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30ba058f | 1 | /* -Winfinite-recursion support. |
aeee4812 | 2 | Copyright (C) 2021-2023 Free Software Foundation, Inc. |
30ba058f MS |
3 | Contributed by Martin Sebor <msebor@redhat.com> |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 3, or (at your option) | |
10 | any later version. | |
11 | ||
12 | GCC is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with GCC; see the file COPYING3. If not see | |
19 | <http://www.gnu.org/licenses/>. */ | |
20 | ||
21 | #include "config.h" | |
22 | #include "system.h" | |
23 | #include "coretypes.h" | |
24 | #include "backend.h" | |
25 | #include "tree.h" | |
26 | #include "gimple.h" | |
27 | #include "tree-pass.h" | |
28 | #include "ssa.h" | |
29 | #include "diagnostic-core.h" | |
30 | // #include "tree-dfa.h" | |
31 | #include "attribs.h" | |
32 | #include "gimple-iterator.h" | |
33 | ||
34 | namespace { | |
35 | ||
36 | const pass_data warn_recursion_data = | |
37 | { | |
38 | GIMPLE_PASS, /* type */ | |
39 | "*infinite-recursion", /* name */ | |
40 | OPTGROUP_NONE, /* optinfo_flags */ | |
41 | TV_NONE, /* tv_id */ | |
42 | PROP_ssa, /* properties_required */ | |
43 | 0, /* properties_provided */ | |
44 | 0, /* properties_destroyed */ | |
45 | 0, /* todo_flags_start */ | |
46 | 0, /* todo_flags_finish */ | |
47 | }; | |
48 | ||
49 | class pass_warn_recursion : public gimple_opt_pass | |
50 | { | |
51 | public: | |
52 | pass_warn_recursion (gcc::context *); | |
53 | ||
54 | private: | |
725793af | 55 | bool gate (function *) final override { return warn_infinite_recursion; } |
30ba058f | 56 | |
725793af | 57 | unsigned int execute (function *) final override; |
30ba058f MS |
58 | |
59 | bool find_function_exit (basic_block); | |
60 | ||
61 | /* Recursive calls found in M_FUNC. */ | |
62 | vec<gimple *> *m_calls; | |
63 | /* Basic blocks already visited in the current function. */ | |
64 | bitmap m_visited; | |
65 | /* The current function. */ | |
66 | function *m_func; | |
67 | /* The current function code if it's (also) a built-in. */ | |
68 | built_in_function m_built_in; | |
69 | /* True if M_FUNC is a noreturn function. */ | |
70 | bool noreturn_p; | |
71 | }; | |
72 | ||
73 | /* Initialize the pass and its members. */ | |
74 | ||
75 | pass_warn_recursion::pass_warn_recursion (gcc::context *ctxt) | |
76 | : gimple_opt_pass (warn_recursion_data, ctxt), | |
77 | m_calls (), m_visited (), m_func (), m_built_in (), noreturn_p () | |
78 | { | |
79 | } | |
80 | ||
81 | /* Return true if there is path from BB to M_FUNC exit point along which | |
82 | there is no (recursive) call to M_FUNC. */ | |
83 | ||
84 | bool | |
85 | pass_warn_recursion::find_function_exit (basic_block bb) | |
86 | { | |
87 | if (!bitmap_set_bit (m_visited, bb->index)) | |
88 | return false; | |
89 | ||
90 | if (bb == EXIT_BLOCK_PTR_FOR_FN (m_func)) | |
91 | return true; | |
92 | ||
93 | /* Iterate over statements in BB, looking for a call to FNDECL. */ | |
94 | for (auto si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next_nondebug (&si)) | |
95 | { | |
96 | gimple *stmt = gsi_stmt (si); | |
97 | if (!is_gimple_call (stmt)) | |
98 | continue; | |
99 | ||
100 | if (gimple_call_builtin_p (stmt, BUILT_IN_LONGJMP)) | |
101 | /* A longjmp breaks infinite recursion. */ | |
102 | return true; | |
103 | ||
104 | if (tree fndecl = gimple_call_fndecl (stmt)) | |
105 | { | |
106 | /* A throw statement breaks infinite recursion. */ | |
107 | tree id = DECL_NAME (fndecl); | |
108 | const char *name = IDENTIFIER_POINTER (id); | |
109 | if (startswith (name, "__cxa_throw")) | |
