Cann't print local vars when nesting functions

Cann't print local vars when nesting functions

[Jeff]

I am having problems printing local stack variables when nesting 
functions. Here is a test app:
int main(int argc, char *argv[]){
  int i,j;
    i = 0;
    j = 1;
}

Now, run it to break on line:
    j = 1;
and then:
(gdb) p i
$2 = 0

and all is ok. but change to this:
int main(int argc, char *argv[]){
    int i,j;

    int inside(void){
       int k,l;
       k = 3;
       l = 4;
    }

    i = 0;
    j = 1;
}

Now set the break point to the same line, j =1, and this happens:
Breakpoint 1, main () at test.c:25
25        j = 1;
(gdb) p i
No symbol "i" in current context.
(gdb)

What gives? Is there something you need to special when nesting functions?

tj

Re: Cann't print local vars when nesting functions

[Eli Zaretskii]

> Date: Fri, 18 Feb 2005 17:54:17 -0500
> From: Jeff <wd4nmq@comcast.net>
> 
> int main(int argc, char *argv[]){
>     int i,j;
> 
>     int inside(void){
>        int k,l;
>        k = 3;
>        l = 4;
>     }
> 
>     i = 0;
>     j = 1;
> }
> 
> Now set the break point to the same line, j =1, and this happens:
> Breakpoint 1, main () at test.c:25
> 25        j = 1;
> (gdb) p i
> No symbol "i" in current context.
> (gdb)
> 
> What gives? Is there something you need to special when nesting functions?

Please tell the details: what platform is this, what versions of GCC
and GDB you use, and how (with what command-line options) you compiled
and linked the program.  Also, since the line "j = 1;" is not line 25
in the source you posted, could it be that the program you actually
compiled was different?

FWIW, I tried this with GCC 3.3.3, naive compiler command line, and
GDB 6.3, and couldn't reproduce the problem with the source you
posted.

Re: Cann't print local vars when nesting functions

[tj]

Eli Zaretskii wrote:

>>Date: Fri, 18 Feb 2005 17:54:17 -0500
>>From: Jeff <wd4nmq@comcast.net>
>>
>>int main(int argc, char *argv[]){
>>    int i,j;
>>
>>    int inside(void){
>>       int k,l;
>>       k = 3;
>>       l = 4;
>>    }
>>
>>    i = 0;
>>    j = 1;
>>}
>>
>>Now set the break point to the same line, j =1, and this happens:
>>Breakpoint 1, main () at test.c:25
>>25        j = 1;
>>(gdb) p i
>>No symbol "i" in current context.
>>(gdb)
>>
>>What gives? Is there something you need to special when nesting functions?
>>    
>>
>
>Please tell the details: what platform is this, what versions of GCC
>and GDB you use, and how (with what command-line options) you compiled
>and linked the program.  Also, since the line "j = 1;" is not line 25
>in the source you posted, could it be that the program you actually
>compiled was different?
>
>FWIW, I tried this with GCC 3.3.3, naive compiler command line, and
>GDB 6.3, and couldn't reproduce the problem with the source you
>posted.
>
>  
>
I am on linux, 2.4.26 kernel
gcc 3.2.3
gdb 5.3
Source file test.c:
#include <stdio.h>

int main(int argc, char *argv[]){

  int i,j;
  int inside(void){
    int k,l;

    k = 1;
    l = k;
    return 0;

  }

  i = 0;
  j = 1;
}

test$ cc -g -O0 test.c
$ gdb ./a.out
GNU gdb 5.3
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or 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.
This GDB was configured as "i386-slackware-linux"...
(gdb) b test.c:16
Breakpoint 1 at 0x8048340: file test.c, line 16.
(gdb) run
Starting program: test/a.out

Breakpoint 1, main () at test.c:16
16        j = 1;
(gdb) p i
No symbol "i" in current context.
(gdb)

As stated, removing the inside() function, breaking on the same source 
line and printing causes i's value to be printed. No error message.

tj

Re: Cann't print local vars when nesting functions

[Eli Zaretskii]

> Date: Sat, 19 Feb 2005 11:25:39 -0500
> From: tj <999alfred@comcast.net>
> CC: gdb@sources.redhat.com
> 
> I am on linux, 2.4.26 kernel
> gcc 3.2.3
> gdb 5.3
> Source file test.c:
> #include <stdio.h>
> 
> int main(int argc, char *argv[]){
> 
>   int i,j;
>   int inside(void){
>     int k,l;
> 
>     k = 1;
>     l = k;
>     return 0;
> 
>   }
> 
>   i = 0;
>   j = 1;
> }
> 
> test$ cc -g -O0 test.c
> $ gdb ./a.out
> GNU gdb 5.3
> Copyright 2002 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you are
> welcome to change it and/or 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.
> This GDB was configured as "i386-slackware-linux"...
> (gdb) b test.c:16
> Breakpoint 1 at 0x8048340: file test.c, line 16.
> (gdb) run
> Starting program: test/a.out
> 
> Breakpoint 1, main () at test.c:16
> 16        j = 1;
> (gdb) p i
> No symbol "i" in current context.
> (gdb)

Well, all I can say that with GDB 6.1 and 6.3 I don't see this
problem.  Unless someone who knows more than I do about problems
specific to GNU/Linux, I'd suggest to upgrade to newer versions of GCC
and GDB, and see if the problem goes away.

Re: Cann't print local vars when nesting functions

[tj]

Eli Zaretskii wrote:

>>Date: Sat, 19 Feb 2005 11:25:39 -0500
>>From: tj <999alfred@comcast.net>
>>CC: gdb@sources.redhat.com
>>
>>I am on linux, 2.4.26 kernel
>>gcc 3.2.3
>>gdb 5.3
>>Source file test.c:
>>#include <stdio.h>
>>
>>int main(int argc, char *argv[]){
>>
>>  int i,j;
>>  int inside(void){
>>    int k,l;
>>
>>    k = 1;
>>    l = k;
>>    return 0;
>>
>>  }
>>
>>  i = 0;
>>  j = 1;
>>}
>>
>>test$ cc -g -O0 test.c
>>$ gdb ./a.out
>>GNU gdb 5.3
>>Copyright 2002 Free Software Foundation, Inc.
>>GDB is free software, covered by the GNU General Public License, and you are
>>welcome to change it and/or 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.
>>This GDB was configured as "i386-slackware-linux"...
>>(gdb) b test.c:16
>>Breakpoint 1 at 0x8048340: file test.c, line 16.
>>(gdb) run
>>Starting program: test/a.out
>>
>>Breakpoint 1, main () at test.c:16
>>16        j = 1;
>>(gdb) p i
>>No symbol "i" in current context.
>>(gdb)
>>    
>>
>
>Well, all I can say that with GDB 6.1 and 6.3 I don't see this
>problem.  Unless someone who knows more than I do about problems
>specific to GNU/Linux, I'd suggest to upgrade to newer versions of GCC
>and GDB, and see if the problem goes away.
>
>  
>
Your right. My system was built from Slackware 9.1. I ssh'ed to a 
buddy's machine that was built using Slackware 10.0. It has gcc v3.3.4 
and gdb 6.1.1. I now display the values and no "not in present context 
messages".
Oh well, wonder why it took so long for that to get fixed/included?

Well, guess I need to update my system, heavy sigh.

Thank you for getting me pointed in the right direction.

tj