Re: [patch] Use __builtin_FILE and __builtin_LINE in assert implementation in C++

[Rich Felker <dalias@libc.org>]

On Mon, Jan 23, 2023 at 03:26:04PM +0100, Florian Weimer via Libc-alpha wrote:
> * Paul Pluzhnikov via Libc-alpha:
> 
> > diff --git a/assert/assert.h b/assert/assert.h
> > index 72209bc5e7..4e0303db8d 100644
> > --- a/assert/assert.h
> > +++ b/assert/assert.h
> > @@ -89,7 +89,8 @@ __END_DECLS
> >  #  define assert(expr)                                                 \
> >       (static_cast <bool> (expr)
> >          \
> >        ? void (0)                                                       \
> > -      : __assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION))
> > +      : __assert_fail (#expr, __builtin_FILE (), __builtin_LINE (),     \
> > +                       __ASSERT_FUNCTION))
> >  # elif !defined __GNUC__ || defined __STRICT_ANSI__
> >  #  define assert(expr)                                                 \
> >      ((expr)                                                            \
> 
> I think __builtin_FILE and __builtin_LINE are farily recent GCC/Clang
> additions, so they need compiler version checks or a __has_builtin gate.
> 
> Ideally, we would use <source_location> here, but I don't think we can
> include that from <assert.h>.
> 
> Thanks,
> Florian

Why not instead:

+static char *__file_for_assert = __FILE__;
...
-      : __assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION))
+      : __assert_fail (#expr, __file_for_assert, __LINE__, __ASSERT_FUNCTION))

??

No need for any version dependent and nonportable builtins.

Rich