1 # Python hooks for gdb for debugging GCC
2 # Copyright (C) 2013-2018 Free Software Foundation, Inc.
4 # Contributed by David Malcolm <dmalcolm@redhat.com>
6 # This file is part of GCC.
8 # GCC is free software; you can redistribute it and/or modify it under
9 # the terms of the GNU General Public License as published by the Free
10 # Software Foundation; either version 3, or (at your option) any later
13 # GCC is distributed in the hope that it will be useful, but WITHOUT
14 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 # You should have received a copy of the GNU General Public License
19 # along with GCC; see the file COPYING3. If not see
20 # <http://www.gnu.org/licenses/>.
23 Enabling the debugging hooks
24 ----------------------------
25 gcc/configure (from configure.ac) generates a .gdbinit within the "gcc"
26 subdirectory of the build directory, and when run by gdb, this imports
27 gcc/gdbhooks.py from the source directory, injecting useful Python code
30 You may see a message from gdb of the form:
31 "path-to-build/gcc/.gdbinit" auto-loading has been declined by your `auto-load safe-path'
32 as a protection against untrustworthy python scripts. See
33 http://sourceware.org/gdb/onlinedocs/gdb/Auto_002dloading-safe-path.html
35 The fix is to mark the paths of the build/gcc directory as trustworthy.
36 An easy way to do so is by adding the following to your ~/.gdbinit script:
37 add-auto-load-safe-path /absolute/path/to/build/gcc
38 for the build directories for your various checkouts of gcc.
40 If it's working, you should see the message:
41 Successfully loaded GDB hooks for GCC
44 During development, I've been manually invoking the code in this way, as a
45 precanned way of printing a variety of different kinds of value:
48 -ex "break expand_gimple_stmt" \
54 Examples of output using the pretty-printers
55 --------------------------------------------
56 Pointer values are generally shown in the form:
57 <type address extra_info>
59 For example, an opt_pass* might appear as:
61 $2 = <opt_pass* 0x188b600 "expand"(170)>
63 The name of the pass is given ("expand"), together with the
66 Note that you can dereference the pointer in the normal way:
68 $4 = {type = RTL_PASS, name = 0x120a312 "expand",
71 and you can suppress pretty-printers using /r (for "raw"):
73 $3 = (opt_pass *) 0x188b600
75 Basic blocks are shown with their index in parentheses, apart from the
76 CFG's entry and exit blocks, which are given as "ENTRY" and "EXIT":
78 $9 = <basic_block 0x7ffff041f1a0 (2)>
79 (gdb) p cfun->cfg->x_entry_block_ptr
80 $10 = <basic_block 0x7ffff041f0d0 (ENTRY)>
81 (gdb) p cfun->cfg->x_exit_block_ptr
82 $11 = <basic_block 0x7ffff041f138 (EXIT)>
84 CFG edges are shown with the src and dest blocks given in parentheses:
86 $1 = <edge 0x7ffff043f118 (ENTRY -> 6)>
88 Tree nodes are printed using Python code that emulates print_node_brief,
89 running in gdb, rather than in the inferior:
91 $1 = <function_decl 0x7ffff0420b00 foo>
92 For usability, the type is printed first (e.g. "function_decl"), rather
95 RTL expressions use a kludge: they are pretty-printed by injecting
96 calls into print-rtl.c into the inferior:
97 Value returned is $1 = (note 9 8 10 [bb 3] NOTE_INSN_BASIC_BLOCK)
99 $2 = (note 9 8 10 [bb 3] NOTE_INSN_BASIC_BLOCK)
101 $3 = (rtx_def *) 0x7ffff043e140
102 This won't work for coredumps, and probably in other circumstances, but
103 it's a quick way of getting lots of debuggability quickly.
