get_modulemap_from_mapper(target, name)
     if modulemap then
         return
     end
 
     local clang_version = _get_clang_version(target)
-    namedmodule = namedmodule and semver.compare(clang_version, "16.0") >= 0
+    local namedmodule = opt.namedmodule and semver.compare(clang_version, "16.0") >= 0
     local modulefileflag = get_modulefileflag(target)
     local mapflag = namedmodule and format("%s%s=%s", modulefileflag, name, bmifile) or modulefileflag .. bmifile
-    modulemap = {flag = mapflag, deps = deps}
+    modulemap = {flag = mapflag, deps = opt.deps}
     common.localcache():set2(_mapper_cachekey(target), "modulemap" .. name, modulemap)
 end
 
@@ -602,7 +603,7 @@ function build_modules_for_batchjobs(target, batchjobs, objectfiles, modules, op
                         target:add("objectfiles", objectfile)
 
                         if provide then
-                            _add_module_to_mapper(target, name, bmifile, requiresflags, true)
+                            _add_module_to_mapper(target, name, bmifile, {deps = requiresflags, namedmodule = true})
                         end
                     elseif requiresflags then
                         local cxxflags = {}
@@ -664,7 +665,7 @@ function build_modules_for_batchcmds(target, batchcmds, objectfiles, modules, op
                 if provide then
                     _batchcmds_compile(batchcmds, target, table.join(flags,
                         {"-x", "c++-module", "--precompile", "-c", path(cppfile), "-o", path(provide.bmi)}))
-                    _add_module_to_mapper(target, name, provide.bmi, nil, true)
+                    _add_module_to_mapper(target, name, provide.bmi, {namedmodule = true})
                 end
                 _batchcmds_compile(batchcmds, target, file, table.join(flags,
                     not provide and {"-x", "c++"} or {}, {"-c", file, "-o", path(objectfile)}))
@@ -823,8 +824,14 @@ function has_headerunitsupport(target)
         local compinst = target:compiler("cxx")
         local _, modulestsflag, withoutflag = get_modulesflag(target)
         modulestsflag = withoutflag and "" or modulestsflag
-        if compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-user-header", "cxxflags", {snippet = "inline int foo() { return 0; }", flagskey = "clang_user_header_unit_support", tryrun = true}) and
-           compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-system-header", "cxxflags", {snippet = "inline int foo() { return 0; }", flagskey = "clang_system_header_unit_support", tryrun = true}) then
+        if compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-user-header", "cxxflags", {
+                snippet = "inline int foo() { return 0; }",
+                flagskey = "clang_user_header_unit_support",
+                tryrun = true}) and
+           compinst:has_flags(modulestsflag .. " -std=c++20 -x c++-system-header", "cxxflags", {
+                snippet = "inline int foo() { return 0; }",
+                flagskey = "clang_system_header_unit_support",
+                tryrun = true}) then
             support_headerunits = true
         end
         _g.support_headerunits = support_headerunits or false
@@ -850,7 +857,8 @@ function get_moduleoutputflag(target)
     if moduleoutputflag == nil then
         local compinst = target:compiler("cxx")
         local clang_version = _get_clang_version(target)
-        if compinst:has_flags("-fmodule-output=", "cxxflags", {flagskey = "clang_module_output", tryrun = true}) and semver.compare(clang_version, "16.0") >= 0 then
+        if compinst:has_flags("-fmodule-output=", "cxxflags", {flagskey = "clang_module_output", tryrun = true}) and
+            semver.compare(clang_version, "16.0") >= 0 then
             moduleoutputflag = "-fmodule-output="
         end
         _g.moduleoutputflag = moduleoutputflag or false
-- 
cgit v1.3.1


From 44053082b5aa4765d9b6a10322a1ad8fc253a762 Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 23:30:58 +0800
Subject: fix visibility differs

