r220714 - Frontend: Define __EXCEPTIONS if -fexceptions is passed

[Richard Smith]

On Thu, Dec 4, 2014 at 4:01 PM, Nico Weber <thakis at chromium.org> wrote:

> This doesn't look right. Isn't cc1 -fexceptions passed if either ObjC or
> C++ exceptions are enabled?
>

Right, this change doesn't make sense to me; Clang's -cc1 interface has no
compatibility goal with GCC's cc1plus, and we should only be defining
__EXCEPTIONS if the *driver* has -fexceptions passed to it.

Perhaps the issue is that the driver should be forwarding -fexceptions to
-fcxx-exceptions in more cases?


> As is, it looks like this breaks this lovely bit of code from breakpad in
> a .mm file:
>
> #ifndef __EXCEPTIONS
> // This file uses C++ try/catch (but shouldn't). Duplicate the macros from
> // <c++/4.2.1/exception_defines.h> allowing this file to work properly with
> // exceptions disabled even when other C++ libraries are used. #undef the
> try
> // and catch macros first in case libstdc++ is in use and has already
> provided
> // its own definitions.
> #undef try
> #define try       if (true)
> #undef catch
> #define catch(X)  if (false)
> #endif  // __EXCEPTIONS
>
> even though that file is built with an explicit -fno-exceptions. Repro:
>
> $ bin/clang -fno-exceptions -x objective-c++ -dM /dev/null -E | grep EXCE
> #define OBJC_ZEROCOST_EXCEPTIONS 1
> #define __EXCEPTIONS 1
>
> On Mon, Oct 27, 2014 at 1:02 PM, David Majnemer <david.majnemer at gmail.com>
> wrote:
>
>> Author: majnemer
>> Date: Mon Oct 27 15:02:19 2014
>> New Revision: 220714
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=220714&view=rev
>> Log:
>> Frontend: Define __EXCEPTIONS if -fexceptions is passed
>>
>> GCC defines __EXCEPTIONS, regardless of language mode, if -fexceptions
>> is passed.  We should do the same.
>>
>> This fixes PR21358.
>>
>> Modified:
>>     cfe/trunk/lib/Frontend/InitPreprocessor.cpp
>>     cfe/trunk/test/Frontend/exceptions.c
>>     cfe/trunk/test/Preprocessor/predefined-exceptions.m
>>
>> Modified: cfe/trunk/lib/Frontend/InitPreprocessor.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/InitPreprocessor.cpp?rev=220714&r1=220713&r2=220714&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Frontend/InitPreprocessor.cpp (original)
>> +++ cfe/trunk/lib/Frontend/InitPreprocessor.cpp Mon Oct 27 15:02:19 2014
>> @@ -550,7 +550,7 @@ static void InitializePredefinedMacros(c
>>      Builder.defineMacro("__BLOCKS__");
>>    }
>>
>> -  if (!LangOpts.MSVCCompat && LangOpts.CXXExceptions)
>> +  if (!LangOpts.MSVCCompat && LangOpts.Exceptions)
>>      Builder.defineMacro("__EXCEPTIONS");
>>    if (!LangOpts.MSVCCompat && LangOpts.RTTI)
>>      Builder.defineMacro("__GXX_RTTI");
>>
>> Modified: cfe/trunk/test/Frontend/exceptions.c
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Frontend/exceptions.c?rev=220714&r1=220713&r2=220714&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Frontend/exceptions.c (original)
>> +++ cfe/trunk/test/Frontend/exceptions.c Mon Oct 27 15:02:19 2014
>> @@ -1,6 +1,9 @@
>> -// RUN: %clang_cc1 -fms-compatibility -fexceptions -fcxx-exceptions
>> -verify %s
>> +// RUN: %clang_cc1 -fms-compatibility -fexceptions -fcxx-exceptions
>> -DMS_MODE -verify %s
>>  // expected-no-diagnostics
>>
>> -#if defined(__EXCEPTIONS)
>> +// RUN: %clang_cc1 -fms-compatibility -fexceptions -verify %s
>> +// expected-no-diagnostics
>> +
>> +#if defined(MS_MODE) && defined(__EXCEPTIONS)
>>  #error __EXCEPTIONS should not be defined.
>>  #endif
>>
>> Modified: cfe/trunk/test/Preprocessor/predefined-exceptions.m
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Preprocessor/predefined-exceptions.m?rev=220714&r1=220713&r2=220714&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Preprocessor/predefined-exceptions.m (original)
>> +++ cfe/trunk/test/Preprocessor/predefined-exceptions.m Mon Oct 27
>> 15:02:19 2014
>> @@ -1,6 +1,6 @@
>>  // RUN: %clang_cc1 -x objective-c -fobjc-exceptions -fexceptions -E -dM
>> %s | FileCheck -check-prefix=CHECK-OBJC-NOCXX %s
>>  // CHECK-OBJC-NOCXX: #define OBJC_ZEROCOST_EXCEPTIONS 1
>> -// CHECK-OBJC-NOCXX-NOT: #define __EXCEPTIONS 1
>> +// CHECK-OBJC-NOCXX: #define __EXCEPTIONS 1
>>
>>  // RUN: %clang_cc1 -x objective-c++ -fobjc-exceptions -fexceptions
>> -fcxx-exceptions -E -dM %s | FileCheck -check-prefix=CHECK-OBJC-CXX %s
>>  // CHECK-OBJC-CXX: #define OBJC_ZEROCOST_EXCEPTIONS 1
>>
>>
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>
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