[RFC][PATCH 21/22] Add Makerules to build %.o and %.os from %.i8

[Joseph Myers]

On Wed, 21 Oct 2015, Gary Benson wrote:

> > On some platforms, even assembler files with no actual code need to
> > contain certain assembler directives to be ABI-compatible with those
> > generated by the compiler.  In particular, this applies to ARM; see
> > the .eabi_attribute directives in sysdeps/arm/sysdep.h.  If
> > generating a .S file, you should make sure it includes <sysdep.h> so
> > that such directives are present.
> 
> I did not know that.  Is this because all glibc files include this
> file with the directives?

Almost all .S files include <sysdep.h> to use its macros for defining 
functions etc. - and where they do not, special measures are needed on ARM 
(see sysdeps/arm/abi-note.S adding these attributes and then including 
csu/abi-note.S).  Including <sysdep.h> in generated .S files is the 
simplest way of ensuring such directives are present when required.

> (I guess what I'm asking is, in general, if I have a .c file and a
> .S file with no special directives, can I compile and link them and
> expect it to work?)

Not without these directives on ARM.

> For glibc is it ok if I add '-include sysdep.h' to the %.S -> %.o*
> rules?

I think that should work for these Infinity-generated files.

-- 
Joseph S. Myers
joseph@codesourcery.com