| /* -Winfinite-recursion support. |
| Copyright (C) 2021-2022 Free Software Foundation, Inc. |
| Contributed by Martin Sebor <msebor@redhat.com> |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| GCC is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GCC; see the file COPYING3. If not see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "tree-pass.h" |
| #include "ssa.h" |
| #include "diagnostic-core.h" |
| // #include "tree-dfa.h" |
| #include "attribs.h" |
| #include "gimple-iterator.h" |
| |
| namespace { |
| |
| const pass_data warn_recursion_data = |
| { |
| GIMPLE_PASS, /* type */ |
| "*infinite-recursion", /* name */ |
| OPTGROUP_NONE, /* optinfo_flags */ |
| TV_NONE, /* tv_id */ |
| PROP_ssa, /* properties_required */ |
| 0, /* properties_provided */ |
| 0, /* properties_destroyed */ |
| 0, /* todo_flags_start */ |
| 0, /* todo_flags_finish */ |
| }; |
| |
| class pass_warn_recursion : public gimple_opt_pass |
| { |
| public: |
| pass_warn_recursion (gcc::context *); |
| |
| private: |
| bool gate (function *) final override { return warn_infinite_recursion; } |
| |
| unsigned int execute (function *) final override; |
| |
| bool find_function_exit (basic_block); |
| |
| /* Recursive calls found in M_FUNC. */ |
| vec<gimple *> *m_calls; |
| /* Basic blocks already visited in the current function. */ |
| bitmap m_visited; |
| /* The current function. */ |
| function *m_func; |
| /* The current function code if it's (also) a built-in. */ |
| built_in_function m_built_in; |
| /* True if M_FUNC is a noreturn function. */ |
| bool noreturn_p; |
| }; |
| |
| /* Initialize the pass and its members. */ |
| |
| pass_warn_recursion::pass_warn_recursion (gcc::context *ctxt) |
| : gimple_opt_pass (warn_recursion_data, ctxt), |
| m_calls (), m_visited (), m_func (), m_built_in (), noreturn_p () |
| { |
| } |
| |
| /* Return true if there is path from BB to M_FUNC exit point along which |
| there is no (recursive) call to M_FUNC. */ |
| |
| bool |
| pass_warn_recursion::find_function_exit (basic_block bb) |
| { |
| if (!bitmap_set_bit (m_visited, bb->index)) |
| return false; |
| |
| if (bb == EXIT_BLOCK_PTR_FOR_FN (m_func)) |
| return true; |
| |
| /* Iterate over statements in BB, looking for a call to FNDECL. */ |
| for (auto si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next_nondebug (&si)) |
| { |
| gimple *stmt = gsi_stmt (si); |
| if (!is_gimple_call (stmt)) |
| continue; |
| |
| if (gimple_call_builtin_p (stmt, BUILT_IN_LONGJMP)) |
| /* A longjmp breaks infinite recursion. */ |
| return true; |
| |
| if (tree fndecl = gimple_call_fndecl (stmt)) |
| { |
| /* A throw statement breaks infinite recursion. */ |
| tree id = DECL_NAME (fndecl); |
| const char *name = IDENTIFIER_POINTER (id); |
| if (startswith (name, "__cxa_throw")) |
| return true; |
| /* As does a call to POSIX siglongjmp. */ |
| if (!strcmp (name, "siglongjmp")) |
| return true; |
| |
| if (m_built_in |
| && gimple_call_builtin_p (stmt, BUILT_IN_NORMAL) |
| && m_built_in == DECL_FUNCTION_CODE (fndecl)) |
| { |
| const char *cname |
| = IDENTIFIER_POINTER (DECL_NAME (current_function_decl)); |
| /* Don't warn about gnu_inline extern inline function |
| like strcpy calling __builtin_strcpy, that is fine, |
| if some call is made (the builtin isn't expanded inline), |
| a call is made to the external definition. */ |
| if (!(DECL_DECLARED_INLINE_P (current_function_decl) |
| && DECL_EXTERNAL (current_function_decl)) |
| || strcmp (name, cname) == 0) |
| { |
| /* The call is being made from the definition of a built-in |
| (e.g., in a replacement of one) to itself. */ |
| m_calls->safe_push (stmt); |
| return false; |
| } |
| } |
| } |
| |
| if (noreturn_p) |
| { |
| /* A noreturn call breaks infinite recursion. */ |
| int flags = gimple_call_flags (stmt); |
| if (flags & ECF_NORETURN) |
| return true; |
| } |
| |
| tree callee = gimple_call_fndecl (stmt); |
| if (!callee || m_func->decl != callee) |
| continue; |
| |
| /* Add the recursive call to the vector and return false. */ |
| m_calls->safe_push (stmt); |
| return false; |
| } |
| |
| /* If no call to FNDECL has been found search all BB's successors. */ |
| edge e; |
| edge_iterator ei; |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (find_function_exit (e->dest)) |
| return true; |
| |
| return false; |
| } |
| |
| |
| /* Search FUNC for unconditionally infinitely recursive calls to self |
| and issue a warning if it is such a function. */ |
| |
| unsigned int |
| pass_warn_recursion::execute (function *func) |
| { |
| auto_bitmap visited; |
| auto_vec<gimple *> calls; |
| |
| m_visited = visited; |
| m_calls = &calls; |
| m_func = func; |
| |
| /* Avoid diagnosing an apparently infinitely recursive function that |
| doesn't return where the infinite recursion might be avoided by |
| a call to another noreturn function. */ |
| noreturn_p = lookup_attribute ("noreturn", DECL_ATTRIBUTES (m_func->decl)); |
| |
| if (fndecl_built_in_p (m_func->decl, BUILT_IN_NORMAL)) |
| m_built_in = DECL_FUNCTION_CODE (m_func->decl); |
| else |
| m_built_in = BUILT_IN_NONE; |
| |
| basic_block entry_bb = ENTRY_BLOCK_PTR_FOR_FN (func); |
| |
| if (find_function_exit (entry_bb) || m_calls->length () == 0) |
| return 0; |
| |
| if (warning_at (DECL_SOURCE_LOCATION (func->decl), |
| OPT_Winfinite_recursion, |
| "infinite recursion detected")) |
| for (auto stmt: *m_calls) |
| { |
| location_t loc = gimple_location (stmt); |
| if (loc == UNKNOWN_LOCATION) |
| continue; |
| |
| inform (loc, "recursive call"); |
| } |
| |
| return 0; |
| } |
| |
| } // namespace |
| |
| gimple_opt_pass * |
| make_pass_warn_recursion (gcc::context *ctxt) |
| { |
| return new pass_warn_recursion (ctxt); |
| } |