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+/* A state machine for detecting misuses of <stdio.h>'s FILE * API.
+ Copyright (C) 2019-2020 Free Software Foundation, Inc.
+ Contributed by David Malcolm <dmalcolm@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 "tree.h"
+#include "function.h"
+#include "basic-block.h"
+#include "gimple.h"
+#include "options.h"
+#include "diagnostic-path.h"
+#include "diagnostic-metadata.h"
+#include "analyzer/analyzer.h"
+#include "analyzer/pending-diagnostic.h"
+#include "analyzer/sm.h"
+
+#if ENABLE_ANALYZER
+
+namespace {
+
+/* A state machine for detecting misuses of <stdio.h>'s FILE * API. */
+
+class fileptr_state_machine : public state_machine
+{
+public:
+ fileptr_state_machine (logger *logger);
+
+ bool inherited_state_p () const FINAL OVERRIDE { return false; }
+
+ bool on_stmt (sm_context *sm_ctxt,
+ const supernode *node,
+ const gimple *stmt) const FINAL OVERRIDE;
+
+ void on_condition (sm_context *sm_ctxt,
+ const supernode *node,
+ const gimple *stmt,
+ tree lhs,
+ enum tree_code op,
+ tree rhs) const FINAL OVERRIDE;
+
+ bool can_purge_p (state_t s) const FINAL OVERRIDE;
+ pending_diagnostic *on_leak (tree var) const FINAL OVERRIDE;
+
+ /* Start state. */
+ state_t m_start;
+
+ /* State for a FILE * returned from fopen that hasn't been checked for
+ NULL.
+ It could be an open stream, or could be NULL. */
+ state_t m_unchecked;
+
+ /* State for a FILE * that's known to be NULL. */
+ state_t m_null;
+
+ /* State for a FILE * that's known to be a non-NULL open stream. */
+ state_t m_nonnull;
+
+ /* State for a FILE * that's had fclose called on it. */
+ state_t m_closed;
+
+ /* Stop state, for a FILE * we don't want to track any more. */
+ state_t m_stop;
+};
+
+/* Base class for diagnostics relative to fileptr_state_machine. */
+
+class file_diagnostic : public pending_diagnostic
+{
+public:
+ file_diagnostic (const fileptr_state_machine &sm, tree arg)
+ : m_sm (sm), m_arg (arg)
+ {}
+
+ bool subclass_equal_p (const pending_diagnostic &base_other) const OVERRIDE
+ {
+ return m_arg == ((const file_diagnostic &)base_other).m_arg;
+ }
+
+ label_text describe_state_change (const evdesc::state_change &change)
+ OVERRIDE
+ {
+ if (change.m_old_state == m_sm.m_start
+ && change.m_new_state == m_sm.m_unchecked)
+ // TODO: verify that it's the fopen stmt, not a copy
+ return label_text::borrow ("opened here");
+ if (change.m_old_state == m_sm.m_unchecked
+ && change.m_new_state == m_sm.m_nonnull)
+ return change.formatted_print ("assuming %qE is non-NULL",
+ change.m_expr);
+ if (change.m_new_state == m_sm.m_null)
+ return change.formatted_print ("assuming %qE is NULL",
+ change.m_expr);
+ return label_text ();
+ }
+
+protected:
+ const fileptr_state_machine &m_sm;
+ tree m_arg;
+};
+
+class double_fclose : public file_diagnostic
+{
+public:
+ double_fclose (const fileptr_state_machine &sm, tree arg)
+ : file_diagnostic (sm, arg)
+ {}
+
+ const char *get_kind () const FINAL OVERRIDE { return "double_fclose"; }
+
+ bool emit (rich_location *rich_loc) FINAL OVERRIDE
+ {
+ return warning_at (rich_loc, OPT_Wanalyzer_double_fclose,
+ "double %<fclose%> of FILE %qE",
+ m_arg);
+ }
+
+ label_text describe_state_change (const evdesc::state_change &change)
+ OVERRIDE
+ {
+ if (change.m_new_state == m_sm.m_closed)
+ {
+ m_first_fclose_event = change.m_event_id;
+ return change.formatted_print ("first %qs here", "fclose");
+ }
+ return file_diagnostic::describe_state_change (change);
+ }
+
+ label_text describe_final_event (const evdesc::final_event &ev) FINAL OVERRIDE
+ {
+ if (m_first_fclose_event.known_p ())
+ return ev.formatted_print ("second %qs here; first %qs was at %@",
+ "fclose", "fclose",
+ &m_first_fclose_event);
+ return ev.formatted_print ("second %qs here", "fclose");
+ }
+
+private:
+ diagnostic_event_id_t m_first_fclose_event;
+};
+
+class file_leak : public file_diagnostic
+{
+public:
+ file_leak (const fileptr_state_machine &sm, tree arg)
+ : file_diagnostic (sm, arg)
+ {}
+
+ const char *get_kind () const FINAL OVERRIDE { return "file_leak"; }
+
+ bool emit (rich_location *rich_loc) FINAL OVERRIDE
+ {
+ diagnostic_metadata m;
