RunClang: Tolerate __builtin_va_arg_pack during parsing

When simulating preprocessing by a GNU compiler code (in the standard
library) may try to use this builtin, but Clang does not support it.
Provide a fake instance of the builtin using a preprocessor macro good
enough to get through parsing references to it in function bodies.

GitHub-Issue: #46

1 files changed, 14 insertions, 0 deletions

diff --git a/src/RunClang.cxx b/src/RunClang.cxx
index 1259628..9768a25 100644
--- a/src/RunClang.cxx
+++ b/src/RunClang.cxx
@@ -180,6 +180,16 @@ protected:
     if (this->Opts.HaveCC) {
       builtins += this->Opts.Predefines;
 
+      // Provide __builtin_va_arg_pack if simulating the actual GNU compiler.
+      if (this->NeedBuiltinVarArgPack(this->Opts.Predefines)) {
+        // Clang does not support this builtin, so fake it to tolerate
+        // uses in function bodies while parsing.
+        builtins += "\n"
+          "#define __builtin_va_arg_pack() 0\n"
+          "#define __builtin_va_arg_pack_len() 1\n"
+          ;
+      }
+
       // Provide __float128 if simulating the actual GNU compiler.
       if (this->NeedFloat128(this->Opts.Predefines)) {
         // Clang provides its own (fake) builtin in gnu++11 mode.
@@ -208,6 +218,10 @@ protected:
             pd.find("#define __PGI ") == pd.npos);
   }
 
+  bool NeedBuiltinVarArgPack(std::string const& pd) {
+    return this->IsActualGNU(pd);
+  }
+
   bool NeedFloat128(std::string const& pd) const {
     return (this->IsActualGNU(pd) &&
             (pd.find("#define __i386__ ") != pd.npos ||