1 # Python hooks for gdb for debugging GCC
2 # Copyright (C) 2013-2014 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)>
140 # Convert "enum tree_code" (tree.def and tree.h) to a dict:
141 tree_code_dict
= gdb
.types
.make_enum_dict(gdb
.lookup_type('enum tree_code'))
143 # ...and look up specific values for use later:
144 IDENTIFIER_NODE
= tree_code_dict
['IDENTIFIER_NODE']
145 TYPE_DECL
= tree_code_dict
['TYPE_DECL']
147 # Similarly for "enum tree_code_class" (tree.h):
148 tree_code_class_dict
= gdb
.types
.make_enum_dict(gdb
.lookup_type('enum tree_code_class'))
149 tcc_type
= tree_code_class_dict
['tcc_type']
150 tcc_declaration
= tree_code_class_dict
['tcc_declaration']
154 Wrapper around a gdb.Value for a tree, with various methods
155 corresponding to macros in gcc/tree.h
157 def __init__(self
, gdbval
):
160 def is_nonnull(self
):
161 return long(self
.gdbval
)
165 Get gdb.Value corresponding to TREE_CODE (self)
167 #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
169 return self
.gdbval
['base']['code']
173 Get Tree instance corresponding to DECL_NAME (self)
175 return Tree(self
.gdbval
['decl_minimal']['name'])
179 Get Tree instance corresponding to result of TYPE_NAME (self)
181 return Tree(self
.gdbval
['type_common']['name'])
183 def IDENTIFIER_POINTER(self
):
185 Get str correspoinding to result of IDENTIFIER_NODE (self)
187 return self
.gdbval
['identifier']['id']['str'].string()
192 def __init__ (self
, gdbval
):
194 self
.node
= Tree(gdbval
)
196 def to_string (self
):
197 # like gcc/print-tree.c:print_node_brief
198 # #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
199 # tree_code_name[(int) TREE_CODE (node)])
200 if long(self
.gdbval
) == 0:
203 val_TREE_CODE
= self
.node
.TREE_CODE()
205 # extern const enum tree_code_class tree_code_type[];
206 # #define TREE_CODE_CLASS(CODE) tree_code_type[(int) (CODE)]
208 val_tree_code_type
= gdb
.parse_and_eval('tree_code_type')
209 val_tclass
= val_tree_code_type
[val_TREE_CODE
]
211 val_tree_code_name
= gdb
.parse_and_eval('tree_code_name')
212 val_code_name
= val_tree_code_name
[long(val_TREE_CODE
)]
213 #print val_code_name.string()
215 result
= '<%s 0x%x' % (val_code_name
.string(), long(self
.gdbval
))
216 if long(val_tclass
) == tcc_declaration
:
217 tree_DECL_NAME
= self
.node
.DECL_NAME()
218 if tree_DECL_NAME
.is_nonnull():
219 result
+= ' %s' % tree_DECL_NAME
.IDENTIFIER_POINTER()
221 pass # TODO: labels etc
222 elif long(val_tclass
) == tcc_type
:
223 tree_TYPE_NAME
= Tree(self
.gdbval
['type_common']['name'])
224 if tree_TYPE_NAME
.is_nonnull():
225 if tree_TYPE_NAME
.TREE_CODE() == IDENTIFIER_NODE
:
226 result
+= ' %s' % tree_TYPE_NAME
.IDENTIFIER_POINTER()
227 elif tree_TYPE_NAME
.TREE_CODE() == TYPE_DECL
:
228 if tree_TYPE_NAME
.DECL_NAME().is_nonnull():
229 result
+= ' %s' % tree_TYPE_NAME
.DECL_NAME().IDENTIFIER_POINTER()
230 if self
.node
.TREE_CODE() == IDENTIFIER_NODE
:
231 result
+= ' %s' % self
.node
.IDENTIFIER_POINTER()
236 ######################################################################
237 # Callgraph pretty-printers
238 ######################################################################
240 class CGraphNodePrinter
:
241 def __init__(self
, gdbval
):
244 def to_string (self
):
245 result
= '<cgraph_node* 0x%x' % long(self
.gdbval
)
246 if long(self
.gdbval
):
247 # symtab_node::name calls lang_hooks.decl_printable_name
248 # default implementation (lhd_decl_printable_name) is:
249 # return IDENTIFIER_POINTER (DECL_NAME (decl));
250 tree_decl
= Tree(self
.gdbval
['decl'])
251 result
+= ' "%s"' % tree_decl
.DECL_NAME().IDENTIFIER_POINTER()
255 ######################################################################
258 def __init__(self
, gdbval
):
261 def to_string (self
):
262 if long(self
.gdbval
) == 0:
263 return '<gimple 0x0>'
264 val_gimple_code
= self
.gdbval
['code']
265 val_gimple_code_name
= gdb
.parse_and_eval('gimple_code_name')
266 val_code_name
= val_gimple_code_name
