Variable read time * 3+ between program compiled w/ gcc 2.95 and w/ gcc 3.2 on Solaris

Eric Brunel
2003-04-24T14:39:01Z

Hi all,

I don't know if the following problem belongs here or in the gcc
newsgroup: we've noticed a drastic loss of performance when reading
program variables from gdb between the versions 2.95.3 and 3.2.2 of
gcc on Solaris 2.7. Here is a short example showing the problem:

--foo.cpp---------------
int x;

int main(int argc, char *argv[])
{
x = 12;
return 0;
}
------------------------

I then compile this program using g++ 2.95.3 and 3.2.2 into the
binaries foo2 and foo3 resp. Then I run:

gdb -batch -x gdb.cmds fooN

with the following commands file:

--gdb.cmds--------------
break foo.cpp:6
run
print x
print x
... (200 times)
print x
quit
-------------------------

Here are typical results:

$ time gdb -batch -x gdb.cmds foo2 > /dev/null

real 0m0.564s
user 0m0.150s
sys 0m0.110s

$ time gdb -batch -x gdb.cmds foo3 > /dev/null

real 0m1.726s
user 0m1.340s
sys 0m0.260s

The reading time has been increased by a factor 3+. This is even worse
if the variable is a structure and if I access fields in it. With a
chained list read via x->next->next->next..., we got times around
.5/.75 seconds with g++ 2.95, and more than 30 seconds (!) with g++
3.2

We tested versions 5.2 and 5.3 of gdb and got similar results.

Is this a bug? Is it known? Is there a workaround or a patch? Thanks a
lot in advance.
--
- Eric Brunel <eric.brunel@pragmadev.com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com