Re: [gentoo-dev] Re: Split ELF Debug (default or not?)

[Ned Ludd]

On Sun, 2005-11-27 at 15:22 +0000, Edward Catmur wrote:
> On Sun, 2005-11-27 at 08:40 -0500, Ned Ludd wrote:
> > On Sun, 2005-11-27 at 15:09 +0200, Ivan Yosifov wrote:
> > > And one more thing. For proper debugging, don't I need the source to be
> > > present ?
> >
> > -g3 -ggdb embeds the source code in the debug info so I don't see the
> > point.
>
> It doesn't; at least not with gcc 3.4.4. It does embed function
> prototypes and macro definitions, though.
>
> Ed Catmur

Eh? 


solar@simple ~ $ gcc -g3 -nopie -ggdb segfault_me.c -o segfault_me
solar@simple ~ $ paxctl -permsx segfault_me
solar@simple ~ $ gdb -q ./segfault_me
Using host libthread_db library "/lib/libthread_db.so.1".
(gdb) b main
Breakpoint 1 at 0x804853d: file segfault_me.c, line 25.
(gdb) step
The program is not being run.
(gdb) r
Starting program: /home/solar/segfault_me 

Breakpoint 1, main () at segfault_me.c:25
25		foo();
(gdb) step
foo () at segfault_me.c:17
17		int i = 0; 
(gdb) 
18		for (i = 0 ; i < 3; i++) {
(gdb) 
19			printf("Just an example %d\n", i);
(gdb) 
Just an example 0
18		for (i = 0 ; i < 3; i++) {
(gdb) 
19			printf("Just an example %d\n", i);
(gdb) 
Just an example 1
18		for (i = 0 ; i < 3; i++) {
(gdb) 
19			printf("Just an example %d\n", i);
(gdb) 
Just an example 2
18		for (i = 0 ; i < 3; i++) {
(gdb) 
21		bar();
(gdb) 
bar () at segfault_me.c:13
13		baz();
(gdb) 
baz () at segfault_me.c:9
9		atexit(break_self);
(gdb) 
10	}
(gdb) 
bar () at segfault_me.c:14
14	}
(gdb) 
foo () at segfault_me.c:22
22	}
(gdb) 
main () at segfault_me.c:26
26		return 0;
(gdb) 
27	}
(gdb) 
0x400407b6 in __libc_start_main () from /lib/libc.so.6
(gdb) 
Single stepping until exit from function __libc_start_main, 
which has no line number information.

Program received signal SIGSEGV, Segmentation fault.
0x40050681 in kill () from /lib/libc.so.6
(gdb) 

solar@simple ~ $ cat segfault_me.c 
#include <stdio.h>
#include <signal.h>

void break_self() {
	kill(getpid(), SIGSEGV);
}

int baz() {
	atexit(break_self);
}

void bar() {
	baz();
}

void foo() {
	int i; 
	for (i = 0 ; i < 3; i++) {
		printf("Just an example %d\n", i);
	}
	bar();
}

int main() {
	foo();
	return 0;
}



# While single stepping sure looks like source code to me. 

solar@simple ~ $ gcc -v 2>&1 | tail -n 1
gcc version 3.4.4 (Gentoo Hardened 3.4.4, HTB-3.4.4_pre-1.00,
ssp-3.4.4-1.0, pie-8.7.8)

-- 
Ned Ludd <solar@g.o>
Gentoo Linux

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