Android系统定制/测试(Crash/ANR等Bug/性能分析必备技巧)
Android中打印堆栈的几种方法
public void ThrowException() {//调试打印堆栈而不退出Log.d(TAG, Log.getStackTraceString(new Throwable()));//创建异常打印堆栈Exception e = new Exception("this is a log");e.printStackTrace();//获取当前线程的堆栈for (StackTraceElement i : Thread.currentThread().getStackTrace()) {Log.i(TAG, i.toString());}RuntimeException re = new RuntimeException();re.fillInStackTrace();Log.i(TAG, "stackTrace", re);//主动抛出异常调试try {Log.i(TAG, "---NullPointerException---start);throw new NullPointerException();} catch (NullPointerException e1) {//TODO: handle exceptionLog.i(TAG, "---NullPointerException---");Log.e(TAG, Log.getStackTraceString(e1));//e1.printStackTrace();}Log.i(TAG, "---NullPointerException---end");}
C++代码中打印堆栈
C++也是支持异常处理的，异常处理库中，已经包含了获取backtrace的接口，Android也是利用这个接口来打印堆栈信息的。在Android的C++中，已经集成了一个工具类CallStack，在libutils.so中
CallStack stack;stack.update();stack.dump();
void dumping_callstack(){android::CallStack stack;//getpid()和gettid()效果一样//stack.update(2,getpid());//stack.update(2,gettid());stack.update();//输出到printfstack.dump(1);//输出到logcatstack.log("dump_test");//可以设置第2、3个参数//stack.log("Dumping Stack", ANDROID_LOG_ERROR, "test");}
在Android4.1.1以上，如Android4.4.4，使用Android系统自带的libcorkscrew.so
在Android5.0及以上，Android系统中没有了libcorkscrew.so，使用本身编译的libunwind
http://androidxref.com/4.4.4_r1/xref/system/core/libcorkscrew/
Android5.0至Android12，使用Android系统自带的libbacktrace.so，如下所示
http://androidxref.com/5.0.0_r2/xref/system/core/libbacktrace/
http://aospxref.com/android-7.1.2_r39/xref/system/core/libbacktrace/
http://aospxref.com/android-12.0.0_r3/xref/system/unwinding/libbacktrace/
C代码中打印堆栈
C代码，尤其是底层C库，想要看到调用的堆栈信息，还是比较麻烦的。
CallStack肯定是不能用
一是因为其是C++写的，需要重新封装才能在C中使用
二是底层库反调上层库的函数，会造成链接器循环依赖而无法链接。不过也不是没有办法，可以通过android工具类CallStack实现中使用的unwind调用及符号解析函数来处理。
需要注意的是，为解决链接问题，最好使用dlopen方式，查找需要用到的接口再直接调用，这样会比较简单。如下为相关的实现代码，只需要在要打印的文件中插入此部分代码，然后调用getCallStack()即可，无需包含太多的头文件和修改Android.mk文件
typedef ssize_t (*unwindFn)(backtrace_frame_t*, size_t, size_t);typedef void (*unwindSymbFn)(const backtrace_frame_t*, size_t, backtrace_symbol_t*);typedef void (*unwindSymbFreeFn)(backtrace_symbol_t*, size_t);static void *gHandle = NULL;static int getCallStack(void){ssize_t i = 0;ssize_t result = 0;ssize_t count;backtrace_frame_t mStack[MAX_DEPTH];backtrace_symbol_t symbols[MAX_DEPTH];unwindFn unwind_backtrace = NULL;unwindSymbFn get_backtrace_symbols = NULL;unwindSymbFreeFn free_backtrace_symbols = NULL;// open the so.if(gHandle == NULL) gHandle = dlopen(PATH, RTLD_NOW);// get the interface for unwind and symbol analyseif(gHandle != NULL) unwind_backtrace = (unwindFn)dlsym(gHandle, "unwind_backtrace");if(gHandle != NULL) get_backtrace_symbols = (unwindSymbFn)dlsym(gHandle, "get_backtrace_symbols");if(gHandle != NULL) free_backtrace_symbols = (unwindSymbFreeFn)dlsym(gHandle, "free_backtrace_symbols");if(!gHandle ||!unwind_backtrace ||!get_backtrace_symbols || !free_backtrace_symbols ){ALOGE("Error! cannot