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Diffstat (limited to 'gcc/gimple-warn-recursion.cc')
| -rw-r--r-- | gcc/gimple-warn-recursion.cc | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/gcc/gimple-warn-recursion.cc b/gcc/gimple-warn-recursion.cc new file mode 100644 index 0000000..3a50d5e --- /dev/null +++ b/gcc/gimple-warn-recursion.cc @@ -0,0 +1,202 @@ +/* -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: + virtual bool gate (function *) { return warn_infinite_recursion; } + + virtual unsigned int execute (function *); + + 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)) + { + /* 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); +} |