1# Python hooks for gdb for debugging GCC
2# Copyright (C) 2013-2014 Free Software Foundation, Inc.
3
4# Contributed by David Malcolm <dmalcolm@redhat.com>
5
6# This file is part of GCC.
7
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
11# version.
12
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
16# for more details.
17
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/>.
21
22"""
23Enabling the debugging hooks
24----------------------------
25gcc/configure (from configure.ac) generates a .gdbinit within the "gcc"
26subdirectory of the build directory, and when run by gdb, this imports
27gcc/gdbhooks.py from the source directory, injecting useful Python code
28into gdb.
29
30You 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'
32as a protection against untrustworthy python scripts.  See
33  http://sourceware.org/gdb/onlinedocs/gdb/Auto_002dloading-safe-path.html
34
35The fix is to mark the paths of the build/gcc directory as trustworthy.
36An 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
38for the build directories for your various checkouts of gcc.
39
40If it's working, you should see the message:
41  Successfully loaded GDB hooks for GCC
42as gdb starts up.
43
44During development, I've been manually invoking the code in this way, as a
45precanned way of printing a variety of different kinds of value:
46
47  gdb \
48    -ex "break expand_gimple_stmt" \
49    -ex "run" \
50    -ex "bt" \
51    --args \
52      ./cc1 foo.c -O3
53
54Examples of output using the pretty-printers
55--------------------------------------------
56Pointer values are generally shown in the form:
57  <type address extra_info>
58
59For example, an opt_pass* might appear as:
60  (gdb) p pass
61  $2 = <opt_pass* 0x188b600 "expand"(170)>
62
63The name of the pass is given ("expand"), together with the
64static_pass_number.
65
66Note that you can dereference the pointer in the normal way:
67  (gdb) p *pass
68  $4 = {type = RTL_PASS, name = 0x120a312 "expand",
69  [etc, ...snipped...]
70
71and you can suppress pretty-printers using /r (for "raw"):
72  (gdb) p /r pass
73  $3 = (opt_pass *) 0x188b600
74
75Basic blocks are shown with their index in parentheses, apart from the
76CFG's entry and exit blocks, which are given as "ENTRY" and "EXIT":
77  (gdb) p bb
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)>
83
84CFG edges are shown with the src and dest blocks given in parentheses:
85  (gdb) p e
86  $1 = <edge 0x7ffff043f118 (ENTRY -> 6)>
87
88Tree nodes are printed using Python code that emulates print_node_brief,
89running in gdb, rather than in the inferior:
90  (gdb) p cfun->decl
91  $1 = <function_decl 0x7ffff0420b00 foo>
92For usability, the type is printed first (e.g. "function_decl"), rather
93than just "tree".
94
95RTL expressions use a kludge: they are pretty-printed by injecting
96calls into print-rtl.c into the inferior:
97  Value returned is $1 = (note 9 8 10 [bb 3] NOTE_INSN_BASIC_BLOCK)
98  (gdb) p $1
99  $2 = (note 9 8 10 [bb 3] NOTE_INSN_BASIC_BLOCK)
100  (gdb) p /r $1
101  $3 = (rtx_def *) 0x7ffff043e140
102This won't work for coredumps, and probably in other circumstances, but
103it's a quick way of getting lots of debuggability quickly.
104
105Callgraph nodes are printed with the name of the function decl, if
106available:
107  (gdb) frame 5
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);
110  (gdb) p node
111  $1 = <cgraph_node* 0x7ffff0312720 "foo">
112
113vec<> pointers are printed as the address followed by the elements in
114braces.  Here's a length 2 vec:
115  (gdb) p bb->preds
116  $18 = 0x7ffff0428b68 = {<edge 0x7ffff044d380 (3 -> 5)>, <edge 0x7ffff044d3b8 (4 -> 5)>}
117
118and here's a length 1 vec:
119  (gdb) p bb->succs
120  $19 = 0x7ffff0428bb8 = {<edge 0x7ffff044d3f0 (5 -> EXIT)>}
121
122You cannot yet use array notation [] to access the elements within the
123vector: attempting to do so instead gives you the vec itself (for vec[0]),
124or a (probably) invalid cast to vec<> for the memory after the vec (for
125vec[1] onwards).