105 Callgraph nodes are printed with the name of the function decl, if
108 #5 0x00000000006c288a in expand_function (node=<cgraph_node* 0x7ffff0312720 "foo">) at ../../src/gcc/cgraphunit.c:1594
109 1594 execute_pass_list (g->get_passes ()->all_passes);
111 $1 = <cgraph_node* 0x7ffff0312720 "foo">
113 vec<> pointers are printed as the address followed by the elements in
114 braces. Here's a length 2 vec:
116 $18 = 0x7ffff0428b68 = {<edge 0x7ffff044d380 (3 -> 5)>, <edge 0x7ffff044d3b8 (4 -> 5)>}
118 and here's a length 1 vec:
120 $19 = 0x7ffff0428bb8 = {<edge 0x7ffff044d3f0 (5 -> EXIT)>}
122 You cannot yet use array notation [] to access the elements within the
123 vector: attempting to do so instead gives you the vec itself (for vec[0]),
124 or a (probably) invalid cast to vec<> for the memory after the vec (for
127 Instead (for now) you must access m_vecdata:
128 (gdb) p bb->preds->m_vecdata[0]
129 $20 = <edge 0x7ffff044d380 (3 -> 5)>
130 (gdb) p bb->preds->m_vecdata[1]
131 $21 = <edge 0x7ffff044d3b8 (4 -> 5)>
142 # Convert "enum tree_code" (tree.def and tree.h) to a dict:
143 tree_code_dict = gdb.types.make_enum_dict(gdb.lookup_type('enum tree_code'))
145 # ...and look up specific values for use later:
146 IDENTIFIER_NODE = tree_code_dict['IDENTIFIER_NODE']
147 TYPE_DECL = tree_code_dict['TYPE_DECL']
149 # Similarly for "enum tree_code_class" (tree.h):
150 tree_code_class_dict = gdb.types.make_enum_dict(gdb.lookup_type('enum tree_code_class'))
151 tcc_type = tree_code_class_dict['tcc_type']
152 tcc_declaration = tree_code_class_dict['tcc_declaration']
154 # Python3 has int() with arbitrary precision (bignum). Python2 int() is 32-bit
155 # on 32-bit hosts but remote targets may have 64-bit pointers there; Python2
156 # long() is always 64-bit but Python3 no longer has anything named long.
158 return long(gdbval) if sys.version_info.major == 2 else int(gdbval)
162 Wrapper around a gdb.Value for a tree, with various methods
163 corresponding to macros in gcc/tree.h
165 def __init__(self, gdbval):
168 def is_nonnull(self):
169 return intptr(self.gdbval)
173 Get gdb.Value corresponding to TREE_CODE (self)
175 #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
177 return self.gdbval['base']['code']
181 Get Tree instance corresponding to DECL_NAME (self)
183 return Tree(self.gdbval['decl_minimal']['name'])
187 Get Tree instance corresponding to result of TYPE_NAME (self)
189 return Tree(self.gdbval['type_common']['name'])
191 def IDENTIFIER_POINTER(self):
193 Get str correspoinding to result of IDENTIFIER_NODE (self)
195 return self.gdbval['identifier']['id']['str'].string()
200 def __init__ (self, gdbval):
202 self.node = Tree(gdbval)
204 def to_string (self):
205 # like gcc/print-tree.c:print_node_brief
206 # #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
207 # tree_code_name[(int) TREE_CODE (node)])
208 if intptr(self.gdbval) == 0:
211 val_TREE_CODE = self.node.TREE_CODE()
213 # extern const enum tree_code_class tree_code_type[];
214 # #define TREE_CODE_CLASS(CODE) tree_code_type[(int) (CODE)]
216 val_tree_code_type = gdb.parse_and_eval('tree_code_type')
217 val_tclass = val_tree_code_type[val_TREE_CODE]
219 val_tree_code_name = gdb.parse_and_eval('tree_code_name')
220 val_code_name = val_tree_code_name[intptr(val_TREE_CODE)]
221 #print(val_code_name.string())
223 result = '<%s 0x%x' % (val_code_name.string(), intptr(self.gdbval))
224 if intptr(val_tclass) == tcc_declaration:
225 tree_DECL_NAME = self.node.DECL_NAME()
226 if tree_DECL_NAME.is_nonnull():
227 result += ' %s' % tree_DECL_NAME.IDENTIFIER_POINTER()
229 pass # TODO: labels etc
230 elif intptr(val_tclass) == tcc_type:
231 tree_TYPE_NAME = Tree(self.gdbval['type_common']['name'])
232 if tree_TYPE_NAME.is_nonnull():
233 if tree_TYPE_NAME.TREE_CODE() == IDENTIFIER_NODE:
234 result += ' %s' % tree_TYPE_NAME.IDENTIFIER_POINTER()
235 elif tree_TYPE_NAME.TREE_CODE() == TYPE_DECL:
236 if tree_TYPE_NAME.DECL_NAME().is_nonnull():
237 result += ' %s' % tree_TYPE_NAME.DECL_NAME().IDENTIFIER_POINTER()
238 if self.node.TREE_CODE() == IDENTIFIER_NODE:
239 result += ' %s' % self.node.IDENTIFIER_POINTER()
