Problem with threaded program

[David Relson <relson@osagesoftware.com>]

Greetings,

The problem below was originally reported to the Linux Kernel Mailing 
List.  It looks to me to be a gdb problem.

I used a freshly compiled and installed copy of gdb-5.1 (configured as 
"i686-pc-linux-gnu") for this test on a Pentium III 500mhz running the 
2.4.16 kernel.  The same problem happens with gdb-5.0.  gdb-4.18 appears to 
work fine.

Here's the test program, test.c:

#include <stdlib.h>
int main() {
   char *t="1.0";
   double d=0;
   d=strtod(t,(char **)NULL);
   printf( "%f\n", d );
   return 0;
}

Build using "gcc -g -lpthread test.c"; run using "gdb a.out".

If you step through the program one line at a time and display variable d 
after each assignment, the strtod() call seems to return 
"nan(0x8000000000000)", which is also shown by print().

If you restart the program with a breakpoint at printf(), let it run, and 
display d at the breakpoint, the value shown is "1.000000" which is correct.

Is this a defect in gdb, or is my analysis wrong?

David

P.S.
--------------------------------------------------------
David Relson                   Osage Software Systems, Inc.
relson@osagesoftware.com       Ann Arbor, MI 48103
www.osagesoftware.com          tel:  734.821.8800