add a proper warning when falling back to fallback module scanner for gcc and clang

2 files changed, 10 insertions, 2 deletions

diff --git a/xmake/rules/c++/modules/modules_support/clang/dependency_scanner.lua b/xmake/rules/c++/modules/modules_support/clang/dependency_scanner.lua
index 009bf519a..4bc15dbde 100644
--- a/xmake/rules/c++/modules/modules_support/clang/dependency_scanner.lua
+++ b/xmake/rules/c++/modules/modules_support/clang/dependency_scanner.lua
@@ -38,7 +38,8 @@ function generate_dependency_for(target, sourcefile, opt)
 
         local outputdir = compiler_support.get_outputdir(target, sourcefile)
         local jsonfile = path.translate(path.join(outputdir, path.filename(sourcefile) .. ".json"))
-        if compiler_support.has_clangscandepssupport(target) and not target:policy("build.c++.clang.fallbackscanner") then
+        local has_clangscandepssupport = compiler_support.has_clangscandepssupport(target)
+        if has_clangscandepssupport and not target:policy("build.c++.clang.fallbackscanner") then
             -- We need absolute path of clang to use clang-scan-deps
             -- See https://clang.llvm.org/docs/StandardCPlusPlusModules.html#possible-issues-failed-to-find-system-headers
             local clang_path = compinst:program()
@@ -57,6 +58,9 @@ function generate_dependency_for(target, sourcefile, opt)
 
             io.writefile(jsonfile, outdata)
         else
+            if not has_clangscandepssupport then
+                wprint("No clang-scan-deps found ! using fallback scanner")
+            end
             fallback_generate_dependencies(target, jsonfile, sourcefile, function(file)
                 local keepsystemincludesflag = compiler_support.get_keepsystemincludesflag(target)
                 local compflags = compinst:compflags({sourcefile = file, target = target})
diff --git a/xmake/rules/c++/modules/modules_support/gcc/dependency_scanner.lua b/xmake/rules/c++/modules/modules_support/gcc/dependency_scanner.lua
index 8cdb0a0a3..38d7c6069 100644
--- a/xmake/rules/c++/modules/modules_support/gcc/dependency_scanner.lua
+++ b/xmake/rules/c++/modules/modules_support/gcc/dependency_scanner.lua
@@ -44,7 +44,8 @@ function generate_dependency_for(target, sourcefile, opt)
 
         local outputdir = compiler_support.get_outputdir(target, sourcefile)
         local jsonfile = path.translate(path.join(outputdir, path.filename(sourcefile) .. ".json"))
-        if depsformatflag and depsfileflag and depstargetflag and not target:policy("build.c++.gcc.fallbackscanner") then
+        local has_depsflags = depsformatflag and depsfileflag and depstargetflag
+        if has_depsflags and not target:policy("build.c++.gcc.fallbackscanner") then
             local ifile = path.translate(path.join(outputdir, path.filename(sourcefile) .. ".i"))
             local dfile = path.translate(path.join(outputdir, path.filename(sourcefile) .. ".d"))
             local compflags = compinst:compflags({sourcefile = sourcefile, target = target})
@@ -53,6 +54,9 @@ function generate_dependency_for(target, sourcefile, opt)
             os.rm(ifile)
             os.rm(dfile)
         else
+            if not has_depsflags then
+                wprint("GCC doesn't support module scanning ! using fallback scanner")
+            end
             fallback_generate_dependencies(target, jsonfile, sourcefile, function(file)
                 local compflags = compinst:compflags({sourcefile = file, target = target})
                 -- exclude -fmodule* flags because, when they are set gcc try to find bmi of imported modules but they don't exists a this point of compilation