RunClang: Avoid GNU extensions in glibc math headers on i386

On i386 with optimizations enabled, the `bits/mathinline.h` header may
use a GNU extension not implemented by Clang.  Avoid parsing this code
by defining `__NO_MATH_INLINES` so it will be preprocessed out.

GitHub-Issue: #47

1 files changed, 14 insertions, 0 deletions

diff --git a/src/RunClang.cxx b/src/RunClang.cxx
index 9768a25..0a68698 100644
--- a/src/RunClang.cxx
+++ b/src/RunClang.cxx
@@ -204,6 +204,13 @@ protected:
         }
       }
 
+      // Prevent glibc use of a GNU extension not implemented by Clang.
+      if (this->NeedNoMathInlines(this->Opts.Predefines)) {
+        builtins += "\n"
+          "#define __NO_MATH_INLINES 1\n"
+          ;
+      }
+
     } else {
       builtins += predefines.substr(start, end-start);
     }
@@ -229,6 +236,13 @@ protected:
              pd.find("#define __ia64__ ") != pd.npos));
   }
 
+  bool NeedNoMathInlines(std::string const& pd) const {
+    return (this->IsActualGNU(pd) &&
+            (pd.find("#define __i386__ ") != pd.npos &&
+             pd.find("#define __OPTIMIZE__ ") != pd.npos &&
+             pd.find("#define __NO_MATH_INLINES ") == pd.npos));
+  }
+
   bool BeginSourceFileAction(clang::CompilerInstance& CI,
                              llvm::StringRef /*Filename*/) {
     CI.getPreprocessor().setPredefines(this->UpdatePredefines(CI));