Autogen: Pass explicit predefines header to moc if possible

Qt is relying on whoever calls moc to include a file with the predefined
values that will be used by the compiler, otherwise moc takes wrong
paths and weird things happen.
Instead, generate an include file and feed it to all mocs to make sure
it's generating correct code.

Co-Author: Sebastian Holtermann <sebholt@xwmw.org>
Fixes: #16640

1 files changed, 41 insertions, 0 deletions

diff --git a/Source/cmQtAutoGeneratorInitializer.cxx b/Source/cmQtAutoGeneratorInitializer.cxx
index d69794c743..c7e02e66bd 100644
--- a/Source/cmQtAutoGeneratorInitializer.cxx
+++ b/Source/cmQtAutoGeneratorInitializer.cxx
@@ -96,6 +96,41 @@ static std::string GetQtMajorVersion(cmGeneratorTarget const* target)
   return qtMajorVersion;
 }
 
+static std::string GetQtMinorVersion(cmGeneratorTarget const* target,
+                                     const std::string& qtMajorVersion)
+{
+  cmMakefile* makefile = target->Target->GetMakefile();
+  std::string qtMinorVersion;
+  if (qtMajorVersion == "5") {
+    qtMinorVersion = makefile->GetSafeDefinition("Qt5Core_VERSION_MINOR");
+  }
+  if (qtMinorVersion.empty()) {
+    qtMinorVersion = makefile->GetSafeDefinition("QT_VERSION_MINOR");
+  }
+
+  const char* targetQtVersion =
+    target->GetLinkInterfaceDependentStringProperty("QT_MINOR_VERSION", "");
+  if (targetQtVersion != CM_NULLPTR) {
+    qtMinorVersion = targetQtVersion;
+  }
+  return qtMinorVersion;
+}
+
+static bool QtVersionGreaterOrEqual(const std::string& major,
+                                    const std::string& minor,
+                                    unsigned long requestMajor,
+                                    unsigned long requestMinor)
+{
+  unsigned long majorUL(0);
+  unsigned long minorUL(0);
+  if (cmSystemTools::StringToULong(major.c_str(), &majorUL) &&
+      cmSystemTools::StringToULong(minor.c_str(), &minorUL)) {
+    return (majorUL > requestMajor) ||
+      (majorUL == requestMajor && minorUL >= requestMinor);
+  }
+  return false;
+}
+
 static void GetCompileDefinitionsAndDirectories(
   cmGeneratorTarget const* target, const std::string& config,
   std::string& incs, std::string& defs)
@@ -258,6 +293,12 @@ static void MocSetupAutoTarget(
   AddDefinitionEscaped(makefile, "_moc_depend_filters",
                        GetSafeProperty(target, "AUTOMOC_DEPEND_FILTERS"));
 
+  if (QtVersionGreaterOrEqual(
+        qtMajorVersion, GetQtMinorVersion(target, qtMajorVersion), 5, 8)) {
+    AddDefinitionEscaped(
+      makefile, "_moc_predefs_cmd",
+      makefile->GetSafeDefinition("CMAKE_CXX_COMPILER_PREDEFINES_COMMAND"));
+  }
   // Moc includes and compile definitions
   {
     std::string _moc_incs;