[cfe-dev] On preserving unused file-local definitions at -O0

[Robinson, Paul]

> -----Original Message-----
> From: David Blaikie [mailto:dblaikie at gmail.com]
> Sent: Friday, April 11, 2014 11:34 AM
> To: Robinson, Paul
> Cc: cfe-dev Developers; Eric Christopher
> Subject: Re: [cfe-dev] On preserving unused file-local definitions at -
> O0
> 
> On Fri, Apr 11, 2014 at 9:46 AM, Robinson, Paul
> <Paul_Robinson at playstation.sony.com> wrote:
> >> For Clang, run the GDB suite with -femit_all_decls ?
> >> --paulr
> >
> > Speling it korecly, -femit-all-decls (duh).
> 
> Huh - I think I vaguely knew about that flag at some point & forgot
> again (or never knew about it in the first place).
> 
> Neat-ish. Poor name of the flag (given it's about definitions, not
> declarations).
> 
> Still want to try to get the GDB test suite clean with clang's default
> configuration, ideally, one way or another. But actually the
> difference in behavior between GCC's default and Clang's default or
> Clang with -femit-all-decls is an interesting point. Clang either
> emits 'everything' (unused static definitions and unused inline
> definitions) or nothing. GCC is somewhere in the middle (emits unused
> static definitions, but doesn't emit unused inline definitions) - so
> perhaps that's a useful point to make to the GDB community that GCC
> doesn't have a strong principle here... maybe. (I can see some
> possible counterarguments already, though)
> 
> - David

Right, and you start straying into questions of whether the GDB test
suite is more properly verifying GDB's behavior or the compiler's
behavior.  I think it's a highly desirable goal to ensure that Clang's
output can be consumed by GDB, which is not quite the same thing as
ensuring that Clang's default behavior satisfies the assumptions made
by the GDB test suite.

All good fodder for an LLVM-social discussion, sometime.
--paulr