126
127Instead (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)>
132"""
133import re
134
135import gdb
136import gdb.printing
137import gdb.types
138
139# Convert "enum tree_code" (tree.def and tree.h) to a dict:
140tree_code_dict = gdb.types.make_enum_dict(gdb.lookup_type('enum tree_code'))
141
142# ...and look up specific values for use later:
143IDENTIFIER_NODE = tree_code_dict['IDENTIFIER_NODE']
144TYPE_DECL = tree_code_dict['TYPE_DECL']
145
146# Similarly for "enum tree_code_class" (tree.h):
147tree_code_class_dict = gdb.types.make_enum_dict(gdb.lookup_type('enum tree_code_class'))
148tcc_type = tree_code_class_dict['tcc_type']
149tcc_declaration = tree_code_class_dict['tcc_declaration']
150
151class Tree:
152    """
153    Wrapper around a gdb.Value for a tree, with various methods
154    corresponding to macros in gcc/tree.h
155    """
156    def __init__(self, gdbval):
157        self.gdbval = gdbval
158
159    def is_nonnull(self):
160        return long(self.gdbval)
161
162    def TREE_CODE(self):
163        """
164        Get gdb.Value corresponding to TREE_CODE (self)
165        as per:
166          #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
167        """
168        return self.gdbval['base']['code']
169
170    def DECL_NAME(self):
171        """
172        Get Tree instance corresponding to DECL_NAME (self)
173        """
174        return Tree(self.gdbval['decl_minimal']['name'])
175
176    def TYPE_NAME(self):
177        """
178        Get Tree instance corresponding to result of TYPE_NAME (self)
179        """
180        return Tree(self.gdbval['type_common']['name'])
181
182    def IDENTIFIER_POINTER(self):
183        """
184        Get str correspoinding to result of IDENTIFIER_NODE (self)
185        """
186        return self.gdbval['identifier']['id']['str'].string()
187
188class TreePrinter:
189    "Prints a tree"
190
191    def __init__ (self, gdbval):
192        self.gdbval = gdbval
193        self.node = Tree(gdbval)
194
195    def to_string (self):
196        # like gcc/print-tree.c:print_node_brief
197        # #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
198        # tree_code_name[(int) TREE_CODE (node)])
199        if long(self.gdbval) == 0:
200            return '<tree 0x0>'
201
202        val_TREE_CODE = self.node.TREE_CODE()
203
204        # extern const enum tree_code_class tree_code_type[];
205        # #define TREE_CODE_CLASS(CODE)	tree_code_type[(int) (CODE)]
206
207        val_tree_code_type = gdb.parse_and_eval('tree_code_type')
208        val_tclass = val_tree_code_type[val_TREE_CODE]
209
210        val_tree_code_name = gdb.parse_and_eval('tree_code_name')
211        val_code_name = val_tree_code_name[long(val_TREE_CODE)]
212        #print val_code_name.string()
213
214        result = '<%s 0x%x' % (val_code_name.string(), long(self.gdbval))
215        if long(val_tclass) == tcc_declaration:
216            tree_DECL_NAME = self.node.DECL_NAME()
217            if tree_DECL_NAME.is_nonnull():
218                 result += ' %s' % tree_DECL_NAME.IDENTIFIER_POINTER()
219            else:
220                pass # TODO: labels etc
221        elif long(val_tclass) == tcc_type:
222            tree_TYPE_NAME = Tree(self.gdbval['type_common']['name'])
223            if tree_TYPE_NAME.is_nonnull():
224                if tree_TYPE_NAME.TREE_CODE() == IDENTIFIER_NODE:
225                    result += ' %s' % tree_TYPE_NAME.IDENTIFIER_POINTER()
226                elif tree_TYPE_NAME.TREE_CODE() == TYPE_DECL:
227                    if tree_TYPE_NAME.DECL_NAME().is_nonnull():
228                        result += ' %s' % tree_TYPE_NAME.DECL_NAME().IDENTIFIER_POINTER()
229        if self.node.TREE_CODE() == IDENTIFIER_NODE:
230            result += ' %s' % self.node.IDENTIFIER_POINTER()
231        # etc
232        result += '>'
233        return result
234
235######################################################################
236# Callgraph pretty-printers
237######################################################################
238
239class CGraphNodePrinter:
240    def __init__(self, gdbval):
241        self.gdbval = gdbval
242
243    def to_string (self):
244        result = '<cgraph_node* 0x%x' % long(self.gdbval)
245        if long(self.gdbval):
246            # symtab_node::name calls lang_hooks.decl_printable_name
247            # default implementation (lhd_decl_printable_name) is:
248            #    return IDENTIFIER_POINTER (DECL_NAME (decl));