[long(val_gimple_code
)]
267 result
= '<%s 0x%x' % (val_code_name
.string(),
272 ######################################################################
273 # CFG pretty-printers
274 ######################################################################
276 def bb_index_to_str(index
):
284 class BasicBlockPrinter
:
285 def __init__(self
, gdbval
):
288 def to_string (self
):
289 result
= '<basic_block 0x%x' % long(self
.gdbval
)
290 if long(self
.gdbval
):
291 result
+= ' (%s)' % bb_index_to_str(long(self
.gdbval
['index']))
295 class CfgEdgePrinter
:
296 def __init__(self
, gdbval
):
299 def to_string (self
):
300 result
= '<edge 0x%x' % long(self
.gdbval
)
301 if long(self
.gdbval
):
302 src
= bb_index_to_str(long(self
.gdbval
['src']['index']))
303 dest
= bb_index_to_str(long(self
.gdbval
['dest']['index']))
304 result
+= ' (%s -> %s)' % (src
, dest
)
308 ######################################################################
311 def __init__(self
, gdbval
):
315 return self
.gdbval
['code']
317 def GET_RTX_LENGTH(code
):
318 val_rtx_length
= gdb
.parse_and_eval('rtx_length')
319 return long(val_rtx_length
[code
])
321 def GET_RTX_NAME(code
):
322 val_rtx_name
= gdb
.parse_and_eval('rtx_name')
323 return val_rtx_name
[code
].string()
325 def GET_RTX_FORMAT(code
):
326 val_rtx_format
= gdb
.parse_and_eval('rtx_format')
327 return val_rtx_format
[code
].string()
330 def __init__(self
, gdbval
):
332 self
.rtx
= Rtx(gdbval
)
334 def to_string (self
):
336 For now, a cheap kludge: invoke the inferior's print
337 function to get a string to use the user, and return an empty
340 # We use print_inline_rtx to avoid a trailing newline
341 gdb
.execute('call print_inline_rtx (stderr, (const_rtx) %s, 0)'
345 # or by hand; based on gcc/print-rtl.c:print_rtx
346 result
= ('<rtx_def 0x%x'
347 % (long(self
.gdbval
)))
348 code
= self
.rtx
.GET_CODE()
349 result
+= ' (%s' % GET_RTX_NAME(code
)
350 format_
= GET_RTX_FORMAT(code
)
351 for i
in range(GET_RTX_LENGTH(code
)):
356 ######################################################################
359 def __init__(self
, gdbval
):
362 def to_string (self
):
363 result
= '<opt_pass* 0x%x' % long(self
.gdbval
)
364 if long(self
.gdbval
):
365 result
+= (' "%s"(%i)'
366 % (self
.gdbval
['name'].string(),
367 long(self
.gdbval
['static_pass_number'])))
371 ######################################################################
374 # -ex "up" -ex "p bb->preds"
375 def __init__(self
, gdbval
):
378 def display_hint (self
):
381 def to_string (self
):
382 # A trivial implementation; prettyprinting the contents is done
383 # by gdb calling the "children" method below.
384 return '0x%x' % long(self
.gdbval
)
387 if long(self
.gdbval
) == 0:
389 m_vecpfx
= self
.gdbval
['m_vecpfx']
390 m_num
= m_vecpfx
['m_num']
391 m_vecdata
= self
.gdbval
['m_vecdata']
392 for i
in range(m_num
):
393 yield ('[%d]' % i
, m_vecdata
[i
])
395 ######################################################################
401 class GdbSubprinter(gdb
.printing
.SubPrettyPrinter
):
402 def __init__(self
, name
, class_
):
403 super(GdbSubprinter
, self
).__init
__(name
)
406 def handles_type(self
, str_type
):
407 raise NotImplementedError
409 class GdbSubprinterTypeList(GdbSubprinter
):
411 A GdbSubprinter that handles a specific set of types
413 def __init__(self
, str_types
, name
, class_
):
414 super(GdbSubprinterTypeList
, self
).__init
__(name
, class_
)
415 self
.str_types
= frozenset(str_types
)
417 def handles_type(self
, str_type
):
418 return str_type
in self
.str_types
420 class GdbSubprinterRegex(GdbSubprinter
):
422 A GdbSubprinter that handles types that match a regex
424 def __init__(self
, regex
, name
, class_
):
425 super(GdbSubprinterRegex
, self
).__init
__(name
, class_
)
426 self
.regex
= re
.compile(regex
)
428 def handles_type(self
, str_type
):
429 return self
.regex
.match(str_type
)
431 class GdbPrettyPrinters(gdb
.printing
.PrettyPrinter
):