+ /* CWE-775: "Missing Release of File Descriptor or Handle after
+ Effective Lifetime". */
+ m.add_cwe (775);
+ return warning_at (rich_loc, m, OPT_Wanalyzer_file_leak,
+ "leak of FILE %qE",
+ m_arg);
+ }
+
+ label_text describe_state_change (const evdesc::state_change &change)
+ FINAL OVERRIDE
+ {
+ if (change.m_new_state == m_sm.m_unchecked)
+ {
+ m_fopen_event = change.m_event_id;
+ return label_text::borrow ("opened here");
+ }
+ return file_diagnostic::describe_state_change (change);
+ }
+
+ label_text describe_final_event (const evdesc::final_event &ev) FINAL OVERRIDE
+ {
+ if (m_fopen_event.known_p ())
+ return ev.formatted_print ("%qE leaks here; was opened at %@",
+ ev.m_expr, &m_fopen_event);
+ else
+ return ev.formatted_print ("%qE leaks here", ev.m_expr);
+ }
+
+private:
+ diagnostic_event_id_t m_fopen_event;
+};
+
+/* fileptr_state_machine's ctor. */
+
+fileptr_state_machine::fileptr_state_machine (logger *logger)
+: state_machine ("file", logger)
+{
+ m_start = add_state ("start");
+ m_unchecked = add_state ("unchecked");
+ m_null = add_state ("null");
+ m_nonnull = add_state ("nonnull");
+ m_closed = add_state ("closed");
+ m_stop = add_state ("stop");
+}
+
+/* Implementation of state_machine::on_stmt vfunc for fileptr_state_machine. */
+
+bool
+fileptr_state_machine::on_stmt (sm_context *sm_ctxt,
+ const supernode *node,
+ const gimple *stmt) const
+{
+ if (const gcall *call = dyn_cast <const gcall *> (stmt))
+ if (tree callee_fndecl = sm_ctxt->get_fndecl_for_call (call))
+ {
+ if (is_named_call_p (callee_fndecl, "fopen", call, 2))
+ {
+ tree lhs = gimple_call_lhs (call);
+ if (lhs)
+ {
+ lhs = sm_ctxt->get_readable_tree (lhs);
+ sm_ctxt->on_transition (node, stmt, lhs, m_start, m_unchecked);
+ }
+ else
+ {
+ /* TODO: report leak. */
+ }
+ return true;
+ }
+
+ if (is_named_call_p (callee_fndecl, "fclose", call, 1))
+ {
+ tree arg = gimple_call_arg (call, 0);
+ arg = sm_ctxt->get_readable_tree (arg);
+
+ sm_ctxt->on_transition (node, stmt, arg, m_start, m_closed);
+
+ // TODO: is it safe to call fclose (NULL) ?
+ sm_ctxt->on_transition (node, stmt, arg, m_unchecked, m_closed);
+ sm_ctxt->on_transition (node, stmt, arg, m_null, m_closed);
+
+ sm_ctxt->on_transition (node, stmt , arg, m_nonnull, m_closed);
+
+ sm_ctxt->warn_for_state (node, stmt, arg, m_closed,
+ new double_fclose (*this, arg));
+ sm_ctxt->on_transition (node, stmt, arg, m_closed, m_stop);
+ return true;
+ }
+
+ // TODO: operations on closed file
+ // etc
+ }
+
+ return false;
+}
+
+/* Implementation of state_machine::on_condition vfunc for
+ fileptr_state_machine.
+ Potentially transition state 'unchecked' to 'nonnull' or to 'null'. */
+
+void
+fileptr_state_machine::on_condition (sm_context *sm_ctxt,
+ const supernode *node,
+ const gimple *stmt,
+ tree lhs,
+ enum tree_code op,
+ tree rhs) const
+{
+ if (!zerop (rhs))
+ return;
+
+ // TODO: has to be a FILE *, specifically
+ if (TREE_CODE (TREE_TYPE (lhs)) != POINTER_TYPE)
+ return;
+
+ // TODO: has to be a FILE *, specifically
+ if (TREE_CODE (TREE_TYPE (rhs)) != POINTER_TYPE)
+ return;
+
+ if (op == NE_EXPR)
+ {
+ log ("got 'ARG != 0' match");
+ sm_ctxt->on_transition (node, stmt,
+ lhs, m_unchecked, m_nonnull);
+ }
+ else if (op == EQ_EXPR)
+ {
+ log ("got 'ARG == 0' match");
+ sm_ctxt->on_transition (node, stmt,
+ lhs, m_unchecked, m_null);
+ }
+}
+
+/* Implementation of state_machine::can_purge_p vfunc for fileptr_state_machine.
+ Don't allow purging of pointers in state 'unchecked' or 'nonnull'
+ (to avoid false leak reports). */
+
+bool
+fileptr_state_machine::can_purge_p (state_t s) const
+{
+ return s != m_unchecked && s != m_nonnull;
+}
+
+/* Implementation of state_machine::on_leak vfunc for
+ fileptr_state_machine, for complaining about leaks of FILE * in
+ state 'unchecked' and 'nonnull'. */
+
+pending_diagnostic *
+fileptr_state_machine::on_leak (tree var) const
+{
+ return new file_leak (*this, var);
+}
+
+} // anonymous namespace
+
+/* Internal interface to this file. */
+
+state_machine *
+make_fileptr_state_machine (logger *logger)
+{
+ return new fileptr_state_machine (logger);
+}
+
+#endif /* #if ENABLE_ANALYZER */