Re: [Xen-devel] [PATCH] x86: fix clang .macro retention check

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Nov 14, 2019 at 12:43:33PM +0100, Jan Beulich wrote:
> On 14.11.2019 10:38, Roger Pau Monné  wrote:
> > On Wed, Nov 13, 2019 at 06:01:40PM +0100, Jan Beulich wrote:
> >> --- a/xen/arch/x86/Rules.mk
> >> +++ b/xen/arch/x86/Rules.mk
> >> @@ -82,6 +64,6 @@ $(call as-option-add,CFLAGS,CC,".include
> >>  # Check whether clang keeps .macro-s between asm()-s:
> >>  # https://bugs.llvm.org/show_bug.cgi?id=36110
> >>  $(call as-option-add,CFLAGS,CC,\
> >> -                     ".macro FOO\n.endm\"); asm volatile (\".macro 
> >> FOO\n.endm",\
> >> +                     ".macro FOO\n.endm"$$(close); asm volatile 
> >> $$(open)".macro FOO\n.endm",\
> > 
> > Thanks, while here could you also replace the '\n' with a ';'? '\n'
> > doesn't work properly and gives me the following error:
> > 
> > <stdin>:1:32: error: missing terminating '"' character 
> > [-Werror,-Winvalid-pp-token]
> > void _(void) { asm volatile (  ".macro FOO
> >                                ^
> > <stdin>:1:32: error: expected string literal in 'asm'
> > <stdin>:3:6: error: missing terminating '"' character 
> > [-Werror,-Winvalid-pp-token]
> > .endm" ); }
> >      ^
> > <stdin>:3:12: error: expected ')'
> > .endm" ); }
> >            ^
> > <stdin>:1:29: note: to match this '('
> > void _(void) { asm volatile (  ".macro FOO
> >                             ^
> > <stdin>:3:12: error: expected '}'
> > .endm" ); }
> >            ^
> > <stdin>:1:14: note: to match this '{'
> > void _(void) { asm volatile (  ".macro FOO
> >              ^
> 
> So this must be yet another issue - I did specifically look at the what
> gets handed to the compiler, and I did not see the above. I wonder
> whether that's also related to the \" that I found necessary to drop -
> with what you say I'd expect the un-escaped double quotes won't work
> for you.

AFAIK those work fine.

> I suppose though this un-escaping (or not) happens at a level
> other than the compiler, i.e. either a difference in shell or in make
> behavior.

Maybe, I'm not an expert on shells or makefiles. This time I've tested
with Debian 9.5 instead of FreeBSD, so it's likely that what was there
worked fine on FreeBSD which I'm quite sure was what I testing against
back when I added this check.

This is what I used to test:

GNU Make 4.1
GNU bash, version 4.4.12(1)-release (x86_64-pc-linux-gnu)

Not sure whether there are other utilities involved in this behavior.

> IOW I don't think just replacing \n by ; will do.

I can give your patch a try with FreeBSD, but that's not going to
explain the different behavior I'm afraid.

Thanks, Roger.

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