From e9d7d78ab391dca1dbc05ab8876d58e8a7f6256c Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 3 Nov 2009 19:50:27 +0000
Subject: [PATCH] Implement support for the -undef command line option, patch
 by Roman Divacky! PR5363

llvm-svn: 85932
---
 clang/include/clang/Frontend/InitPreprocessor.h | 3 ++-
 clang/lib/Driver/Tools.cpp                      | 2 ++
 clang/lib/Frontend/InitPreprocessor.cpp         | 8 +++++---
 clang/test/Preprocessor/macro_undef.c           | 4 ++++
 clang/tools/clang-cc/clang-cc.cpp               | 5 ++++-
 5 files changed, 17 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/Preprocessor/macro_undef.c

diff --git a/clang/include/clang/Frontend/InitPreprocessor.h b/clang/include/clang/Frontend/InitPreprocessor.h
index eb03602dc57b..b29ee2728a86 100644
--- a/clang/include/clang/Frontend/InitPreprocessor.h
+++ b/clang/include/clang/Frontend/InitPreprocessor.h
@@ -63,7 +63,8 @@ public:
 /// environment ready to process a single file. This returns true on error.
 ///
 bool InitializePreprocessor(Preprocessor &PP,
-                            const PreprocessorInitOptions& InitOptions);
+                            const PreprocessorInitOptions& InitOptions,
+                            bool undef_macros);
 
 } // end namespace clang
 
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 47234ef64925..521c90dc31e5 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -1015,6 +1015,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       II.getInputArg().renderAsInput(Args, CmdArgs);
   }
 
+  Args.AddAllArgs(CmdArgs, options::OPT_undef);
+
   const char *Exec =
     Args.MakeArgString(getToolChain().GetProgramPath(C, "clang-cc"));
   Dest.addCommand(new Command(JA, Exec, CmdArgs));
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 2719fbb456c0..ec5c1061bb93 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -443,7 +443,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
 /// environment ready to process a single file. This returns true on error.
 ///
 bool clang::InitializePreprocessor(Preprocessor &PP,
-                                   const PreprocessorInitOptions &InitOpts) {
+                                   const PreprocessorInitOptions &InitOpts,
+                                   bool undef_macros) {
   std::vector<char> PredefineBuffer;
 
   const char *LineDirective = "# 1 \"<built-in>\" 3\n";
@@ -451,8 +452,9 @@ bool clang::InitializePreprocessor(Preprocessor &PP,
                          LineDirective, LineDirective+strlen(LineDirective));
 
   // Install things like __POWERPC__, __GNUC__, etc into the macro table.
-  InitializePredefinedMacros(PP.getTargetInfo(), PP.getLangOptions(),
-                             PredefineBuffer);
+  if (!undef_macros)
+    InitializePredefinedMacros(PP.getTargetInfo(), PP.getLangOptions(),
+                               PredefineBuffer);
 
   // Add on the predefines from the driver.  Wrap in a #line directive to report
   // that they come from the command line.
diff --git a/clang/test/Preprocessor/macro_undef.c b/clang/test/Preprocessor/macro_undef.c
new file mode 100644
index 000000000000..4507cddcb796
--- /dev/null
+++ b/clang/test/Preprocessor/macro_undef.c
@@ -0,0 +1,4 @@
+// RUN: clang-cc -dM -undef -Dfoo=1 -E %s | FileCheck %s
+
+// CHECK-NOT: #define __clang__
+// CHECK: #define foo 1
diff --git a/clang/tools/clang-cc/clang-cc.cpp b/clang/tools/clang-cc/clang-cc.cpp
index 5840f5f9900b..71e546980007 100644
--- a/clang/tools/clang-cc/clang-cc.cpp
+++ b/clang/tools/clang-cc/clang-cc.cpp
@@ -932,6 +932,9 @@ static bool InitializeSourceManager(Preprocessor &PP,
 //   -A...    - Play with #assertions
 //   -undef   - Undefine all predefined macros
 
+static llvm::cl::opt<bool>
+undef_macros("undef", llvm::cl::value_desc("macro"), llvm::cl::desc("undef all system defines"));
+
 static llvm::cl::list<std::string>
 D_macros("D", llvm::cl::value_desc("macro"), llvm::cl::Prefix,
        llvm::cl::desc("Predefine the specified macro"));
@@ -1243,7 +1246,7 @@ public:
 
     PreprocessorInitOptions InitOpts;
     InitializePreprocessorInitOptions(InitOpts);
-    if (InitializePreprocessor(*PP, InitOpts))
+    if (InitializePreprocessor(*PP, InitOpts, undef_macros))
       return 0;
 
     return PP.take();