---
 xmake/rules/c++/modules/modules_support/clang.lua | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 6766fae1a..71127da77 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -139,17 +139,19 @@ function load(target)
     -- fix default visibility for functions and variables [-fvisibility] differs in PCH file vs. current file
     -- module.pcm cannot be loaded due to a configuration mismatch with the current compilation.
     --
-    -- it will happen in binary target depend ont shared target with modules, and enable release mode at same time.
+    -- it will happen in binary target depend on library target with modules, and enable release mode at same time.
+    --
+    -- @see https://github.com/xmake-io/xmake/issues/3358#issuecomment-1432586767
     local dep_symbols
-    local has_shared_deps = false
+    local has_library_deps = false
     for _, dep in ipairs(target:orderdeps()) do
-        if dep:is_shared() then
+        if dep:is_shared() or dep:is_static() or dep:is_object() then
             dep_symbols = dep:get("symbols")
-            has_shared_deps = true
+            has_library_deps = true
             break
         end
     end
-    if has_shared_deps then
+    if has_library_deps then
         target:set("symbols", dep_symbols and dep_symbols or "none")
     end
 
-- 
cgit v1.3.1


From a7dea61c3953b96ef3335f0cac64b7bc2634bc03 Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 23:41:48 +0800
Subject: improve stdlib for clang

---
 xmake/rules/c++/modules/modules_support/clang.lua | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 71127da77..6c538373b 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -234,7 +234,6 @@ function _build_modulefile(target, sourcefile, opt)
     local bmiflags
     if opt.provide then
         bmifile = opt.provide.bmifile
-
         if moduleoutputflag then
             compileflags = table.join("-x", "c++-module", moduleoutputflag .. bmifile, requiresflags)
         else
@@ -244,6 +243,16 @@ function _build_modulefile(target, sourcefile, opt)
         compileflags = {"-x", "c++"}
     end
 
+    -- we can also enable libc++ when building modules
+    --
+    -- @see https://github.com/xmake-io/xmake/issues/3373
+    if target:data("cxx.modules.use_libc++") then
+        if bmiflags then
+            table.insert(bmiflags, "-stdlib=libc++")
+        end
+        table.insert(compileflags, "-stdlib=libc++")
+    end
+
     if bmiflags then
         vprint(compinst:compcmd(sourcefile, bmifile, {compflags = bmiflags, rawargs = true}))
     end
@@ -307,8 +316,13 @@ function generate_dependencies(target, sourcebatch, opt)
                 local clangscandeps = _get_clang_scan_deps(target)
                 local compinst = target:compiler("cxx")
                 local compflags = compinst:compflags({sourcefile = sourcefile, target = target})
-                local flags = table.join({"--format=p1689", "--", compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile)}, compflags)
-
+                local flags = table.join("--format=p1689", "--",
+                                         compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile),
+                                         compflags)
+                -- we can also enable libc++ when scaning deps
+                if target:data("cxx.modules.use_libc++") then
+                    table.insert(flags, "-stdlib=libc++")
+                end
                 vprint(table.concat(table.join(clangscandeps, flags), " "))
                 local outdata, errdata = os.iorunv(clangscandeps, flags)
                 assert(errdata, errdata)
-- 
cgit v1.3.1


From 9e8183b512ccf2bd2d9a14c9ca1caaabb3fdc2ef Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 23:43:06 +0800
Subject: improve scan std modules

---
 xmake/rules/c++/modules/modules_support/clang.lua | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 6c538373b..86ec44e9e 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -243,16 +243,6 @@ function _build_modulefile(target, sourcefile, opt)
         compileflags = {"-x", "c++"}
     end
 
