从 Python 方便 function 返回空字符串“”而不是 0x0

Question

Returning the Python string "" from a gdb convenience function 's invoke method appears to produce a result of 0x0 instead of the expected "" .

This is because gdb.Value("") yields 0x0 :

(gdb) python
>print(gdb.Value(""))
>end
0x0

which is what'll happen when a Python string is returned.

Is there any sensible way to get gdb to yield a gdb.Value for a char[] or char* that points to \x00 , ie the string "" ?

Answer 1

It certainly isn't a good way, but the workaround I'm using for now is to construct my own raw gdb.Value from a buffer where I explicitly supply a char[] type (python3):

(gdb) python print( gdb.Value(b'\x00', gdb.lookup_type('char').array(0) ) )
""

eg a gdb convenience function:

class Indent(gdb.Function):
    """Generate a string of 'depth' spaces"""

    def __init__(self):
        super(Indent, self).__init__("indent")

    def invoke(self, depth):
        """https://stackoverflow.com/a/66757722/398670"""
        depth = int(depth)
        if (depth <= 0):
            return gdb.Value(b"\x00", gdb.lookup_type('char').array(0))
        else:
            return " " * int(depth)

Indent()

But surely this can't be the right way, so I'm hoping someone will come along with a better solution.