Re: PATCH: PR gas/10531: Strange assembler warning message on section group

[Jim Wilson <wilson at codesourcery dot com>]

On Tue, 2009-08-18 at 20:08 -0700, H.J. Lu wrote:
> The main problem is we shouldn't identify a section just by section name only.

I don't think that you understand the complete problem here.  This patch
will make the spurious warning message go away.  This does not solve the
problem that gas is emitting bogus debug info into a file that already
contains debug info.

This is trivial to prove with a small example.  Put this into a C file
int main (void) { asm (""); return 0; }
Compile with "icc -c -g".  Run "readelf -wl" on the .o file, and you
will see that we have two directory tables, two file name tables, two
line number tables, etc.  The first set is OK, and was emitted by icc.
The second set is bogus, and was emitted by gas.

The reason that an unpatched gas can emit a bogus warning is that when
we have comdat sections, gas accidentally emits the bogus debug info
into a comdat section, corrupting the comdat section.  Your patch fixes
this by emitting the bogus debug info into a regular section.  This is
good, and necessary, but we are still emitting bogus debug info with
your patch.  I think this needs to be fixed also.  We can probably fix
this with a separate patch.

If you want an example that generates the bogus warning, then try this
inline int sub (void) { return 0; }
int main (void) { asm (""); return sub (); }
When I compile with "icc -O -g -c" I get a bogus warning.  And running
"readelf -wl" on the output shows again that we have bogus debug info
emitted by gas, except now it is in a comdat section.

Jim