[cfe-commits] [patch] Fix -fno-exceptions for c++

[Douglas Gregor]

On Sep 28, 2009, at 4:31 PM, Rafael Espindola wrote:

> Currently __EXCEPTIONS=1 is always defined when compiling c++. The
> attached patch fixes it:
>
> clang -E -fno-exceptions test.c        disabled
> clang -E -fexceptions test.c             enabled
> clang -E test.c                               disabled
> clang -E -fno-exceptions test.cc      disabled
> clang -E -fexceptions test.cc           enabled
> clang -E test.cc                             enabled
>
> But it looks silly :-)
>
> Is there a way in clang-cc to test that an option was not given (as
> opposed to having the default value)?

I think the getPosition() member function will return > 0 when an  
option was given, 0 when it was not given.

The -fexceptions/-fno-exceptions option and the current language  
dialect should be used to set the Exceptions field of LangOptions. We  
shouldn't do this:

Index: include/clang/Basic/LangOptions.h
===================================================================
--- include/clang/Basic/LangOptions.h	(revision 83024)
+++ include/clang/Basic/LangOptions.h	(working copy)
@@ -44,6 +44,7 @@
    unsigned LaxVectorConversions : 1;
    unsigned AltiVec           : 1;  // Support AltiVec-style vector  
initializers.
    unsigned Exceptions        : 1;  // Support exception handling.
+  unsigned NoExceptions      : 1;  // Don't support exception handling.
    unsigned Rtti              : 1;  // Support rtti information.

    unsigned NeXTRuntime       : 1; // Use NeXT runtime.

because all clients would have to reason about -fexceptions/-fno- 
exceptions/language defauls, PCH would have to serialize NoExceptions,  
etc.

	- Doug