config: prevent the re-definition of a macro
This causes unnecessary warnings when building with `cl`. Newer
versions of the C standard permit the redefinition of the macro to the
same value (which is the case here), unfortunately, `cl` does not yet
implement this. Add a check to prevent the redefinition.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@293439 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__config b/include/__config
index e723180..1fedc04 100644
--- a/include/__config
+++ b/include/__config
@@ -12,8 +12,10 @@
#define _LIBCPP_CONFIG
#if defined(_MSC_VER) && !defined(__clang__)
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#define _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
#endif
+#endif
#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
#pragma GCC system_header
