[gdb/python] Fix gdb.python/py-disasm.exp on arm-linux

After fixing test-case gdb.python/py-disasm.exp to recognize the arm nop:
...
	nop	{0}
...
we run into:
...
disassemble test^M
Dump of assembler code for function test:^M
   0x004004d8 <+0>:     push    {r11}           @ (str r11, [sp, #-4]!)^M
   0x004004dc <+4>:     add     r11, sp, #0^M
   0x004004e0 <+8>:     nop     {0}^M
=> 0x004004e4 <+12>:    Python Exception <class 'ValueError'>: Buffer \
  returned from read_memory is sized 0 instead of the expected 4^M
^M
unknown disassembler error (error = -1)^M
(gdb) FAIL: $exp: global_disassembler=ShowInfoRepr: disassemble test
...

This is caused by this code in gdbpy_disassembler::read_memory_func:
...
  gdbpy_ref<> result_obj (PyObject_CallMethod ((PyObject *) obj,
                                              "read_memory",
                                              "KL", len, offset));
...
where len has type "unsigned int", while "K" means "unsigned long long" [1].

Fix this by using "I" instead, meaning "unsigned int".

Also, offset has type LONGEST, which is typedef'ed to int64_t, while "L" means
"long long".

Fix this by using type gdb_py_longest for offset, in combination with format
character "GDB_PY_LL_ARG".  Likewise in disasmpy_info_read_memory.

Tested on arm-linux.

Reviewed-By: Alexandra Petlanova Hajkova <ahajkova@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>

PR python/31845
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31845

[1] https://docs.python.org/3/c-api/arg.html

gdb/python/py-disasm.c

@@ -667,12 +667,13 @@ disasmpy_info_read_memory (PyObject *self, PyObject *args, PyObject *kw)
   disasm_info_object *obj = (disasm_info_object *) self;
   DISASMPY_DISASM_INFO_REQUIRE_VALID (obj);
 
-  LONGEST length, offset = 0;
+  gdb_py_longest length, offset = 0;
   gdb::unique_xmalloc_ptr<gdb_byte> buffer;
   static const char *keywords[] = { "length", "offset", nullptr };
 
-  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "L|L", keywords,
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw,
-					&length, &offset))
+					GDB_PY_LL_ARG "|" GDB_PY_LL_ARG,
+					keywords, &length, &offset))
     return nullptr;
 
   /* The apparent address from which we are reading memory.  Note that in
@@ -849,13 +850,14 @@ gdbpy_disassembler::read_memory_func (bfd_vma memaddr, gdb_byte *buff,
   /* The DisassembleInfo.read_memory method expects an offset from the
      address stored within the DisassembleInfo object; calculate that
      offset here.  */
-  LONGEST offset = (LONGEST) memaddr - (LONGEST) obj->address;
+  gdb_py_longest offset
+    = (gdb_py_longest) memaddr - (gdb_py_longest) obj->address;
 
   /* Now call the DisassembleInfo.read_memory method.  This might have been
      overridden by the user.  */
   gdbpy_ref<> result_obj (PyObject_CallMethod ((PyObject *) obj,
 					       "read_memory",
-					       "KL", len, offset));
+					       "I" GDB_PY_LL_ARG, len, offset));
 
   /* Handle any exceptions.  */
   if (result_obj == nullptr)

gdb/testsuite/gdb.python/py-disasm.exp

@@ -65,7 +65,7 @@ proc py_remove_all_disassemblers {} {
 #
 # Each different disassembler tests some different feature of the
 # Python disassembler API.
-set nop "(nop|nop\t0)"
+set nop "(nop|nop\t0|[string_to_regexp nop\t{0}])"
 set unknown_error_pattern "unknown disassembler error \\(error = -1\\)"
 set addr_pattern "\r\n=> ${curr_pc_pattern} <\[^>\]+>:\\s+"
 set base_pattern "${addr_pattern}${nop}"

gdb/testsuite/gdb.python/py-disasm.py

@@ -46,7 +46,7 @@ def check_building_disassemble_result():
 
 
 def is_nop(s):
-    return s == "nop" or s == "nop\t0"
+    return s == "nop" or s == "nop\t0" or s == "nop\t{0}"
 
 
 # Remove all currently registered disassemblers.