[LLVMdev] Problem with InsertPointGuard ABI?

[Paweł Bylica]

On Tue, Jul 21, 2015 at 6:30 PM Justin Bogner <mail at justinbogner.com> wrote:

> Paweł Bylica <chfast at gmail.com> writes:
> > On Tue, Jul 21, 2015 at 5:55 PM Justin Bogner <mail at justinbogner.com>
> wrote:
> >
> >     Paweł Bylica <chfast at gmail.com> writes:
> >     > I can confirm that the issue has been caused by NDEBUG flag.
> >     >
> >     > On Mon, Jul 13, 2015 at 6:29 PM Reid Kleckner <rnk at google.com>
> wrote:
> >     >
> >     >     The layout of AssertingVH has depended on NDEBUG since 2009,
> which
> >     >     predates any of our efforts to make LLVM's ABI resilient to
> >     mismatched
> >     >     NDEBUG definitions between LLVM and its users.
> >     >
> >     >     For now, make sure your definition of NDEBUG matches LLVM's.
> In the
> >     long
> >     >     run, we could conceivably do something
> >     >     with LLVM_ENABLE_ABI_BREAKING_CHECKS to allow this mismatch.
> >     >
> >     > In practice it is very hard to make NDEBUG flag match configs of
> your
> >     project
> >     > and LLVM project. You often need to build debug and release
> versions of
> >     your
> >     > project and LLVM is installed as a debian package or with homebrew.
> >     Moreover,
> >     > there is not reliable way of checking if LLVM has been built with
> or
> >     without
> >     > NDEBUG.
> >
> >     FWIW, `llvm-config --assertion-mode` will tell you whether or not
> your
> >     LLVM was built with or without NDEBUG.
> >
> > That's not true in all cases. In case CMAKE_BUILD_TYPE=Release,
> > LLVM_ENABLE_ASSERTIONS=Off and CMAKE_CXX_FLAGS_RELEASE="" llvm-config
> reports
> > asserts as off but NDEBUG flag is not set.
>
> Um, okay, but why would you set CMAKE_CXX_FLAGS_RELEASE=""? That doesn't
> make any sense...
>

I agree, it make no sense. But homebrew actually does that:
https://github.com/Homebrew/homebrew/blob/master/Library/Homebrew/formula.rb#L615

There are many possible solutions for this case:
1. Force NDEBUG flag
2. Report a cmake error.
3. Get rid of LLVM_ENABLE_ASSERTIONS flag and relay on NDEBUG flag only.


>
> >
> >     > Can I do anything more about it? Contributions related to
> >     >  LLVM_ENABLE_ABI_BREAKING_CHECKS needed?
> >     >
> >     > - Paweł
> >     >
> >     > _______________________________________________
> >     > LLVM Developers mailing list
> >     > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >     > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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