From: frazer AT noneofyourbusiness DOT com (Scott Frazer)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Why can't GDB set a variable?
Date: Thu, 30 Jan 1997 01:07:21 GMT
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To: djgpp AT delorie DOT com
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jrubin AT bix DOT com (jrubin) wrote:

>GDB claims to be changing the value of the variable 'x',
>but the program doesn't seem to notice. When GDB exits,
>it reports failure to close the image file.


>File test.c:
>------------
>#include <stdio.h>

>int x = 1;

>int main(void)
>{
>  printf("test.c: x = %d\n",x);
>  return 0;
>}

>--------------
>gcc -g test.c
>gdb a.out
>(gdb) p x
>$1 = 1
>(gdb) set var x = 100
>(gdb) p x
>$2 = 100
>(gdb) r
>Starting program: c:/jsc/runtime/a.out
>test.c: x = 1
>(gdb) q
>warning: cannot close "c:/jsc/runtime/a.out": Permission denied (EACCES)

I think it's because you have not started the program yet.
I think initialized variables get set to their values when
you first start your program.  Here's what I got:

C:\TEST>gdb a.out
GDB is free software and you are welcome to distribute copies of it
 under certain conditions; type "show copying" to see the conditions.
There is absolutely no warranty for GDB; type "show warranty" for
details.
GDB 4.16 (go32), Copyright 1996 Free Software Foundation, Inc...
(gdb) hbreak main
Hardware assisted breakpoint 1 at 0x1568: file test.c, line 7.
(gdb) run
Starting program: c:/test/a.out

Breakpoint 1, main () at test.c:7
7         printf("test.c: x = %d\n",x);
(gdb) p x
$1 = 1
(gdb) set var x = 100
(gdb) continue
Continuing.
test.c: x = 100

Program exited normally.
0x10 in ?? ()
(gdb) q

C:\TEST>

BTW, I used a hardware break at main because I am running a
DOS window under Win 3.11, and regular breakpoints don't
work.

Hope this helps,
Scott