cosmopolitan/libc/intrin/ftrace.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/atomic.h"
#include "libc/runtime/runtime.h"

/**
 * Function tracing enabled state.
 *
 * After ftrace_install() has been called, the logging of C function
 * calls may be controlled by changing this variable. If `__ftrace` is
 * greater than zero, functions are logged. Otherwise, they aren't.
 *
 * By convention, functions wishing to disable function tracing for a
 * short time period should say:
 *
 *     void foo() {
 *       ftrace_enabled(-1);
 *       bar();
 *       ftrace_enabled(+1);
 *     }
 *
 * This way you still have some flexibility to force function tracing,
 * by setting `__ftrace` to a higher number like `2` or `200`. Even
 * though under normal circumstances, `__ftrace` should only be either
 * zero or one.
 */
int __ftrace;