1 | /* -Winfinite-recursion support. |
2 | Copyright (C) 2021-2023 Free Software Foundation, Inc. |
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 | .type: GIMPLE_PASS, /* type */ |
39 | .name: "*infinite-recursion" , /* name */ |
40 | .optinfo_flags: OPTGROUP_NONE, /* optinfo_flags */ |
41 | .tv_id: TV_NONE, /* tv_id */ |
42 | PROP_ssa, /* properties_required */ |
43 | .properties_provided: 0, /* properties_provided */ |
44 | .properties_destroyed: 0, /* properties_destroyed */ |
45 | .todo_flags_start: 0, /* todo_flags_start */ |
46 | .todo_flags_finish: 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: |
55 | bool gate (function *) final override { return warn_infinite_recursion; } |
56 | |
57 | unsigned int execute (function *) final override; |
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 (i: si); gsi_next_nondebug (i: &si)) |
95 | { |
96 | gimple *stmt = gsi_stmt (i: si); |
97 | if (!is_gimple_call (gs: 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 (gs: 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 (str: name, prefix: "__cxa_throw" )) |
110 | return true; |
111 | /* As does a call to POSIX siglongjmp. */ |
112 | if (!strcmp (s1: name, s2: "siglongjmp" )) |
113 | return true; |
114 | |
115 | if (m_built_in |
116 | && gimple_call_builtin_p (stmt, BUILT_IN_NORMAL) |
117 | && m_built_in == DECL_FUNCTION_CODE (decl: fndecl)) |
118 | { |
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 (s1: name, s2: 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 (obj: stmt); |
132 | return false; |
133 | } |
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 (gs: 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 (obj: 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 (bb: 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 (attr_name: "noreturn" , DECL_ATTRIBUTES (m_func->decl)); |
182 | |
183 | if (fndecl_built_in_p (node: m_func->decl, klass: BUILT_IN_NORMAL)) |
184 | m_built_in = DECL_FUNCTION_CODE (decl: 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 (bb: 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 (g: 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 | } |
215 | |