Re: [PATCH] Fix PR33168, ppc64 bootstrap failure

[Segher Boessenkool <segher at kernel dot crashing dot org>]

> > This patch from Segher fixes the bootstrap failure on ppc64.

> I think this patch is papering over the real bug.  It isn't legitimate
> to mix read-write and read-only section statements.  E.g.:
>
> 	.section	.foo,"a",@progbits
> 	.section	.foo,"aw",@progbits

Yes.

> produces an unconditional warning:
>
> Warning: ignoring changed section attributes for .foo
>
> so it seems dangerous for gcc to allow it, especially in cases where 
> the
> user hasn't even used section attributes.

My patch was _supposed_ to only do this when there _is_ a section
attribute on both declarations.  I think I messed that up though,
which is why I haven't been pushing this patch anymore.

I _do_ still think that when the compiler decides a user-declared 
section
should be r/w because of one declaration, but r/o is "good enough" for
another, it should make the section r/w; i.e., from gcc.dg/20051207.c:

	int a __attribute__((section (".eh_frame"))) = 1;
	const int b __attribute__((section (".eh_frame"))) = 1;

shouldn't fail.

There really should be syntax for the user to specify section attributes
directly.

> It sounds like the real bug is what Alan describes in comment #11,
> namely that the front end is changing something's visiblity after
> having created RTL for it.

Looks like it yes.

Btw, did the patch in comment #8 ever get backported to 4.2?  Without 
it,
compiling the Linux kernel fails for many configs (on ppc64).


Segher