how@IVY.UCDAVIS.EDU (W. Wilson Ho) (09/16/89)
Consider the following one line program:
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how@ivy:55> cat test.c
main () {printf ("hello world \n");}
how@ivy:56> gcc -g test.c
how@ivy:57> gdb a.out
GDB 3.2, Copyright (C) 1988 Free Software Foundation, Inc.
There is ABSOLUTELY NO WARRANTY for GDB; type "info warranty" for details.
GDB is free software and you are welcome to distribute copies of it
under certain conditions; type "info copying" to see the conditions.
Reading symbol data from /usr/home/how/work/a.out...done.
Type "help" for a list of commands.
(gdb) list
Reading in symbols for test.c...done.
1 main () {printf ("hello world \n");}
(gdb) b main
Breakpoint 1 at 0x20c0: file test.c, line 1.
(gdb) run
Starting program: /usr/home/how/work/a.out
Bpt 1, 0x20c0 in mswitchfp_ ()
(gdb) step
Current function has no line number information.
Single stepping until function exit.
0x20d8 in mswitchfp_ ()
(gdb) step
Current function has no line number information.
Single stepping until function exit.
0x2046 in start ()
(gdb) cont
Continuing.
hello world
Program exited normally.
(gdb) quit
how@ivy:58>
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Obviously gdb loses track of relationship between the line
number in the source file and the actual memory address in the
inferior process.
The error happens on both Sun's and Vaxes. But dbx handles
this correctly.
However, only for the Sun's, if I compile the program with
/bin/cc, both gdb and dbx work correctly.
When I rewrite the program by splitting it into several lines,
gdb works ok:
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how@ivy:59> cat test.c
main () {
printf ("hello world \n");
}
how@ivy:60> gcc -g test.c
how@ivy:61> gdb a.out
GDB 3.2, Copyright (C) 1988 Free Software Foundation, Inc.
There is ABSOLUTELY NO WARRANTY for GDB; type "info warranty" for details.
GDB is free software and you are welcome to distribute copies of it
under certain conditions; type "info copying" to see the conditions.
Reading symbol data from /usr/home/how/work/a.out...done.
Type "help" for a list of commands.
(gdb) list
Reading in symbols for test.c...done.
1 main () {
2 printf ("hello world \n");
3 }
(gdb) b main
Breakpoint 1 at 0x20b2: file test.c, line 2.
(gdb) r
Starting program: /usr/home/how/work/a.out
Bpt 1, main () (test.c line 2)
2 printf ("hello world \n");
(gdb) s
hello world
3 }
(gdb) s
0x20be in main () (test.c line 3)
3 }
(gdb) cont
Continuing.
Program exited normally.
(gdb) quit
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It seems that either gcc is not generating the correct
debugging symbol table information, or there is a bug in gdb.
Wilson Ho