每天进步一点点——Linux系统中的异常堆栈跟踪简单实现
int backtrace (void **buffer, int size);
该函数用来获取当前线程的调用堆栈,获取的信息将会被存放在buffer中,它是一个指针数组。参数size用来指定buffer中可以保存多少个void* 元素。函数返回值是实际获取的指针个数,最大不超过size大小在buffer中的指针实际是从堆栈中获取的返回地址,每一个堆栈框架有一个返回地址。注意某些编译器的优化选项对获取正确的调用堆栈有干扰,另外内联函数没有堆栈框架;删除框架指针也会使无法正确解析堆栈内容。
char **backtrace_symbols (void *const *buffer, int size);
该函数将从backtrace函数获取的信息转化为一个字符串数组。参数buffer是从backtrace函数获取的数组指针,size是该数组中的元素个数(backtrace的返回值),函数返回值是一个指向字符串数组的指针,它的大小同buffer相同。每个字符串包含了一个相对于buffer中对应元素的可打印信息。它包括函数名,函数的偏移地址和实际的返回地址。backtrace_symbols生成的字符串都是malloc出来的,但是不要最后一个一个的free,因为backtrace_symbols会根据backtrace给出的callstack层数,一次性的将malloc出来一块内存释放,所以,只需要在最后free返回指针就OK了。
void backtrace_symbols_fd (void *const *buffer, int size, int fd);该函数与backtrace_symbols函数具有相同的功能,不同的是它不会给调用者返回字符串数组,而是将结果写入文件描述符为fd的文件中,每个函数对应一行。它不需要调用malloc函数,因此适用于有可能调用该函数会失败的情况。
/** * 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; } } }
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