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/* An overview of the state machine from sm-malloc.cc.
Copyright (C) 2019-2021 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/>. */
/* Keep this in-sync with sm-malloc.cc */
digraph "malloc" {
/* STATES. */
/* Start state. */
start;
/* State for a pointer returned from malloc that hasn't been checked for
NULL.
It could be a pointer to heap-allocated memory, or could be NULL. */
unchecked;
/* State for a pointer that's known to be NULL. */
null;
/* State for a pointer to heap-allocated memory, known to be non-NULL. */
nonnull;
/* State for a pointer to freed memory. */
freed;
/* State for a pointer that's known to not be on the heap (e.g. to a local
or global). */
non_heap;
/* Stop state, for pointers we don't want to track any more. */
stop;
/* TRANSITIONS. */
start -> unchecked [label="on 'X=malloc(...);'"];
start -> unchecked [label="on 'X=calloc(...);'"];
start -> non_heap [label="on 'X=alloca(...);'"];
start -> non_heap [label="on 'X=__builtin_alloca(...);'"];
/* On "free". */
start -> freed [label="on 'free(X);'"];
unchecked -> freed [label="on 'free(X);'"];
nonnull -> freed [label="on 'free(X);'"];
freed -> stop [label="on 'free(X);':\n Warn('double-free')"];
non_heap -> stop [label="on 'free(X);':\n Warn('free of non-heap')"];
/* Handle "__attribute__((nonnull))". */
unchecked -> nonnull [label="on 'FN(X)' with __attribute__((nonnull)):\nWarn('possible NULL arg')"];
null -> stop [label="on 'FN(X)' with __attribute__((nonnull)):\nWarn('NULL arg')"];
/* is_zero_assignment. */
start -> null [label="on 'X = 0;'"];
unchecked -> null [label="on 'X = 0;'"];
nonnull -> null [label="on 'X = 0;'"];
freed -> null [label="on 'X = 0;'"];
start -> non_heap [label="on 'X = &EXPR;'"];
/* Handle dereferences. */
unchecked -> nonnull [label="on '*X':\nWarn('possible NULL deref')"];
null -> stop [label="on '*X':\nWarn('NULL deref')"];
freed -> stop [label="on '*X':\nWarn('use after free')"];
/* on_condition. */
unchecked -> nonnull [label="on 'X != 0'"];
unchecked -> null [label="on 'X == 0'"];
unchecked -> stop [label="on leak:\nWarn('leak')"];
nonnull -> stop [label="on leak:\nWarn('leak')"];
}
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