-    -- we can also enable libc++ when building modules
-    --
-    -- @see https://github.com/xmake-io/xmake/issues/3373
-    if target:data("cxx.modules.use_libc++") then
-        if bmiflags then
-            table.insert(bmiflags, "-stdlib=libc++")
-        end
-        table.insert(compileflags, "-stdlib=libc++")
-    end
-
     if bmiflags then
         vprint(compinst:compcmd(sourcefile, bmifile, {compflags = bmiflags, rawargs = true}))
     end
@@ -319,7 +309,6 @@ function generate_dependencies(target, sourcebatch, opt)
                 local flags = table.join("--format=p1689", "--",
                                          compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile),
                                          compflags)
-                -- we can also enable libc++ when scaning deps
                 if target:data("cxx.modules.use_libc++") then
                     table.insert(flags, "-stdlib=libc++")
                 end
@@ -352,7 +341,10 @@ function generate_dependencies(target, sourcebatch, opt)
                     local has_std_modules = false
                     for _, r in ipairs(dependinfo.rules) do
                         for _, required in ipairs(r.requires) do
-                            if required["logical-name"] == "std" or required["logical-name"] == "std.compat" then
+                            -- it may be `std:utility`, ..
+                            -- @see https://github.com/xmake-io/xmake/issues/3373
+                            local logical_name = required["logical-name"]
+                            if logical_name and (logical_name == "std" or logical_name:startswith("std.") or logical_name:startswith("std:")) then
                                 has_std_modules = true
                                 break
                             end
-- 
cgit v1.3.1


From e76a80fe2b54d04c555529127496e0912cd83a09 Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 23:43:42 +0800
Subject: improve scandeps

---
 xmake/rules/c++/modules/modules_support/clang.lua | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 86ec44e9e..5adeba4fa 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -308,10 +308,8 @@ function generate_dependencies(target, sourcebatch, opt)
                 local compflags = compinst:compflags({sourcefile = sourcefile, target = target})
                 local flags = table.join("--format=p1689", "--",
                                          compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile),
+                                         "-stdlib=libc++",
                                          compflags)
-                if target:data("cxx.modules.use_libc++") then
-                    table.insert(flags, "-stdlib=libc++")
-                end
                 vprint(table.concat(table.join(clangscandeps, flags), " "))
                 local outdata, errdata = os.iorunv(clangscandeps, flags)
                 assert(errdata, errdata)
-- 
cgit v1.3.1


From 4b32e484b54f61f649e46a94823f99ee940c9ed3 Mon Sep 17 00:00:00 2001
From: ruki <waruqi@gmail.com>
Date: Thu, 16 Feb 2023 23:59:53 +0800
Subject: improve stdlib

---
 xmake/rules/c++/modules/modules_support/clang.lua | 42 ++++++++++++++---------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/xmake/rules/c++/modules/modules_support/clang.lua b/xmake/rules/c++/modules/modules_support/clang.lua
index 5adeba4fa..8f233b58a 100644
--- a/xmake/rules/c++/modules/modules_support/clang.lua
+++ b/xmake/rules/c++/modules/modules_support/clang.lua
@@ -115,11 +115,19 @@ function _get_modulemap_from_mapper(target, name)
     return common.localcache():get2(_mapper_cachekey(target), "modulemap" .. name) or nil
 end
 
--- enable libc++
-function _enable_libcxx(target)
-    target:add("cxxflags", "-stdlib=libc++")
-    target:add("ldflags", "-stdlib=libc++")
-    target:add("shflags", "-stdlib=libc++")
+-- use the given stdlib? e.g. libc++ or libstdc++
+function _use_stdlib(target, name)
+    local stdlib = target:data("cxx.modules.stdlib") or "libstdc++"
+    return stdlib == name
+end
+
+-- set stdlib flags, it will use libstdc++ if we do not set `-stdlib=`
+function _set_stdlib_flags(target)
+    if _use_stdlib(target, "libc++") then
+        target:add("cxxflags", "-stdlib=libc++")
+        target:add("ldflags", "-stdlib=libc++")
+        target:add("shflags", "-stdlib=libc++")
+    end
 end
 