244 ######################################################################
245 # Callgraph pretty-printers
246 ######################################################################
248 class CGraphNodePrinter:
249 def __init__(self, gdbval):
252 def to_string (self):
253 result = '<cgraph_node* 0x%x' % intptr(self.gdbval)
254 if intptr(self.gdbval):
255 # symtab_node::name calls lang_hooks.decl_printable_name
256 # default implementation (lhd_decl_printable_name) is:
257 # return IDENTIFIER_POINTER (DECL_NAME (decl));
258 tree_decl = Tree(self.gdbval['decl'])
259 result += ' "%s"' % tree_decl.DECL_NAME().IDENTIFIER_POINTER()
263 ######################################################################
264 # Dwarf DIE pretty-printers
265 ######################################################################
267 class DWDieRefPrinter:
268 def __init__(self, gdbval):
271 def to_string (self):
272 if intptr(self.gdbval) == 0:
273 return '<dw_die_ref 0x0>'
274 result = '<dw_die_ref 0x%x' % intptr(self.gdbval)
275 result += ' %s' % self.gdbval['die_tag']
276 if intptr(self.gdbval['die_parent']) != 0:
277 result += ' <parent=0x%x %s>' % (intptr(self.gdbval['die_parent']),
278 self.gdbval['die_parent']['die_tag'])
283 ######################################################################
286 def __init__(self, gdbval):
289 def to_string (self):
290 if intptr(self.gdbval) == 0:
291 return '<gimple 0x0>'
292 val_gimple_code = self.gdbval['code']
293 val_gimple_code_name = gdb.parse_and_eval('gimple_code_name')
294 val_code_name = val_gimple_code_name[intptr(val_gimple_code)]
295 result = '<%s 0x%x' % (val_code_name.string(),
300 ######################################################################
301 # CFG pretty-printers
302 ######################################################################
304 def bb_index_to_str(index):
312 class BasicBlockPrinter:
313 def __init__(self, gdbval):
316 def to_string (self):
317 result = '<basic_block 0x%x' % intptr(self.gdbval)
318 if intptr(self.gdbval):
319 result += ' (%s)' % bb_index_to_str(intptr(self.gdbval['index']))
323 class CfgEdgePrinter:
324 def __init__(self, gdbval):
327 def to_string (self):
328 result = '<edge 0x%x' % intptr(self.gdbval)
329 if intptr(self.gdbval):
330 src = bb_index_to_str(intptr(self.gdbval['src']['index']))
331 dest = bb_index_to_str(intptr(self.gdbval['dest']['index']))
332 result += ' (%s -> %s)' % (src, dest)
336 ######################################################################
339 def __init__(self, gdbval):
343 return self.gdbval['code']
345 def GET_RTX_LENGTH(code):
346 val_rtx_length = gdb.parse_and_eval('rtx_length')
347 return intptr(val_rtx_length[code])
349 def GET_RTX_NAME(code):
350 val_rtx_name = gdb.parse_and_eval('rtx_name')
351 return val_rtx_name[code].string()
353 def GET_RTX_FORMAT(code):
354 val_rtx_format = gdb.parse_and_eval('rtx_format')
355 return val_rtx_format[code].string()
358 def __init__(self, gdbval):
360 self.rtx = Rtx(gdbval)
362 def to_string (self):
364 For now, a cheap kludge: invoke the inferior's print
365 function to get a string to use the user, and return an empty
368 # We use print_inline_rtx to avoid a trailing newline
369 gdb.execute('call print_inline_rtx (stderr, (const_rtx) %s, 0)'
370 % intptr(self.gdbval))
373 # or by hand; based on gcc/print-rtl.c:print_rtx
374 result = ('<rtx_def 0x%x'
375 % (intptr(self.gdbval)))
376 code = self.rtx.GET_CODE()
377 result += ' (%s' % GET_RTX_NAME(code)
378 format_ = GET_RTX_FORMAT(code)
379 for i in range(GET_RTX_LENGTH(code)):
384 ######################################################################
387 def __init__(self, gdbval):
390 def to_string (self):
391 result = '<opt_pass* 0x%x' % intptr(self.gdbval)
392 if intptr(self.gdbval):
393 result += (' "%s"(%i)'
394 % (self.gdbval['name'].string(),
395 intptr(self.gdbval['static_pass_number'])))
399 ######################################################################
402 # -ex "up" -ex "p bb->preds"
403 def __init__(self, gdbval):
406 def display_hint (self):
409 def to_string (self):
410 # A trivial implementation; prettyprinting the contents is done
411 # by gdb calling the "children" method below.
