Fix precompiled headers with clang-cl

Clang-cl couldn't find the header given to it by -FI when it isn't in any of the included directories. Additionally clang-cl 8 has a bug with exported templated classes with inline methods that causes it to have missing symbols at link time. We work around this. Fixes: QTBUG-74563 Change-Id: I7becf05fa8edb07bd4cefe12bee3737e5e1dfa14 Reviewed-by: Yuhang Zhao <[email protected]> Reviewed-by: Mårten Nordheim <[email protected]> Reviewed-by: Kai Koehne <[email protected]>
HoBoIs · Apr 9, 2019 · eaf2042 · eaf2042
1 parent fe7a8d6
commit eaf2042
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Showing 2 changed files with 12 additions and 7 deletions.
diff --git a/mkspecs/win32-clang-msvc/qmake.conf b/mkspecs/win32-clang-msvc/qmake.conf
@@ -44,7 +44,4 @@ QMAKE_CXXFLAGS_LTCG     = $$QMAKE_CFLAGS_LTCG
 # Leave QMAKE_LFLAGS_LTCG empty because lld-link doesn't need any additional parameters
 QMAKE_LFLAGS_LTCG       =
 
-# Precompiled headers are not supported yet by clang
-CONFIG -= precompile_header
-
 load(qt_config)
diff --git a/qmake/generators/win32/msvc_nmake.cpp b/qmake/generators/win32/msvc_nmake.cpp
@@ -165,10 +165,14 @@ QString NmakeMakefileGenerator::var(const ProKey &value) const
                                || value == "QMAKE_RUN_CXX_IMP"
                                || value == "QMAKE_RUN_CXX");
         if ((isRunCpp && usePCH) || (isRunC && usePCHC)) {
-            QFileInfo precompHInfo(fileInfo(precompH));
-            QString precompH_f = escapeFilePath(precompHInfo.fileName());
+            QString precompH_f = escapeFilePath(fileFixify(precompH, FileFixifyBackwards));
             QString precompRule = QString("-c -FI%1 -Yu%2 -Fp%3")
                     .arg(precompH_f, precompH_f, escapeFilePath(isRunC ? precompPchC : precompPch));
+            // ### For clang_cl 8 we force inline methods to be compiled here instead
+            // linking them from a pch.o file. We do this by pretending we are also doing
+            // the pch.o generation step.
+            if (project->isActiveConfig("clang_cl"))
+                precompRule += QString(" -Xclang -building-pch-with-obj");
             QString p = MakefileGenerator::var(value);
             p.replace(QLatin1String("-c"), precompRule);
             return p;
@@ -230,7 +234,10 @@ void NmakeMakefileGenerator::init()
         precompObj = var("PRECOMPILED_DIR") + project->first("TARGET") + "_pch" + Option::obj_ext;
         precompPch = var("PRECOMPILED_DIR") + project->first("TARGET") + "_pch.pch";
         // Add linking of precompObj (required for whole precompiled classes)
-        project->values("OBJECTS") += precompObj;
+        // ### For clang_cl we currently let inline methods be generated in the normal objects,
+        // since the PCH object is buggy (as of clang 8.0.0)
+        if (!project->isActiveConfig("clang_cl"))
+            project->values("OBJECTS") += precompObj;
         // Add pch file to cleanup
         project->values("QMAKE_CLEAN") += precompPch;
         // Return to variable pool
@@ -240,7 +247,8 @@ void NmakeMakefileGenerator::init()
     if (usePCHC) {
         precompObjC = var("PRECOMPILED_DIR") + project->first("TARGET") + "_pch_c" + Option::obj_ext;
         precompPchC = var("PRECOMPILED_DIR") + project->first("TARGET") + "_pch_c.pch";
-        project->values("OBJECTS") += precompObjC;
+        if (!project->isActiveConfig("clang_cl"))
+            project->values("OBJECTS") += precompObjC;
         project->values("QMAKE_CLEAN") += precompPchC;
         project->values("PRECOMPILED_OBJECT_C") = ProStringList(precompObjC);
         project->values("PRECOMPILED_PCH_C")    = ProStringList(precompPchC);