249            tree_decl = Tree(self.gdbval['decl'])
250            result += ' "%s"' % tree_decl.DECL_NAME().IDENTIFIER_POINTER()
251        result += '>'
252        return result
253
254######################################################################
255
256class GimplePrinter:
257    def __init__(self, gdbval):
258        self.gdbval = gdbval
259
260    def to_string (self):
261        if long(self.gdbval) == 0:
262            return '<gimple 0x0>'
263        val_gimple_code = self.gdbval['code']
264        val_gimple_code_name = gdb.parse_and_eval('gimple_code_name')
265        val_code_name = val_gimple_code_name[long(val_gimple_code)]
266        result = '<%s 0x%x' % (val_code_name.string(),
267                               long(self.gdbval))
268        result += '>'
269        return result
270
271######################################################################
272# CFG pretty-printers
273######################################################################
274
275def bb_index_to_str(index):
276    if index == 0:
277        return 'ENTRY'
278    elif index == 1:
279        return 'EXIT'
280    else:
281        return '%i' % index
282
283class BasicBlockPrinter:
284    def __init__(self, gdbval):
285        self.gdbval = gdbval
286
287    def to_string (self):
288        result = '<basic_block 0x%x' % long(self.gdbval)
289        if long(self.gdbval):
290            result += ' (%s)' % bb_index_to_str(long(self.gdbval['index']))
291        result += '>'
292        return result
293
294class CfgEdgePrinter:
295    def __init__(self, gdbval):
296        self.gdbval = gdbval
297
298    def to_string (self):
299        result = '<edge 0x%x' % long(self.gdbval)
300        if long(self.gdbval):
301            src = bb_index_to_str(long(self.gdbval['src']['index']))
302            dest = bb_index_to_str(long(self.gdbval['dest']['index']))
303            result += ' (%s -> %s)' % (src, dest)
304        result += '>'
305        return result
306
307######################################################################
308
309class Rtx:
310    def __init__(self, gdbval):
311        self.gdbval = gdbval
312
313    def GET_CODE(self):
314        return self.gdbval['code']
315
316def GET_RTX_LENGTH(code):
317    val_rtx_length = gdb.parse_and_eval('rtx_length')
318    return long(val_rtx_length[code])
319
320def GET_RTX_NAME(code):
321    val_rtx_name = gdb.parse_and_eval('rtx_name')
322    return val_rtx_name[code].string()
323
324def GET_RTX_FORMAT(code):
325    val_rtx_format = gdb.parse_and_eval('rtx_format')
326    return val_rtx_format[code].string()
327
328class RtxPrinter:
329    def __init__(self, gdbval):
330        self.gdbval = gdbval
331        self.rtx = Rtx(gdbval)
332
333    def to_string (self):
334        """
335        For now, a cheap kludge: invoke the inferior's print
336        function to get a string to use the user, and return an empty
337        string for gdb
338        """
339        # We use print_inline_rtx to avoid a trailing newline
340        gdb.execute('call print_inline_rtx (stderr, (const_rtx) %s, 0)'
341                    % long(self.gdbval))
342        return ''
343
344        # or by hand; based on gcc/print-rtl.c:print_rtx
345        result = ('<rtx_def 0x%x'
346                  % (long(self.gdbval)))
347        code = self.rtx.GET_CODE()
348        result += ' (%s' % GET_RTX_NAME(code)
349        format_ = GET_RTX_FORMAT(code)
350        for i in range(GET_RTX_LENGTH(code)):
351            print format_[i]
352        result += ')>'
353        return result
354
355######################################################################
356
357class PassPrinter:
358    def __init__(self, gdbval):
359        self.gdbval = gdbval
360
361    def to_string (self):
362        result = '<opt_pass* 0x%x' % long(self.gdbval)
363        if long(self.gdbval):
364            result += (' "%s"(%i)'
365                       % (self.gdbval['name'].string(),
366                          long(self.gdbval['static_pass_number'])))
367        result += '>'
368        return result
369
370######################################################################
371
372class VecPrinter:
373    #    -ex "up" -ex "p bb->preds"
374    def __init__(self, gdbval):
375        self.gdbval = gdbval
376
377    def display_hint (self):
378        return 'array'
379
380    def to_string (self):
381        # A trivial implementation; prettyprinting the contents is done
382        # by gdb calling the "children" method below.
