本文用纯c的代码，实现异常捕获try-catch组件。阅读本文需要时刻牢记setjmp和longjmp的对应关系。
在java，python，c++里面都有try catch异常捕获。在try代码块里面执行的函数，如果出错有异常了，就会throw把异常抛出来，抛出来的异常被catch接收进行处理，而finally意味着无论有没有异常，都会执行finally代码块内的代码。
try{ connect_sql();//throw}catch(){}finally { };关于跳转，有两个跳转。那么在这里我们必然选用长跳转。
setjmp/longjmp这两个函数是不存在压栈出栈的，也就是说longjmp跳转到setjmp的地方后，会覆盖之前的栈。
#include #include jmp_buf env;int count = 0;void sub_func(int idx) { printf("sub_func -->idx : %d
", idx); //第二个参数就是setjmp()的返回值 longjmp(env, idx);}int main() { int idx = 0; //设置跳转标签，第一次返回0 count = setjmp(env); if (count == 0) { printf("count : %d
", count); sub_func(++idx); } else if (count == 1) { printf("count : %d
", count); sub_func(++idx); } else if (count == 2) { printf("count : %d
", count); sub_func(++idx); } else { printf("other count
"); } return 0;} count : 0sub_func -->idx : 1count : 1sub_func -->idx : 2count : 2sub_func -->idx : 3other count try ---> setjmp(env)throw ---> longjmp(env,Exception)catch(Exception)我们其实可以分析出来，setjmp和count==0的地方，相当于try，后面的else if 相当于catch，最后一个else，其实并不是finally，因为finally是不管怎么样都会执行，上图我标注的其实是误导的。应该是下图这样才对。
宏定义实现try-catch Demo
4个关键字分析出来它们的关系之后，其实我们就能用宏定义来实现了。
#include #include typedef struct _Exception { jmp_buf env; int exceptype;} Exception;#define Try(excep) if((excep.exceptype=setjmp(excep.env))==0)#define Catch(excep, ExcepType) else if(excep.exceptype==ExcepType)#define Throw(excep, ExcepType) longjmp(excep.env,ExcepType)#define Finallyvoid throw_func(Exception ex, int idx) { printf("throw_func -->idx : %d
", idx); Throw(ex, idx);}int main() { int idx = 0; Exception ex; Try(ex) { printf("ex.exceptype : %d
", ex.exceptype); throw_func(ex, ++idx); } Catch(ex, 1) { printf("ex.exceptype : %d
", ex.exceptype); } Catch(ex, 2) { printf("ex.exceptype : %d
", ex.exceptype); } Catch(ex, 3) { printf("ex.exceptype : %d
", ex.exceptype); } Finally{ printf("Finally
"); }; return 0;} ex.exceptype : 0throw_func -->idx : 1ex.exceptype : 1Finally相关视频推荐
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虽然现在demo版看起来像这么回事了，但是还是有两个问题：
系统提供了三个宏可以供我们使用，如果我们没有catch到异常，我们就可以打印出来
__func__, __FILE__, __LINE__我们知道try-catch是可以嵌套的，那么这就形成了一个栈的数据结构，现在下面有三个try，每个setjmp对应的都是不同的jmp_buf,那么我们可以定义一个jmp_buf的栈。
try{ try{ try{ }catch(){ } }catch(){ }}catch(){}finally{};那么我们很容易能写出来，既然是栈，try的时候我们就插入一个结点，catch的时候我们就pop一个出来。
#define EXCEPTION_MESSAGE_LENGTH 512typedef struct _ntyException { const char *name;} ntyException;ntyException SQLException = {"SQLException"};ntyException TimeoutException = {"TimeoutException"};typedef struct _ntyExceptionFrame { jmp_buf env; int line; const char *func; const char *file; ntyException *exception; struct _ntyExceptionFrame *next; char message[EXCEPTION_MESSAGE_LENGTH + 1];} ntyExceptionFrame;enum { ExceptionEntered = 0,//0 ExceptionThrown, //1 ExceptionHandled, //2 ExceptionFinalized//3};每个线程都可以try-catch，但是我们以及知道了是个栈结构，既ExceptionStack，那么每个线程是独有一个ExceptionStack呢？还是共享同一个ExceptionStack？很明显，A线程的异常应该有A的处理，而不是由B线程处理。
