Does anyone use GDB on x86-solaris 2.7 or more recent?

Joel Brobecker
2002-04-05T16:21:59Z

Hello,

I'm chasing a problem that we are having with GDB on x86-solaris 2.6,
and it all goes down to the address stored by the assembler for static
symbols. I don't see this problem on sparc-solaris 2.8, which has a more
recent version of the assembler, so I am wondering if newer versions of
solaris distribute a more recent one, and if the problem is not fixed
when using this more recent assembler. I can't find some documentation
on the Sun website, so any feedback would be greatly appreciated.

Could anyone do the following for me? Assemble the attached assembly
file, and send me the object file. "gcc -c small.s" should do it. I'll
then check the address of the static symbol using objdump.

Here is a more detailed description of the problem. The problem was
originally with an Ada program, but I managed to reproduce it in C.

small.c:
<<
int
main (void)
{
struct fat_pointer
{
int lb0;
char *array;
};

static struct fat_pointer fp = { 0, 0};

if (fp.array == 0) {}
}
>>

The assembly file when compiled with -g looks like:
<<
fp.2:
.long 0
.long 0
.stabs "fp:V(0,20)",38,0,10,fp.2
>>

the variable "fp" is defined as a static variable, which is located at
fp.2. The problem is that the assembler seems to be storing the address
in the object file as an offset to the begining of the .data section
*for this file*. The real issue starts after the link is performed,
because the offset is not relative to the begining of the .data section
anymore, since the linker concatenates all .data sections one after the
other (and the linker did not perform any relocation on this stabs). As
a side comment, note that GDB currently expects an absolute address...

The relative adress can be observed using objdump --stabs:
<<
Symnum n_type n_othr n_desc n_value n_strx String
29 STSYM 0 10 00000000 952 fp:V(0,20)
^^^^^^^^
>>

And this causes the following error message in GDB:
<<
This GDB was configured as "i386-pc-solaris2.6"...
(gdb) b main
Breakpoint 1 at 0x80488e7: file small.c, line 12.
(gdb) run
Starting program: /lot.a/brobecke/gdb-testsuite/tests/6423-010/small

Breakpoint 1, main () at small.c:12
12 if (fp.array == 0) {}
(gdb) p fp
Cannot access memory at address 0x0
>>

I don't see any easy way of computing the address from the relative
offset. But since the assembler on sparc-solaris stores absolute
addresses, I was hoping that this problem would go away just by doing an
upgrade...

Thanks,
--
Joel