383        return '0x%x' % long(self.gdbval)
384
385    def children (self):
386        if long(self.gdbval) == 0:
387            return
388        m_vecpfx = self.gdbval['m_vecpfx']
389        m_num = m_vecpfx['m_num']
390        m_vecdata = self.gdbval['m_vecdata']
391        for i in range(m_num):
392            yield ('[%d]' % i, m_vecdata[i])
393
394######################################################################
395
396# TODO:
397#   * hashtab
398#   * location_t
399
400class GdbSubprinter(gdb.printing.SubPrettyPrinter):
401    def __init__(self, name, class_):
402        super(GdbSubprinter, self).__init__(name)
403        self.class_ = class_
404
405    def handles_type(self, str_type):
406        raise NotImplementedError
407
408class GdbSubprinterTypeList(GdbSubprinter):
409    """
410    A GdbSubprinter that handles a specific set of types
411    """
412    def __init__(self, str_types, name, class_):
413        super(GdbSubprinterTypeList, self).__init__(name, class_)
414        self.str_types = frozenset(str_types)
415
416    def handles_type(self, str_type):
417        return str_type in self.str_types
418
419class GdbSubprinterRegex(GdbSubprinter):
420    """
421    A GdbSubprinter that handles types that match a regex
422    """
423    def __init__(self, regex, name, class_):
424        super(GdbSubprinterRegex, self).__init__(name, class_)
425        self.regex = re.compile(regex)
426
427    def handles_type(self, str_type):
428        return self.regex.match(str_type)
429
430class GdbPrettyPrinters(gdb.printing.PrettyPrinter):
431    def __init__(self, name):
432        super(GdbPrettyPrinters, self).__init__(name, [])
433
434    def add_printer_for_types(self, name, class_, types):
435        self.subprinters.append(GdbSubprinterTypeList(name, class_, types))
436
437    def add_printer_for_regex(self, name, class_, regex):
438        self.subprinters.append(GdbSubprinterRegex(name, class_, regex))
439
440    def __call__(self, gdbval):
441        type_ = gdbval.type.unqualified()
442        str_type = str(type_)
443        for printer in self.subprinters:
444            if printer.enabled and printer.handles_type(str_type):
445                return printer.class_(gdbval)
446
447        # Couldn't find a pretty printer (or it was disabled):
448        return None
449
450
451def build_pretty_printer():
452    pp = GdbPrettyPrinters('gcc')
453    pp.add_printer_for_types(['tree'],
454                             'tree', TreePrinter)
455    pp.add_printer_for_types(['cgraph_node *'],
456                             'cgraph_node', CGraphNodePrinter)
457    pp.add_printer_for_types(['gimple', 'gimple_statement_base *'],
458                             'gimple',
459                             GimplePrinter)
460    pp.add_printer_for_types(['basic_block', 'basic_block_def *'],
461                             'basic_block',
462                             BasicBlockPrinter)
463    pp.add_printer_for_types(['edge', 'edge_def *'],
464                             'edge',
465                             CfgEdgePrinter)
466    pp.add_printer_for_types(['rtx_def *'], 'rtx_def', RtxPrinter)
467    pp.add_printer_for_types(['opt_pass *'], 'opt_pass', PassPrinter)
468
469    pp.add_printer_for_regex(r'vec<(\S+), (\S+), (\S+)> \*',
470                             'vec',
471                             VecPrinter)
472
473    return pp
474
475gdb.printing.register_pretty_printer(
476    gdb.current_objfile(),
477    build_pretty_printer())
478
479print('Successfully loaded GDB hooks for GCC')
480