[vox-tech] bug in gdb?

[Rod Roark]

Try this.  :-)

#!/usr/bin/perl
sub bob() { (@_[0] > 0 ? @_[0] : "no") . " bottle" . (@_[0] =3D=3D 1 ? ""=
 : "s") . " of beer" }
my $s =3D "s";
my $bob =3D " bottle$s of beer";
my $wall =3D " on the wall\n";
my $fall =3D "\nIf one of those bottles should happen to fall\nThere'll b=
e ";
my $i =3D 99;
print &bob($i), $wall, &bob($i), $fall, &bob(--$i), $wall, "\n" while ($i=
 > 0);

-- Rod
   http://www.sunsetsystems.com/

On Friday 20 September 2002 05:52 pm, Peter Jay Salzman wrote:
> gdb isn't doing something i'm expecting it to do.  i'm wondering if thi=
s
> is a bug or feature.
>
> here's the code:
>
>    int main(void)
>    {
>       int i =3D 5;
>
>       while (i)
>          --i;
>
>       return 0;
>    }
>
>
> my goal is to teach gdb how to sing the "bottles of beer" song.
>
> here are the commands.  blank lines indicate that gdb is singing, so
> there will be output.  you can cut and paste this into a gdb session,
> but cut and paste it in blocks (so do the 1st block first, let gdb run,
> then repeat for the 2nd and 3rd blocks).
>
> note, breakpoint 1 is set simply to let the variable "i" come into
> scope.  after that, i don't need it anymore so i delete breakpoint 1.
>
>
> break main
> run
> break 6
> commands 2
> printf "%d bottles of beer on the wall, %d bottles of beer.\n", i, i
> printf "If one of those bottles happen to fall...\n"
> end
> continue
>
>
> commands 2
> silent
> printf "%d bottles of beer on the wall, %d bottles of beer.\n", i, i
> printf "If one of those bottles happen to fall...\n"
> continue
> end
> delete 1
> run
>
>
> break 6 if i < 5
> commands 3
> silent
> printf "%d bottles of beer on the wall!\n", i - 1
> continue
> end
> run
>
>
> if you think about it, i didn't do things quite efficiently.  the reaso=
n
> for this is that this is part of a tutorial i'm writing.  but it should
> still work.
>
> after the last "run", here's the output:
>
>   (gdb) run
>   5 bottles of beer on the wall, 5 bottles of beer.
>   If one of those bottles happen to fall...
>   4 bottles of beer on the wall, 4 bottles of beer.
>   If one of those bottles happen to fall...
>   3 bottles of beer on the wall, 3 bottles of beer.
>   If one of those bottles happen to fall...
>   2 bottles of beer on the wall, 2 bottles of beer.
>   If one of those bottles happen to fall...
>   1 bottles of beer on the wall, 1 bottles of beer.
>   If one of those bottles happen to fall...
>
> the problem is that breakpoint #3 isn't printing anything:
>
>   (gdb) i b
>   Num Type           Disp Enb Address    What
>   2   breakpoint     keep y   0x080483d8 in main at sing.c:6
>           breakpoint already hit 5 times
>           silent
>           printf "%d bottles of beer on the wall, %d bottles of beer.\n=
",
> i, i printf "If one of those bottles happen to fall...\n"
>           continue
>   3   breakpoint     keep y   0x080483d8 in main at sing.c:6
>           stop only if i < 5
>           breakpoint already hit 4 times
>           silent
>           printf "%d bottle of beer on the wall!\n", i - 1
>           continue
>
> what if i delete the 2nd breakpoint:
>
>    (gdb) disable 2
>    (gdb) run
>    Starting program: /home/p/writing/ddd/src/sing
>    3 bottle of beer on the wall!
>    2 bottle of beer on the wall!
>    1 bottle of beer on the wall!
>    0 bottle of beer on the wall!
>
> looks ok, but i'm not sure why i=3D4 isn't being printed.  anyway, now
> i'll re-enable the 2nd breakpoint:
>
>    (gdb) enable 2
>    (gdb) run
>    Starting program: /home/p/writing/ddd/src/sing
>    5 bottles of beer on the wall, 5 bottles of beer.
>    If one of those bottles happen to fall...
>    4 bottles of beer on the wall, 4 bottles of beer.
>    If one of those bottles happen to fall...
>    3 bottles of beer on the wall, 3 bottles of beer.
>    If one of those bottles happen to fall...
>    2 bottles of beer on the wall, 2 bottles of beer.
>    If one of those bottles happen to fall...
>    1 bottles of beer on the wall, 1 bottles of beer.
>    If one of those bottles happen to fall...
>
> once the 2nd breakpoint is enabled, the 3rd breakpoint doesn't print
> anything.   however, as you can see, the 3rd breakpoint was hit 4 times=
=2E
>
>
> i can't find anything in the user manual that talks about command lists
> for breakpoints set on top of each other.
>
> is this a bug or am i missing something?
>
> pete