412 return '0x%x' % intptr(self.gdbval)
415 if intptr(self.gdbval) == 0:
417 m_vecpfx = self.gdbval['m_vecpfx']
418 m_num = m_vecpfx['m_num']
419 m_vecdata = self.gdbval['m_vecdata']
420 for i in range(m_num):
421 yield ('[%d]' % i, m_vecdata[i])
423 ######################################################################
425 class MachineModePrinter:
426 def __init__(self, gdbval):
429 def to_string (self):
430 name = str(self.gdbval['m_mode'])
431 return name[2:] if name.startswith('E_') else name
433 ######################################################################
435 class OptMachineModePrinter:
436 def __init__(self, gdbval):
439 def to_string (self):
440 name = str(self.gdbval['m_mode'])
441 if name == 'E_VOIDmode':
443 return name[2:] if name.startswith('E_') else name
445 ######################################################################
451 class GdbSubprinter(gdb.printing.SubPrettyPrinter):
452 def __init__(self, name, class_):
453 super(GdbSubprinter, self).__init__(name)
456 def handles_type(self, str_type):
457 raise NotImplementedError
459 class GdbSubprinterTypeList(GdbSubprinter):
461 A GdbSubprinter that handles a specific set of types
463 def __init__(self, str_types, name, class_):
464 super(GdbSubprinterTypeList, self).__init__(name, class_)
465 self.str_types = frozenset(str_types)
467 def handles_type(self, str_type):
468 return str_type in self.str_types
470 class GdbSubprinterRegex(GdbSubprinter):
472 A GdbSubprinter that handles types that match a regex
474 def __init__(self, regex, name, class_):
475 super(GdbSubprinterRegex, self).__init__(name, class_)
476 self.regex = re.compile(regex)
478 def handles_type(self, str_type):
479 return self.regex.match(str_type)
481 class GdbPrettyPrinters(gdb.printing.PrettyPrinter):
482 def __init__(self, name):
483 super(GdbPrettyPrinters, self).__init__(name, [])
485 def add_printer_for_types(self, name, class_, types):
486 self.subprinters.append(GdbSubprinterTypeList(name, class_, types))
488 def add_printer_for_regex(self, name, class_, regex):
489 self.subprinters.append(GdbSubprinterRegex(name, class_, regex))
491 def __call__(self, gdbval):
492 type_ = gdbval.type.unqualified()
493 str_type = str(type_)
494 for printer in self.subprinters:
495 if printer.enabled and printer.handles_type(str_type):
496 return printer.class_(gdbval)
498 # Couldn't find a pretty printer (or it was disabled):
502 def build_pretty_printer():
503 pp = GdbPrettyPrinters('gcc')
504 pp.add_printer_for_types(['tree'],
506 pp.add_printer_for_types(['cgraph_node *'],
507 'cgraph_node', CGraphNodePrinter)
508 pp.add_printer_for_types(['dw_die_ref'],
509 'dw_die_ref', DWDieRefPrinter)
510 pp.add_printer_for_types(['gimple', 'gimple *',
512 # Keep this in the same order as gimple.def:
513 'gimple_cond', 'const_gimple_cond',
514 'gimple_statement_cond *',
515 'gimple_debug', 'const_gimple_debug',
516 'gimple_statement_debug *',
517 'gimple_label', 'const_gimple_label',
518 'gimple_statement_label *',
519 'gimple_switch', 'const_gimple_switch',
520 'gimple_statement_switch *',
521 'gimple_assign', 'const_gimple_assign',
522 'gimple_statement_assign *',
523 'gimple_bind', 'const_gimple_bind',
524 'gimple_statement_bind *',
525 'gimple_phi', 'const_gimple_phi',
526 'gimple_statement_phi *'],
530 pp.add_printer_for_types(['basic_block', 'basic_block_def *'],
