with-gdb gives you a backtrace and an interactive gdb if your program segfaults:

$ ./segfaulty
1
2
3
Segmentation fault

$ eval `/path/to/with-gdb/with-gdb`
$ ./segfaulty
1
2
3
[... some gdb spam ...]
Program received signal SIGSEGV, Segmentation fault.
0x0000000000400591 in bad_function () at segfaulty.c:3
3	int bad_function() { return *p; }
#0  0x0000000000400591 in bad_function () at segfaulty.c:3
#1  0x00000000004005bc in main () at segfaulty.c:5
(gdb)

it's entirely useless, because your programs never segfault.

with-gdb doesn't run programs under gdb - that affects performance and sometimes semantics. instead, it adds a signal handler to every program: if they receive SIGSEGV or SIGABRT, a gdb instance is started and attached to the failing process.