 -- load module support for the current target
@@ -161,10 +169,12 @@ function load(target)
     -- sudo apt install libc++-dev libc++abi-15-dev
     --
     local flags = table.join(target:get("cxxflags") or {}, get_config("cxxflags") or {})
-    target:data_set("cxx.modules.use_libc++", table.contains(flags, "-stdlib=libc++", "clang::-stdlib=libc++"))
-    if target:data("cxx.modules.use_libc++") then
-        _enable_libcxx(target)
+    if table.contains(flags, "-stdlib=libc++", "clang::-stdlib=libc++") then
+        target:data_set("cxx.modules.stdlib", "libc++")
+    elseif table.contains(flags, "-stdlib=libstdc++", "clang::-stdlib=libstdc++") then
+        target:data_set("cxx.modules.stdlib", "libstdc++")
     end
+    _set_stdlib_flags(target)
 end
 
 -- get includedirs for stl headers
@@ -178,7 +188,7 @@ function _get_toolchain_includedirs_for_stlheaders(target, includedirs, clang)
     local tmpfile = os.tmpfile() .. ".cc"
     io.writefile(tmpfile, "#include <vector>")
     local argv = {"-E", "-x", "c++", tmpfile}
-    if target:data("cxx.modules.use_libc++") then
+    if _use_stdlib(target, "libc++") then
         table.insert(argv, 1, "-stdlib=libc++")
     end
     local result = try {function () return os.iorunv(clang, argv) end}
@@ -308,7 +318,6 @@ function generate_dependencies(target, sourcebatch, opt)
                 local compflags = compinst:compflags({sourcefile = sourcefile, target = target})
                 local flags = table.join("--format=p1689", "--",
                                          compinst:program(), "-x", "c++", "-c", sourcefile, "-o", target:objectfile(sourcefile),
-                                         "-stdlib=libc++",
                                          compflags)
                 vprint(table.concat(table.join(clangscandeps, flags), " "))
                 local outdata, errdata = os.iorunv(clangscandeps, flags)
@@ -335,7 +344,7 @@ function generate_dependencies(target, sourcebatch, opt)
             local rawdependinfo = io.readfile(jsonfile)
             if rawdependinfo then
                 local dependinfo = json.decode(rawdependinfo)
-                if not target:data("cxx.modules.use_libc++") then
+                if target:data("cxx.modules.stdlib") == nil then
                     local has_std_modules = false
                     for _, r in ipairs(dependinfo.rules) do
                         for _, required in ipairs(r.requires) do
@@ -361,10 +370,9 @@ function generate_dependencies(target, sourcebatch, opt)
                                they can be emulated through clang modules and supported only on libc++ ;
                                please add -stdlib=libc++ cxx flag or disable strict mode]])
 
-                        target:data_set("cxx.modules.use_libc++", true)
-                        if target:data("cxx.modules.use_libc++") then
-                            _enable_libcxx(target)
-                        end
+                        -- we use libc++ by default if we do not explicitly specify -stdlib:libstdc++
+                        target:data_set("cxx.modules.stdlib", "libc++")
+                        _set_stdlib_flags(target)
                     end
                 end
             end
@@ -403,7 +411,7 @@ function generate_stl_headerunits_for_batchjobs(target, batchjobs, headerunits,
 
                 end, {dependfile = target:dependfile(bmifile), files = {headerunit.path}})
                 -- libc++ have a builtin module mapper
-                if not target:data_set("cxx.modules.use_libc++") then
+                if not _use_stdlib(target, "libc++") then
                     _add_module_to_mapper(target, headerunit.name, bmifile)
                 end
             end, {rootjob = flushjob})
@@ -431,7 +439,7 @@ function generate_stl_headerunits_for_batchcmds(target, batchcmds, headerunits,
             _batchcmds_compile(batchcmds, target, flags)
         end
         -- libc++ have a builtin module mapper
-        if not target:data_set("cxx.modules.use_libc++") then
+        if not _use_stdlib(target, "libc++") then
             _add_module_to_mapper(target, headerunit.name, bmifile)
         end
         depmtime = math.max(depmtime, os.mtime(bmifile))
-- 
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