Re: [PATCH/RFC] faster language identification

[Jim Blandy <jimb at redhat dot com>]

Daniel Jacobowitz <drow@mvista.com> writes:
> On Sun, Nov 10, 2002 at 05:01:25PM +0200, Elias Athanasopoulos wrote:
> > Hi Michael,
> > 
> > On Thu, Nov 07, 2002 at 12:55:47PM -0800, Michael Snyder wrote:
> > > Elias Athanasopoulos wrote:
> > > > On Thu, Nov 07, 2002 at 02:48:38PM -0500, Daniel Jacobowitz wrote:
> > > > > No, the patch converts the psymtab to a symtab and uses the language in
> > > > > the symtab.  That's what I want you NOT to do.  psymtab_to_symtab is
> > > > > expensive!
> > > Perhaps the patch could be added to psymtab_to_symtab, 
> > > so that it would not try to get the language until 
> > > the symbols were going to be read anyway?
> > 
> > Yes, that may work, although I don't know exactly where gdb *really* needs
> > to set the language.
> > 
> > I was thinking of what Daniel proposed; a psymtab_language() function. But,
> > even in the DWARF case, consider this:
> > 
> > % gcc -Wa,-gdwarf2 bar.s foo.c -o foo
> > 
> > Now, the language should be set to 'asm'? This is what you'll get if you try
> > to parse the .debug_info section. Currently, gdb in the above case sets it
> > to 'c'.
> > 
> > Also, there is the case that you enable DWARF in both as and gcc, but I think
> > this shouldn't be allowed by gcc.
> 
> Well, it _should_ be asm.  We don't have line number information for
> the .c source.  IMHO.
> 
> (Also IMHO, the user just shouldn't do that...)

Shouldn't do what?  Compile assembly with debug info?  Link object
modules with a mix of debuggingness?  I don't see what's wrong...

The right behavior here, it seems to me, depends on which module
contains 'main'.  If that module has debug info, we should use that to
choose the initial language; otherwise, we can guess from the source
filename.  Even .c files compiled without debugging info have a .file
directive in the assembly code, which turns into an STT_FILE linker
symbol.