533 pp.add_printer_for_types(['edge', 'edge_def *'],
536 pp.add_printer_for_types(['rtx_def *'], 'rtx_def', RtxPrinter)
537 pp.add_printer_for_types(['opt_pass *'], 'opt_pass', PassPrinter)
539 pp.add_printer_for_regex(r'vec<(\S+), (\S+), (\S+)> \*',
543 pp.add_printer_for_regex(r'opt_mode<(\S+)>',
544 'opt_mode', OptMachineModePrinter)
545 pp.add_printer_for_types(['opt_scalar_int_mode',
546 'opt_scalar_float_mode',
548 'opt_mode', OptMachineModePrinter)
549 pp.add_printer_for_regex(r'pod_mode<(\S+)>',
550 'pod_mode', MachineModePrinter)
551 pp.add_printer_for_types(['scalar_int_mode_pod',
553 'pod_mode', MachineModePrinter)
554 for mode in ('scalar_mode', 'scalar_int_mode', 'scalar_float_mode',
556 pp.add_printer_for_types([mode], mode, MachineModePrinter)
560 gdb.printing.register_pretty_printer(
561 gdb.current_objfile(),
562 build_pretty_printer())
564 def find_gcc_source_dir():
565 # Use location of global "g" to locate the source tree
566 sym_g = gdb.lookup_global_symbol('g')
567 path = sym_g.symtab.filename # e.g. '../../src/gcc/context.h'
568 srcdir = os.path.split(path)[0] # e.g. '../../src/gcc'
572 """Parse passes.def, gathering a list of pass class names"""
574 srcdir = find_gcc_source_dir()
576 with open(os.path.join(srcdir, 'passes.def')) as f:
578 m = re.match('\s*NEXT_PASS \(([^,]+).*\);', line)
580 self.names.append(m.group(1))
582 class BreakOnPass(gdb.Command):
584 A custom command for putting breakpoints on the execute hook of passes.
585 This is largely a workaround for issues with tab-completion in gdb when
586 setting breakpoints on methods on classes within anonymous namespaces.
588 Example of use: putting a breakpoint on "final"
590 Press <TAB>; it autocompletes to "pass_":
591 (gdb) break-on-pass pass_
593 Display all 219 possibilities? (y or n)
594 Press "n"; then type "f":
595 (gdb) break-on-pass pass_f
596 Press <TAB> to autocomplete to pass classnames beginning with "pass_f":
597 pass_fast_rtl_dce pass_fold_builtins
598 pass_feedback_split_functions pass_forwprop
600 pass_fixup_cfg pass_free_cfg
601 Type "in<TAB>" to complete to "pass_final":
602 (gdb) break-on-pass pass_final
604 Breakpoint 6 at 0x8396ba: file ../../src/gcc/final.c, line 4526.
605 ...and we have a breakpoint set; continue execution:
608 Breakpoint 6, (anonymous namespace)::pass_final::execute (this=0x17fb990) at ../../src/gcc/final.c:4526
609 4526 virtual unsigned int execute (function *) { return rest_of_handle_final (); }
612 gdb.Command.__init__(self, 'break-on-pass', gdb.COMMAND_BREAKPOINTS)
613 self.pass_names = None
615 def complete(self, text, word):
616 # Lazily load pass names:
617 if not self.pass_names:
618 self.pass_names = PassNames()
621 for name in sorted(self.pass_names.names)
622 if name.startswith(text)]
624 def invoke(self, arg, from_tty):
625 sym = '(anonymous namespace)::%s::execute' % arg
626 breakpoint = gdb.Breakpoint(sym)
630 class DumpFn(gdb.Command):
632 A custom command to dump a gimple/rtl function to file. By default, it
633 dumps the current function using 0 as dump_flags, but the function and flags
634 can also be specified. If /f <file> are passed as the first two arguments,
635 the dump is written to that file. Otherwise, a temporary file is created
636 and opened in the text editor specified in the EDITOR environment variable.
