// Copyright (c) 2005 - 2007, Google Inc.

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//

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//

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// in the documentation and/or other materials provided with the

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//

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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

// Author: Arun Sharma

//

// Produce stack trace using libunwind

#include "utilities.h"

extern "C" {

#define UNW_LOCAL_ONLY

#include <libunwind.h>

}

#include "glog/raw_logging.h"

#include "stacktrace.h"

_START_GOOGLE_NAMESPACE_

// Sometimes, we can try to get a stack trace from within a stack

// trace, because libunwind can call mmap (maybe indirectly via an

// internal mmap based memory allocator), and that mmap gets trapped

// and causes a stack-trace request.  If were to try to honor that

// recursive request, we'd end up with infinite recursion or deadlock.

// Luckily, it's safe to ignore those subsequent traces.  In such

// cases, we return 0 to indicate the situation.

static bool g_now_entering = false;

// If you change this function, also change GetStackFrames below.

int GetStackTrace(void** result, int max_depth, int skip_count) {

  void *ip;

  int n = 0;

  unw_cursor_t cursor;

  unw_context_t uc;

  if (sync_val_compare_and_swap(&g_now_entering, false, true)) {

    return 0;

  }

  unw_getcontext(&uc);

  RAW_CHECK(unw_init_local(&cursor, &uc) >= 0, "unw_init_local failed");

  skip_count++;         // Do not include the "GetStackTrace" frame

  while (n < max_depth) {

    int ret = unw_get_reg(&cursor, UNW_REG_IP, (unw_word_t *) &ip);

    if (ret < 0)

      break;

    if (skip_count > 0) {

      skip_count--;

    } else {

      result[n++] = ip;

    }

    ret = unw_step(&cursor);

    if (ret <= 0)

      break;

  }

  g_now_entering = false;

  return n;

}

_END_GOOGLE_NAMESPACE_