import gdb
import textwrap

class DisableBreakpoints:
    """
    Context-manager to temporarily disable all gdb breakpoints, useful if
    there is a risk to hit one during the evaluation of one of our custom
    commands
    """

    def __enter__(self):
        self.disabled_breakpoints = []
        for b in gdb.breakpoints():
            if b.enabled:
                b.enabled = False
                self.disabled_breakpoints.append(b)

    def __exit__(self, etype, evalue, tb):
        for b in self.disabled_breakpoints:
            b.enabled = True

class TensorRepr(gdb.Command):
    """
    Print a human readable representation of the given at::Tensor.
    Usage: torch-tensor-repr EXP

    at::Tensor instances do not have a C++ implementation of a repr method: in
    pytoch, this is done by pure-Python code. As such, torch-tensor-repr
    internally creates a Python wrapper for the given tensor and call repr()
    on it.
    """
    __doc__ = textwrap.dedent(__doc__).strip()

    def __init__(self):
        gdb.Command.__init__(self, 'torch-tensor-repr',
                             gdb.COMMAND_USER, gdb.COMPLETE_EXPRESSION)

    def invoke(self, args, from_tty):
        args = gdb.string_to_argv(args)
        if len(args) != 1:
            print('Usage: torch-tensor-repr EXP')
            return
        name = args[0]
        with DisableBreakpoints():
            res = gdb.parse_and_eval('torch::gdb::tensor_repr(%s)' % name)
            print('Python-level repr of %s:' % name)
            print(res.string())
            # torch::gdb::tensor_repr returns a malloc()ed buffer, let's free it
            gdb.parse_and_eval('(void)free(%s)' % int(res))

TensorRepr()