[cfe-dev] Warnings when building with gcc-4.5

[Douglas Gregor]

On Jun 7, 2010, at 7:58 PM, Mulder, Jonathan wrote:

> I know this was a long time back (I kinda forgot about this, sorry), but I was wondering if this was the proper way to silence these warnings.  Basically, I did it for APValue as a first go, and if it works I will keep on pruning out the errors. All I did was put a (void *) cast in between the other errors to silence the gcc warnings.
> 
> Let me know what you think...

We went ahead and added -fno-strict-aliasing, since we've run into too many false positives with these particular warnings and we don't want to uglify the code with so many (void*) casts.

	- Doug

> Jon
> 
> On Mon, May 10, 2010 at 1:27 PM, Douglas Gregor <dgregor at apple.com> wrote:
> 
> On May 6, 2010, at 8:04 AM, Mulder, Jonathan wrote:
> 
> > Hello all,
> >
> > I have been compiling clang using the stock gcc on apple (4.2.1) for awhile with no issues or warnings, but now I am trying to compile clang using the gcc 4.5.0 release, and I am getting a bunch of warnings of this variety.
> >
> > llvm[4]: Compiling ParseExprCXX.cpp for Debug build
> > ParseExprCXX.cpp: In member function ‘clang::Parser::OwningExprResult clang::Parser::ParseCXXAmbiguousParenExpression(clang::Parser::ParenParseOption&, clang::Parser::TypeTy*&, clang::SourceLocation, clang::SourceLocation&)’:
> > ParseExprCXX.cpp:1774:54: warning: converting ‘false’ to pointer type for argument 4 of ‘clang::Parser::OwningExprResult clang::Parser::ParseCastExpression(bool, bool, bool&, clang::Parser::TypeTy*)’
> >
> > llvm[2]: Compiling ExecutionEngineTest.cpp for Debug build
> > ExecutionEngineTest.cpp: In member function ‘virtual void<unnamed>::ExecutionEngineTest_ForwardGlobalMapping_Test::TestBody()’:
> > ExecutionEngineTest.cpp:52:3: warning: passing NULL to non-pointer argument 3 of ‘static testing::AssertionResult testing::internal::EqHelper<true>::Compare(const char*, const char*, const T1&, T2*) [with T1 = int, T2 = void]’
> >
> > Where they are either booleans (generally false values) being converted to pointer types, or the latter of passing NULL to non-pointer types.  If you could enlighten me as to the proper way to silence these warning I would be happy to go through them all and submit a patch.
> 
> These look like potential bugs in LLVM and Clang, each of which will have to be considered. If you're willing to fix these cases and provide a patch, that would be wonderful.
> 
> (Clang should probably warn about these kinds of conversions, too!)
> 
>        - Doug
> 
> <APValueStrictAliasing.patch>

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