Error while debugging in Fedora

[lang_tu]

I just wrote a simple Hello world program in C (my Linux distro is Fedora 5) and it ran well when built: gcc -g hello.c -o hello .
But when I try to debug it as follow

debug hello
set args a b c
b 4 
show args // a b c
r
p argc // Error !!!???

Is that an error of Fedora 5 's gdb ?

[wje_lf]

I'm having a difficult time making sense of some of your gdb commands.

1. If your hello world program is small, please post the complete program source.
2. Please post the command you used to compile the program.
3. Please post the exact error message you got from gdb.

[lang_tu]

Sorry,here is the source

#include<stdio.h>
int main()
{
       printf("Hello world");
       return 0;
}

That's all.
And the error message is
Cannot access memory at address 0x0

[wje_lf]

I'm using Slackware 9.1, not Fedora, but when I run this script:

#!/bin/bash

cat > hello.c <<EOD
#include<stdio.h>
int main()
{
       printf("Hello world");
       return 0;
}
EOD
gcc -Wall -g hello.c -o hello
cat > gdb_commands <<EOD
set args a b c
b 4
r
p argc
EOD
gdb -n -x gdb_commands hello

I get this as output:

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"...
Breakpoint 1 at 0x804834c: file hello.c, line 4.

Breakpoint 1, main () at hello.c:4
4              printf("Hello world");
gdb_commands:4: Error in sourced command file:
No symbol "argc" in current context.
(gdb)

but when I run this script:

#include<stdio.h>
int main(int argc, char **argv)
{
       printf("Hello world");
       return 0;
}
EOD
gcc -Wall -g hello.c -o hello
cat > gdb_commands <<EOD
set args a b c
b 4
r
p argc
EOD
gdb -n -x gdb_commands hello

I get this output:

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"...
Breakpoint 1 at 0x804834c: file hello.c, line 4.

Breakpoint 1, main (argc=4, argv=0xbffff9a4) at hello.c:4
4              printf("Hello world");
$1 = 4
(gdb)

Hope this helps.

[lang_tu]

Omg,I forgot to type the int argc,char ** argv . In my source code , I did have those !!! I just forgot when posting here !
And besides,the error message is "cannot access memory at 0x0" (not "no .. in current context").
I must emphasize that I use Fedora 5 , and it leads to this error .
At my school,the version is FC 2 and I debugged(exactly these commands) well (just like you !)
I think the problem is FC 5 . It may seem weird to blame for the distro , but if someone is using FC 5,could you test it for me ?

[wje_lf]

So what happens when you copy and paste the following into a file, chmod that file to 700, and run it? Can you take the exact output from that and paste it into a reply to this thread?

#!/bin/bash

cat > hello.c <<EOD
#include<stdio.h>
int main(int argc, char **argv)
{
       printf("Hello world");
       return 0;
}
EOD
gcc -Wall -g hello.c -o hello
cat > gdb_commands <<EOD
set args a b c
b 4
r
p argc
EOD
gdb -n -x gdb_commands hello

[lang_tu]

Here is the output

 ./bame
GNU gdb Red Hat Linux (6.3.0.0-1.134.fc5rh)
Copyright 2004 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-redhat-linux-gnu"...Using host libthread_db library "/lib/libthread_db.so.1".

Breakpoint 1 at 0x8048395: file hello.c, line 4.

Breakpoint 1, main () at hello.c:4
4              printf("Hello world");
gdb_commands:4: Error in sourced command file:
Cannot access memory at address 0x0
(gdb)

[wje_lf]

That's funny. If I wanted to see output like that, I'd have to run a script something like this:

#!/bin/bash

cat > hello.c <<EOD
#include<stdio.h>
int main(int argc, char **argv)
{
       printf("Hello world");
       return 0;
}
EOD
gcc -Wall -g hello.c -o hello
cat > gdb_commands <<EOD
set args a b c
b 4
r
p *argv[argc]
EOD
gdb -n -x gdb_commands hello

which for obvious reasons gives me:

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"...
Breakpoint 1 at 0x804834c: file hello.c, line 4.

Breakpoint 1, main (argc=4, argv=0xbffff9a4) at hello.c:4
4              printf("Hello world");
gdb_commands:4: Error in sourced command file:
Cannot access memory at address 0x0
(gdb)

I don't have the foggiest notion why you got the error you got with my previous script. I'm hoping someone else can jump in here.

[lang_tu]

Can someone help me plz

[wje_lf]

Can someone help me plz

If you ran the script I offered in post 6, and that script was running a stock (unmodified) compiler and assembler and linker and debugger, and you got the output you describe in post 7, then I'm going to go out on a limb here and say that there is something seriously wrong with your system.