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gdb/python: rework how the disassembler API reads the result object

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This commit is a refactor ahead of the next change which will make
disassembler styling available through the Python API.

Unfortunately, in order to make the styling support available, I think
the easiest solution is to make a very small change to the existing
API.

The current API relies on returning a DisassemblerResult object to
represent each disassembled instruction.  Currently GDB allows the
DisassemblerResult class to be sub-classed, which could mean that a
user tries to override the various attributes that exist on the
DisassemblerResult object.

This commit removes this ability, effectively making the
DisassemblerResult class final.

Though this is a change to the existing API, I'm hoping this isn't
going to cause too many issues:

  - The Python disassembler API was only added in the previous release
    of GDB, so I don't expect it to be widely used yet, and

  - It's not clear to me why a user would need to sub-class the
    DisassemblerResult type, I allowed it in the original patch
    because at the time I couldn't see any reason to NOT allow it.

Having prevented sub-classing I can now rework the tail end of the
gdbpy_print_insn function; instead of pulling the results out of the
DisassemblerResult object by calling back into Python, I now cast the
Python object back to its C++ type (disasm_result_object), and access
the fields directly from there.  In later commits I will be reworking
the disasm_result_object type in order to hold information about the
styled disassembler output.

The tests that dealt with sub-classing DisassemblerResult have been
removed, and a new test that confirms that DisassemblerResult can't be
sub-classed has been added.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Tom Tromey <tom@tromey.com>
This commit is contained in:
Andrew Burgess 2023-01-23 15:31:28 +00:00
parent 56c1f748a5
commit 0af2f23333
5 changed files with 30 additions and 79 deletions
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52
gdb/python/py-disasm.c
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@ -904,43 +904,14 @@ gdbpy_print_insn (struct gdbarch *gdbarch, CORE_ADDR memaddr,
return gdb::optional<int> (-1);
}
/* The call into Python neither raised an exception, or returned None.
Check to see if the result looks valid. */
gdbpy_ref<> length_obj (PyObject_GetAttrString (result.get (), "length"));
if (length_obj == nullptr)
{
gdbpy_print_stack ();
return gdb::optional<int> (-1);
}
gdbpy_ref<> string_obj (PyObject_GetAttrString (result.get (), "string"));
if (string_obj == nullptr)
{
gdbpy_print_stack ();
return gdb::optional<int> (-1);
}
if (!gdbpy_is_string (string_obj.get ()))
{
PyErr_SetString (PyExc_TypeError, _("String attribute is not a string."));
gdbpy_print_stack ();
return gdb::optional<int> (-1);
}
gdb::unique_xmalloc_ptr<char> string
= gdbpy_obj_to_string (string_obj.get ());
if (string == nullptr)
{
gdbpy_print_stack ();
return gdb::optional<int> (-1);
}
long length;
if (!gdb_py_int_as_long (length_obj.get (), &length))
{
gdbpy_print_stack ();
return gdb::optional<int> (-1);
}
/* The result from the Python disassembler has the correct type. Convert
this back to the underlying C++ object and read the state directly
from this object. */
struct disasm_result_object *result_obj
= (struct disasm_result_object *) result.get ();
/* Validate the length of the disassembled instruction. */
long length = result_obj->length;
long max_insn_length = (gdbarch_max_insn_length_p (gdbarch) ?
gdbarch_max_insn_length (gdbarch) : INT_MAX);
if (length <= 0)
@ -961,7 +932,10 @@ gdbpy_print_insn (struct gdbarch *gdbarch, CORE_ADDR memaddr,
return gdb::optional<int> (-1);
}
if (strlen (string.get ()) == 0)
/* Validate the text of the disassembled instruction. */
gdb_assert (result_obj->content != nullptr);
std::string string (std::move (result_obj->content->release ()));
if (strlen (string.c_str ()) == 0)
{
PyErr_SetString (PyExc_ValueError,
_("String attribute must not be empty."));
@ -971,7 +945,7 @@ gdbpy_print_insn (struct gdbarch *gdbarch, CORE_ADDR memaddr,
/* Print the disassembled instruction back to core GDB, and return the
length of the disassembled instruction. */
info->fprintf_func (info->stream, "%s", string.get ());
info->fprintf_func (info->stream, "%s", string.c_str ());
return gdb::optional<int> (length);
}
@ -1159,7 +1133,7 @@ PyTypeObject disasm_result_object_type = {
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
Py_TPFLAGS_DEFAULT, /*tp_flags*/
"GDB object, representing a disassembler result", /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */