/**
* 用于将backtrace_symbols函数所返回的字符串解析成对应的函数名，便于理解
* 头文件  cxxabi.h
* 名字空间	abi
* @param mangled_name A NUL-terminated character string containing the name to be demangled.
* @param output_buffer  A region of memory, allocated with malloc, of *length bytes, into which the demangled name is stored. If output_buffer is not long enough, it is expanded using realloc. 
*     output_buffer may instead be NULL; in that case, the demangled name is placed in a region of memory allocated with malloc. 
* @param length  If length is non-NULL, the length of the buffer containing the demangled name is placed in *length.
* @param status  *status is set to one of the following values:
*        0: The demangling operation succeeded.
*       -1: A memory allocation failiure occurred.
*       -2: Mangled_name is not a valid name under the C++ ABI mangling rules.
*       -3: One of the arguments is invalid.
*/
char *__cxa_demangle (const char *mangled_name, char *output_buffer, size_t *length, int *status);

#define MAX_FRAMES 100
void GetStackTrace (std::string* stack)
{
  void* addresses[MAX_FRAMES];
  int size = backtrace (addresses, MAX_FRAMES);
  std::unique_ptr<char*, void(*)(void*)> symbols {
    backtrace_symbols (addresses, size),
    std::free
  };
  for (int i = 0; i < size; ++i) {
    stack->append (symbols.get()[i]);
    stack->append ("\n");
  }
}

void TestFunc (std::string& stack, int value)
{
  while (--value);
  GetStackTrace (&stack);
}
int main(int argc, char* argv[])
{
  std::string stack;
  TestFunc (stack, 5);
  std::cout << stack << std::endl;
  return 0;
}

void DemangleSymbol (std::string* symbol)
{
  size_t size = 0;
  int status = -4;
  char temp[256] = {'\0'};
  //first, try to demangle a c++ name
  if (1 == sscanf (symbol->c_str (), "%*[^(]%*[^_]%[^)+]", temp)) {
    std::unique_ptr<char, void(*)(void*)> demangled {
      abi::__cxa_demangle (temp, NULL, &size, &status),
      std::free
    };
    if (demangled.get ()) {
      symbol->clear ();
      symbol->append (demangled.get ());
      return;
    }
  }
  //if that didn't work, try to get a regular c symbol
  if (1 == sscanf(symbol->c_str (), "%255s", temp)) {
    symbol->clear ();
    symbol->append (temp);
  }
}

void GetStackTrace (std::string* stack)
{
  void* addresses[MAX_FRAMES];
  int size = backtrace (addresses, MAX_FRAMES);
  std::unique_ptr<char*, void(*)(void*)> symbols {
    backtrace_symbols (addresses, size),
    std::free
  };
  for (int i = 0; i < size; ++i) {
    std::string demangled (symbols.get()[i]);
    DemangleSymbol (&demangled);
    stack->append (demangled);
    stack->append ("\n");
  }
}

// The prefix used for mangled symbols, per the Itanium C++ ABI:
// http://www.codesourcery.com/cxx-abi/abi.html#mangling
const char kMangledSymbolPrefix[] = "_Z";
// Characters that can be used for symbols, generated by Ruby:
// (('a'..'z').to_a+('A'..'Z').to_a+('0'..'9').to_a + ['_']).join
const char kSymbolCharacters[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_";
// Demangles C++ symbols in the given text. Example:
// "out/Debug/base_unittests(_ZN10StackTraceC1Ev+0x20) [0x817778c]"
// =>
// "out/Debug/base_unittests(StackTrace::StackTrace()+0x20) [0x817778c]"
void DemangleSymbol (std::string* symbol)
{
  std::string::size_type search_from = 0;
  while (search_from < symbol->size ()) {
    // Look for the start of a mangled symbol from search_from
    std::string::size_type mangled_start = symbol->find (kMangledSymbolPrefix, search_from);
    if (mangled_start == std::string::npos) {
      break; // Mangled symbol not found
    }
    // Look for the end of the mangled symbol
    std::string::size_type mangled_end = symbol->find_first_not_of (kSymbolCharacters, mangled_start);
    if (mangled_end == std::string::npos) {
      mangled_end = symbol->size ();
    }
    std::string mangled_symbol = std::move (symbol->substr (mangled_start, mangled_end - mangled_start));
    // Try to demangle the mangled symbol candidate
    int status = -4; // some arbitrary value to eliminate the compiler warning
    std::unique_ptr<char, void(*)(void*)> demangled_symbol {
      abi::__cxa_demangle (mangled_symbol.c_str (), nullptr, 0, &status),
      std::free
    };
    // 0 Demangling is success
    if (0 == status) {
      // Remove the mangled symbol
      symbol->erase (mangled_start, mangled_end - mangled_start);
      // Insert the demangled symbol
      symbol->insert (mangled_start, demangled_symbol.get ());
      // Next time, we will start right after the demangled symbol
      search_from = mangled_start + strlen (demangled_symbol.get ());
    }
    else {
      // Failed to demangle. Retry after the "_Z" we just found
      search_from = mangled_start + 2;
    }
  }
}