[LLVMdev] Build Failure

David Blaikie dblaikie at gmail.com
Thu Jan 3 11:27:00 PST 2013

On Thu, Jan 3, 2013 at 11:16 AM,  <dag at cray.com> wrote:
> David Blaikie <dblaikie at gmail.com> writes:
>> Selfhost clang. Whenever we get a warning from Clang we either fix
>> Clang or fix the build quite quickly.
> Not possible,

Out of curiosity - why not? (sure, I realize everyone has internal
build systems, etc, that they're ultimately integrating LLVM into -
but that doesn't mean you have to do your development there (Google
has an internal build system & I could do my development there, but I
tend to develop with an upstream-style CMake+Ninja (& selfhosting)

>> If you want to fix the build such that LLVM can be built -Werror clean
>> with GCC the right solution is going to be to turn off -Wuninitialized
>> when the LLVM build system detects that it is using GCC rather than
>> Clang (we have the inverse, where we turn on certain Clang warning
>> flags when we detect that we're using Clang).
> I would like to keep -Wuninitialized if at all possible because it does
> in fact detect bugs.

I'm not saying it doesn't detect bugs. My statement(s) were made with
that (& other issues mentioned) in mind.

>> Pragmas: maybe, but it would probably muddy the waters a fair bit.
>> Depends how noisy any given warning is - I suspect -Wuninitialized
>> wouldn't meet the bar for pragma suppressions (there would be too many
>> suppressions) & should just be disabled in the build system when using
>> GCC. We can rely on Clang's warnings to catch things that can be
>> caught reliably.
> I really dislike disabling warnings if we can suppress them in specific
> cases.

It just depends how many cases there are. If it becomes a very common
suppression the pragmas will rather get in the way of working with the

> I can't use clang to catch things, gcc is my only option.

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