432 def __init__(self
, name
):
433 super(GdbPrettyPrinters
, self
).__init
__(name
, [])
435 def add_printer_for_types(self
, name
, class_
, types
):
436 self
.subprinters
.append(GdbSubprinterTypeList(name
, class_
, types
))
438 def add_printer_for_regex(self
, name
, class_
, regex
):
439 self
.subprinters
.append(GdbSubprinterRegex(name
, class_
, regex
))
441 def __call__(self
, gdbval
):
442 type_
= gdbval
.type.unqualified()
443 str_type
= str(type_
)
444 for printer
in self
.subprinters
:
445 if printer
.enabled
and printer
.handles_type(str_type
):
446 return printer
.class_(gdbval
)
448 # Couldn't find a pretty printer (or it was disabled):
452 def build_pretty_printer():
453 pp
= GdbPrettyPrinters('gcc')
454 pp
.add_printer_for_types(['tree'],
456 pp
.add_printer_for_types(['cgraph_node *'],
457 'cgraph_node', CGraphNodePrinter
)
458 pp
.add_printer_for_types(['gimple', 'gimple_statement_base *',
460 # Keep this in the same order as gimple.def:
461 'gimple_cond', 'const_gimple_cond',
462 'gimple_statement_cond *',
463 'gimple_debug', 'const_gimple_debug',
464 'gimple_statement_debug *',
465 'gimple_label', 'const_gimple_label',
466 'gimple_statement_label *',
467 'gimple_switch', 'const_gimple_switch',
468 'gimple_statement_switch *',
469 'gimple_assign', 'const_gimple_assign',
470 'gimple_statement_assign *',
471 'gimple_bind', 'const_gimple_bind',
472 'gimple_statement_bind *'],
476 pp
.add_printer_for_types(['basic_block', 'basic_block_def *'],
479 pp
.add_printer_for_types(['edge', 'edge_def *'],
482 pp
.add_printer_for_types(['rtx_def *'], 'rtx_def', RtxPrinter
)
483 pp
.add_printer_for_types(['opt_pass *'], 'opt_pass', PassPrinter
)
485 pp
.add_printer_for_regex(r
'vec<(\S+), (\S+), (\S+)> \*',
491 gdb
.printing
.register_pretty_printer(
492 gdb
.current_objfile(),
493 build_pretty_printer())
495 def find_gcc_source_dir():
496 # Use location of global "g" to locate the source tree
497 sym_g
= gdb
.lookup_global_symbol('g')
498 path
= sym_g
.symtab
.filename
# e.g. '../../src/gcc/context.h'
499 srcdir
= os
.path
.split(path
)[0] # e.g. '../../src/gcc'
503 """Parse passes.def, gathering a list of pass class names"""
505 srcdir
= find_gcc_source_dir()
507 with
open(os
.path
.join(srcdir
, 'passes.def')) as f
:
509 m
= re
.match('\s*NEXT_PASS \((.+)\);', line
)
511 self
.names
.append(m
.group(1))
513 class BreakOnPass(gdb
.Command
):
515 A custom command for putting breakpoints on the execute hook of passes.
516 This is largely a workaround for issues with tab-completion in gdb when
517 setting breakpoints on methods on classes within anonymous namespaces.
519 Example of use: putting a breakpoint on "final"
521 Press <TAB>; it autocompletes to "pass_":
522 (gdb) break-on-pass pass_
524 Display all 219 possibilities? (y or n)
525 Press "n"; then type "f":
526 (gdb) break-on-pass pass_f
527 Press <TAB> to autocomplete to pass classnames beginning with "pass_f":
528 pass_fast_rtl_dce pass_fold_builtins
529 pass_feedback_split_functions pass_forwprop
531 pass_fixup_cfg pass_free_cfg
532 Type "in<TAB>" to complete to "pass_final":
533 (gdb) break-on-pass pass_final
535 Breakpoint 6 at 0x8396ba: file ../../src/gcc/final.c, line 4526.
536 ...and we have a breakpoint set; continue execution:
539 Breakpoint 6, (anonymous namespace)::pass_final::execute (this=0x17fb990) at ../../src/gcc/final.c:4526
540 4526 virtual unsigned int execute (function *) { return rest_of_handle_final (); }
543 gdb
.Command
.__init
__(self
, 'break-on-pass', gdb
.COMMAND_BREAKPOINTS
)
544 self
.pass_names
= None
546 def complete(self
, text
, word
):
547 # Lazily load pass names:
548 if not self
.pass_names
:
549 self
.pass_names
= PassNames()
552 for name
in sorted(self
.pass_names
.names
)
553 if name
.startswith(text
)]
555 def invoke(self
, arg
, from_tty
):
556 sym
= '(anonymous namespace)::%s::execute' % arg
557 breakpoint
= gdb
.Breakpoint(sym
)
561 print('Successfully loaded GDB hooks for GCC')