src/malloc_backtrace.cc

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#include "config.h"

#define THIS_IS_MALLOC_BACKTRACE_CC
#include "malloc_backtrace.h"

#include "thread_cache_ptr.h"

extern "C" {
  void* tc_new(size_t);
  void tc_delete(void*);
}

namespace tcmalloc {

// GrabBacktrace is the API to use when capturing backtrace for
// various tcmalloc features. It has optional emergency malloc
// integration for occasional case where stacktrace capturing method
// calls back to malloc (so we divert those calls to emergency malloc
// facility).
ATTRIBUTE_HIDDEN ATTRIBUTE_NOINLINE
int GrabBacktrace(void** result, int max_depth, int skip_count) {
  struct Args {
    void** result;
    int max_depth;
    int skip_count;
    int result_depth;
  } args;

  args.result = result;
  args.max_depth = max_depth;
  args.skip_count = skip_count;
  args.result_depth = 0;

  ThreadCachePtr::WithStacktraceScope(+[] (bool stacktrace_allowed, void* _args) {
    Args* args = static_cast<Args*>(_args);
    if (!stacktrace_allowed) {
      return;
    }

#if (!defined(NDEBUG) || defined(TCMALLOC_FORCE_BAD_TLS)) && defined(ENABLE_EMERGENCY_MALLOC)
    // Lets ensure test coverage of emergency malloc even in
    // configurations that otherwise don't exercise it.
    (tc_delete)(tc_new(32));
#endif

    args->result_depth = GetStackTrace(args->result, args->max_depth, args->skip_count + 2);
  }, &args);

  // Prevent tail calling WithStacktraceScope above
  return *const_cast<volatile int*>(&args.result_depth);
}

}  // namespace tcmalloc