GDB Printers: Unintialized variable in gdb

[Ralf Habacker]

Am 24.08.21 um 17:27 schrieb Da Viper via Kde-finance-apps:
> But the Sigsegv exception is not a python exception 
> 
> I tried checking if the address is null but it's a valid address.
> 
> What I am try to mimick is something similar to the LLDB `SBValue.isValid()`
> 
> sbValue is similar to gdb.Value but for lldb
> 

The gdb counterpart is the class gdb.Value, which is returned by
gdb.parse_and_eval (expression)

    Parse expression, which must be a string, as an expression in the
current language, evaluate it, and return the result as a gdb.Value.

https://sourceware.org/gdb/onlinedocs/gdb/Basic-Python.html

To see if there is another way I used the following testcase, which
defines the pointer `b`, but points to an undefined memory address.

$cat << EOF > test-uninit.cpp
#include <stdio.h>

int main()
{
    int *a;
    int *b = (int*)0x12334;
    printf("%p %p\n", a, b);
}
EOF

$ gcc -o test-uninit test-uninit.cpp

$ cat << EOF > test-parse-and-eval.py
v = gdb.parse_and_eval('a')
print('a',v.dereference())

v = gdb.parse_and_eval('b')
#print('b',v.dereference())
try:
    print('b',v.dereference())
except:
    print('could not access')
EOF


$gdb test-uninit
(gdb)b 8
(gdb)r
(gdb)source test-parse-and-eval.py
 1
*b could not access

That seems to work for me.

Regards
Ralf