110 | return true; | |
111 | /* As does a call to POSIX siglongjmp. */ | |
112 | if (!strcmp (name, "siglongjmp")) | |
113 | return true; | |
114 | ||
c8cb5098 JJ |
115 | if (m_built_in |
116 | && gimple_call_builtin_p (stmt, BUILT_IN_NORMAL) | |
30ba058f MS |
117 | && m_built_in == DECL_FUNCTION_CODE (fndecl)) |
118 | { | |
c8cb5098 JJ |
119 | const char *cname |
120 | = IDENTIFIER_POINTER (DECL_NAME (current_function_decl)); | |
121 | /* Don't warn about gnu_inline extern inline function | |
122 | like strcpy calling __builtin_strcpy, that is fine, | |
123 | if some call is made (the builtin isn't expanded inline), | |
124 | a call is made to the external definition. */ | |
125 | if (!(DECL_DECLARED_INLINE_P (current_function_decl) | |
126 | && DECL_EXTERNAL (current_function_decl)) | |
127 | || strcmp (name, cname) == 0) | |
128 | { | |
129 | /* The call is being made from the definition of a built-in | |
130 | (e.g., in a replacement of one) to itself. */ | |
131 | m_calls->safe_push (stmt); | |
132 | return false; | |
133 | } | |
30ba058f MS |
134 | } |
135 | } | |
136 | ||
137 | if (noreturn_p) | |
138 | { | |
139 | /* A noreturn call breaks infinite recursion. */ | |
140 | int flags = gimple_call_flags (stmt); | |
141 | if (flags & ECF_NORETURN) | |
142 | return true; | |
143 | } | |
144 | ||
145 | tree callee = gimple_call_fndecl (stmt); | |
146 | if (!callee || m_func->decl != callee) | |
147 | continue; | |
148 | ||
149 | /* Add the recursive call to the vector and return false. */ | |
150 | m_calls->safe_push (stmt); | |
151 | return false; | |
152 | } | |
153 | ||
154 | /* If no call to FNDECL has been found search all BB's successors. */ | |
155 | edge e; | |
156 | edge_iterator ei; | |
157 | FOR_EACH_EDGE (e, ei, bb->succs) | |
158 | if (find_function_exit (e->dest)) | |
159 | return true; | |
160 | ||
161 | return false; | |
162 | } | |
163 | ||
164 | ||
165 | /* Search FUNC for unconditionally infinitely recursive calls to self | |
166 | and issue a warning if it is such a function. */ | |
167 | ||
168 | unsigned int | |
169 | pass_warn_recursion::execute (function *func) | |
170 | { | |
171 | auto_bitmap visited; | |
172 | auto_vec<gimple *> calls; | |
173 | ||
174 | m_visited = visited; | |
175 | m_calls = &calls; | |
176 | m_func = func; | |
177 | ||
178 | /* Avoid diagnosing an apparently infinitely recursive function that | |
179 | doesn't return where the infinite recursion might be avoided by | |
180 | a call to another noreturn function. */ | |
181 | noreturn_p = lookup_attribute ("noreturn", DECL_ATTRIBUTES (m_func->decl)); | |
182 | ||
183 | if (fndecl_built_in_p (m_func->decl, BUILT_IN_NORMAL)) | |
184 | m_built_in = DECL_FUNCTION_CODE (m_func->decl); | |
185 | else | |
186 | m_built_in = BUILT_IN_NONE; | |
187 | ||
188 | basic_block entry_bb = ENTRY_BLOCK_PTR_FOR_FN (func); | |
189 | ||
190 | if (find_function_exit (entry_bb) || m_calls->length () == 0) | |
191 | return 0; | |
192 | ||
193 | if (warning_at (DECL_SOURCE_LOCATION (func->decl), | |
194 | OPT_Winfinite_recursion, | |
195 | "infinite recursion detected")) | |
196 | for (auto stmt: *m_calls) | |
197 | { | |
198 | location_t loc = gimple_location (stmt); | |
199 | if (loc == UNKNOWN_LOCATION) | |
200 | continue; | |
201 | ||
202 | inform (loc, "recursive call"); | |
203 | } | |
204 | ||
205 | return 0; | |
206 | } | |
207 | ||
208 | } // namespace | |
209 | ||
210 | gimple_opt_pass * | |
211 | make_pass_warn_recursion (gcc::context *ctxt) | |
212 | { | |
213 | return new pass_warn_recursion (ctxt); | |
214 | } |