640 (gdb) dump-fn /f foo.1.txt
641 (gdb) dump-fn cfun->decl
642 (gdb) dump-fn /f foo.1.txt cfun->decl
643 (gdb) dump-fn cfun->decl 0
644 (gdb) dump-fn cfun->decl dump_flags
648 gdb.Command.__init__(self, 'dump-fn', gdb.COMMAND_USER)
650 def invoke(self, arg, from_tty):
651 # Parse args, check number of args
652 args = gdb.string_to_argv(arg)
653 if len(args) >= 1 and args[0] == "/f":
655 print ("Missing file argument")
661 editor = os.getenv("EDITOR", "")
663 print ("EDITOR environment variable not defined")
667 if len(args) - base_arg > 2:
668 print ("Too many arguments")
672 if len(args) - base_arg >= 1:
673 funcname = args[base_arg]
674 printfuncname = "function %s" % funcname
676 funcname = "cfun ? cfun->decl : current_function_decl"
677 printfuncname = "current function"
678 func = gdb.parse_and_eval(funcname)
680 print ("Could not find %s" % printfuncname)
682 func = "(tree)%u" % func
685 if len(args) - base_arg >= 2:
686 flags = gdb.parse_and_eval(args[base_arg + 1])
690 # Get tempory file, if necessary
692 f = tempfile.NamedTemporaryFile(delete=False, suffix=".txt")
697 fp = gdb.parse_and_eval("fopen (\"%s\", \"w\")" % filename)
699 print ("Could not open file: %s" % filename)
701 fp = "(FILE *)%u" % fp
703 # Dump function to file
704 _ = gdb.parse_and_eval("dump_function_to_file (%s, %s, %u)" %
708 ret = gdb.parse_and_eval("fclose (%s)" % fp)
710 print ("Could not close file: %s" % filename)
713 # Open file in editor, if necessary
715 os.system("( %s \"%s\"; rm \"%s\" ) &" %
716 (editor, filename, filename))
720 class DotFn(gdb.Command):
722 A custom command to show a gimple/rtl function control flow graph.
723 By default, it show the current function, but the function can also be
730 (gdb) dot-fn cfun dump_flags
733 gdb.Command.__init__(self, 'dot-fn', gdb.COMMAND_USER)
735 def invoke(self, arg, from_tty):
736 # Parse args, check number of args
737 args = gdb.string_to_argv(arg)
739 print("Too many arguments")
745 printfuncname = "function %s" % funcname
748 printfuncname = "current function"
749 func = gdb.parse_and_eval(funcname)
751 print("Could not find %s" % printfuncname)
753 func = "(struct function *)%s" % func
757 flags = gdb.parse_and_eval(args[1])
762 f = tempfile.NamedTemporaryFile(delete=False)
765 # Close and reopen temp file to get C FILE*
767 fp = gdb.parse_and_eval("fopen (\"%s\", \"w\")" % filename)
769 print("Cannot open temp file")
771 fp = "(FILE *)%u" % fp
773 # Write graph to temp file
774 _ = gdb.parse_and_eval("start_graph_dump (%s, \"<debug>\")" % fp)
775 _ = gdb.parse_and_eval("print_graph_cfg (%s, %s, %u)"
777 _ = gdb.parse_and_eval("end_graph_dump (%s)" % fp)
780 ret = gdb.parse_and_eval("fclose (%s)" % fp)
782 print("Could not close temp file: %s" % filename)
785 # Show graph in temp file
786 os.system("( dot -Tx11 \"%s\"; rm \"%s\" ) &" % (filename, filename))
790 print('Successfully loaded GDB hooks for GCC')