gas debugging info vs cpp

gas debugging info vs cpp

[Roland McGrath]

I recently became aware of the --gdwarf2/--gstabs options to gas, and was
pleased to find that gcc -g turns the appropriate one on automagically when
you use gcc to run the assembler.  For example, 

	$ gcc -c -g foo.S

et voila, I have a foo.o with perfectly lovely DWARF2 information about
the line numbers in a file called /tmp/ccXQLg55.s!  Mighty handy.

So, I would like to fix this.  The question is, what needs to be fixed?
The assembler can learn to grok cpp # lines, or cpp can learn to emit
assembler .file/.line directives.  

The assembler can't just change, since cpp # lines are assembler comments.
So it would need a switch to tell it to grok cpp # lines.  Then gcc would
need to know to pass this switch, meaning it would need to know it had a
new assembler that knew about that switch.

Conversely, cpp under -lang-asm can start emitting .file and .line
directives instead of # lines.  However, the gas manual says that .file and
.line directives are only recognized for compatibility and might go away.
What's the story with that?  For cpp to get such a change, it would be
important to be sure that all past and future assemblers will grok it properly.


Thanks,
Roland

Re: gas debugging info vs cpp

[Zack Weinberg]

Roland McGrath <roland@redhat.com> writes:

> Conversely, cpp under -lang-asm can start emitting .file and .line
> directives instead of # lines.  However, the gas manual says that
> .file and .line directives are only recognized for compatibility and
> might go away.  What's the story with that?  For cpp to get such a
> change, it would be important to be sure that all past and future
> assemblers will grok it properly.

By the way, I'm happy to entertain changes to cpplib that would make
it more useful for preprocessing assembly language.  But you have to
tell me exactly what you need from it.

zw

Re: gas debugging info vs cpp

[Ian Lance Taylor]

Roland McGrath <roland@redhat.com> writes:

> So, I would like to fix this.  The question is, what needs to be fixed?
> The assembler can learn to grok cpp # lines, or cpp can learn to emit
> assembler .file/.line directives.  

The assembler should already recognize cpp # lines if '#' is in
line_comment_chars in the backend tc-*.c file.

What target are you using?

Ian

Re: gas debugging info vs cpp

[Roland McGrath]

> The assembler should already recognize cpp # lines if '#' is in
> line_comment_chars in the backend tc-*.c file.

Oops.  I was confused by reading the current source though using a build
from a while ago.  This was fixed by nick's 2003-01-29 change.
That's the best answer I could hope for!  Sorry about the misdirection.

> What target are you using?

i686-pc-linux-gnu


Thanks,
Roland