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// 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 libgcc

#include <unwind.h>  // ABI defined unwinder

#include "stacktrace.h"

namespace google {
inline namespace glog_internal_namespace_ {

struct trace_arg_t {
  void** result;
  int max_depth;
  int skip_count;
  int count;
};

// Workaround for the malloc() in _Unwind_Backtrace() issue.
static _Unwind_Reason_Code nop_backtrace(struct _Unwind_Context* /*uc*/,
                                         void* /*opq*/) {
  return _URC_NO_REASON;
}

// This code is not considered ready to run until
// static initializers run so that we are guaranteed
// that any malloc-related initialization is done.
static bool ready_to_run = false;
class StackTraceInit {
 public:
  StackTraceInit() {
    // Extra call to force initialization
    _Unwind_Backtrace(nop_backtrace, nullptr);
    ready_to_run = true;
  }
};

static StackTraceInit module_initializer;  // Force initialization

static _Unwind_Reason_Code GetOneFrame(struct _Unwind_Context* uc, void* opq) {
  auto* targ = static_cast<trace_arg_t*>(opq);

  if (targ->skip_count > 0) {
    targ->skip_count--;
  } else {
    targ->result[targ->count++] = reinterpret_cast<void*>(_Unwind_GetIP(uc));
  }

  if (targ->count == targ->max_depth) {
    return _URC_END_OF_STACK;
  }

  return _URC_NO_REASON;
}

// If you change this function, also change GetStackFrames below.
int GetStackTrace(void** result, int max_depth, int skip_count) {
  if (!ready_to_run) {
    return 0;
  }

  trace_arg_t targ;

  skip_count += 1;  // Do not include the "GetStackTrace" frame

  targ.result = result;
  targ.max_depth = max_depth;
  targ.skip_count = skip_count;
  targ.count = 0;

  _Unwind_Backtrace(GetOneFrame, &targ);

  return targ.count;
}

}  // namespace glog_internal_namespace_
}  // namespace google