get unwind info: handle:%p %p %p %p",gHandle, unwind_backtrace, get_backtrace_symbols, free_backtrace_symbols );return result;}count= unwind_backtrace(mStack, 1, MAX_DEPTH);get_backtrace_symbols(mStack, count, symbols);for (i = 0; i < count; i++) {char line[MAX_BACKTRACE_LINE_LENGTH];const char* mapName = symbols[i].map_name ? symbols[i].map_name : "<unknown>";const char* symbolName =symbols[i].demangled_name ? symbols[i].demangled_name : symbols[i].symbol_name;size_t fieldWidth = (MAX_BACKTRACE_LINE_LENGTH - 80) / 2;if (symbolName) {uint32_t pc_offset = symbols[i].relative_pc - symbols[i].relative_symbol_addr;if (pc_offset) {snprintf(line, MAX_BACKTRACE_LINE_LENGTH, "#%02d pc %08x %.*s (%.*s+%u)",i, symbols[i].relative_pc, fieldWidth, mapName,fieldWidth, symbolName, pc_offset);} else {snprintf(line, MAX_BACKTRACE_LINE_LENGTH, "#%02d pc %08x %.*s (%.*s)",i, symbols[i].relative_pc, fieldWidth, mapName,fieldWidth, symbolName);}} else {snprintf(line, MAX_BACKTRACE_LINE_LENGTH, "#%02d pc %08x %.*s",i, symbols[i].relative_pc, fieldWidth, mapName);}ALOGD("%s", line);}free_backtrace_symbols(symbols, count);return result;}
extern "C" void dumping_callstack();void dumping_callstack(){android::CallStack stack;stack.update();stack.log(“dump_test“);}
Kernel代码中打印堆栈
#include <asm/ptrace.h>printk(KERN_ERR "dump_stack start: %s() %d n",__FUNCTION__,__LINE__);dump_stack();printk(KERN_ERR "dump_stack stop: %s() %d n",__FUNCTION__,__LINE__);
native crash所对应的java层堆栈
crash线程就是捕获到信号的线程，虽然这在SIGABRT下不必定可靠，在信号处理函数中得到当前线程的名字，而后把crash线程的名字传给java层，在java里dump出这个线程的堆栈，就是crash所对应的java层堆栈
在C中得到线程名字
char* getThreadName(pid_t tid) {if (tid <= 1) {return NULL;}char* path = (char *) calloc(1, 80);char* line = (char *) calloc(1, THREAD_NAME_LENGTH);snprintf(path, PATH_MAX, "proc/%d/comm", tid);FILE* commFile = NULL;if (commFile = fopen(path, "r")) {fgets(line, THREAD_NAME_LENGTH, commFile);fclose(commFile);}free(path);if (line) {int length = strlen(line);if (line[length - 1] == 'n') {line[length - 1] = '';}}return line;}
然后传给Java层
/*** 根据线程名得到线程对象，native层会调用该方法，不能混淆* @param threadName* @return*/public static Thread getThreadByName(String threadName) {if (TextUtils.isEmpty(threadName)) {return null;}Set<Thread> threadSet = Thread.getAllStackTraces().keySet();Thread[] threadArray = threadSet.toArray(new Thread[threadSet.size()]);Thread theThread = null;for(Thread thread : threadArray) {if (thread.getName().equals(threadName)) {theThread = thread;}}Log.d(TAG, "threadName: " + threadName + ", thread: " + theThread);return theThread;}
参考链接
https://github.com/chenxumeng/NativeCrashhttps://github.com/xroche/coffeecatchhttps://github.com/iqiyi/xCrashhttps://github.com/hexhacking/xCrashhttp://www.javashuo.com/article/p-kkmrvyow-dq.htmlhttp://www.javashuo.com/article/p-agyiphwq-ws.html
http://aospxref.com/http://androidxref.com
原文始发于微信公众号（哆啦安全）：Android/C/C++/Native打印堆栈的方法
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