Fix a bug that warnings generated with -M or -MM flags

This is a patch for bug: https://bugs.llvm.org/show_bug.cgi?id=6817

Warnings should not be emitted with -M and -MM flags, because this mode
is only used for generate MakeFiles.

llvm-svn: 305561

2 files changed, 15 insertions, 0 deletions

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 6d3dbb5b520..bd4e894d650 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -980,6 +980,9 @@ void Clang::AddPreprocessingOptions(Compilation &C, const JobAction &JA,
         DepTarget = Args.MakeArgString(llvm::sys::path::filename(P));
       }
 
+      if (!A->getOption().matches(options::OPT_MD) && !A->getOption().matches(options::OPT_MMD)) {
+        CmdArgs.push_back("-w");
+      }
       CmdArgs.push_back("-MT");
       SmallString<128> Quoted;
       QuoteTarget(DepTarget, Quoted);
diff --git a/clang/test/Driver/m_and_mm.c b/clang/test/Driver/m_and_mm.c
index 18cf7abfa62..e4d59bc70e2 100644
--- a/clang/test/Driver/m_and_mm.c
+++ b/clang/test/Driver/m_and_mm.c
@@ -1,3 +1,15 @@
 // RUN: %clang -### \
 // RUN:   -M -MM %s 2> %t
 // RUN: not grep '"-sys-header-deps"' %t
+
+// RUN: %clang -M -MM %s 2> %t
+// RUN: not grep "warning" %t
+
+// RUN: %clang -MMD -MD %s 2> %t
+// RUN: grep "warning" %t
+
+#warning "This warning shouldn't show up with -M and -MM"
+int main (void)
+{
+    return 0;
+}