/* ** **** ******** **************** Thread safety **************** ******** **** ** */#define ntyThreadLocalData pthread_key_t#define ntyThreadLocalDataSet(key, value) pthread_setspecific((key), (value))#define ntyThreadLocalDataGet(key) pthread_getspecific((key))#define ntyThreadLocalDataCreate(key) pthread_key_create(&(key), NULL)ntyThreadLocalData ExceptionStack;static void init_once(void) { ntyThreadLocalDataCreate(ExceptionStack);}static pthread_once_t once_control = PTHREAD_ONCE_INIT;void ntyExceptionInit(void) { pthread_once(&once_control, init_once);}首先创建一个新节点入栈，然后setjmp设置一个标记，接下来就是大括号里面的操作了，如果有异常，那么就会被throw抛出来，为什么这里最后一行是if？因为longjmp的时候，返回的地方是setjmp，不要忘了！要时刻扣住longjmp和setjmp。
#define Try do { \ volatile int Exception_flag; \ ntyExceptionFrame frame; \ frame.message[0] = 0; \ frame.next = (ntyExceptionFrame*)ntyThreadLocalDataGet(ExceptionStack); \ ntyThreadLocalDataSet(ExceptionStack, &frame); \ Exception_flag = setjmp(frame.env); \ if (Exception_flag == ExceptionEntered) {Try{//... Throw(A, "A");}在这里，我们不应该把throw定义成宏，而应该定义成函数。这里分两类，一类是try里面的throw，一类是没有try直接throw。
这里的##__VA_ARGS__是可变参数，具体不多介绍了，不是本文重点。
#define ReThrow ntyExceptionThrow(frame.exception, frame.func, frame.file, frame.line, NULL)#define Throw(e, cause, ...) ntyExceptionThrow(&(e), __func__, __FILE__, __LINE__, cause, ##__VA_ARGS__,NULL)void ntyExceptionThrow(ntyException *excep, const char *func, const char *file, int line, const char *cause, ...) { va_list ap; ntyExceptionFrame *frame = (ntyExceptionFrame *) ntyThreadLocalDataGet(ExceptionStack); if (frame) { //异常名 frame->exception = excep; frame->func = func; frame->file = file; frame->line = line; //异常打印的信息 if (cause) { va_start(ap, cause); vsnprintf(frame->message, EXCEPTION_MESSAGE_LENGTH, cause, ap); va_end(ap); } ntyExceptionPopStack; longjmp(frame->env, ExceptionThrown); } //没有被catch,直接throw else if (cause) { char message[EXCEPTION_MESSAGE_LENGTH + 1]; va_start(ap, cause); vsnprintf(message, EXCEPTION_MESSAGE_LENGTH, cause, ap); va_end(ap); printf("%s: %s
raised in %s at %s:%d
", excep->name, message, func ? func : "?", file ? file : "?", line); } else { printf("%s: %p
raised in %s at %s:%d
", excep->name, excep, func ? func : "?", file ? file : "?", line); }}如果还是ExceptionEntered状态，说明没有异常，没有throw。如果捕获到异常了，那么其状态就是ExceptionHandled。
#define Catch(nty_exception) \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } else if (frame.exception == &(nty_exception)) { \ Exception_flag = ExceptionHandled;finally也是一样，如果还是ExceptionEntered状态，说明没有异常没有捕获，那么现在状态是终止阶段。
#define Finally \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } { \ if (Exception_flag == ExceptionEntered) \ Exception_flag = ExceptionFinalized;有些人看到EndTry可能会有疑问，try-catch一共不就4个关键字吗？怎么你多了一个。我们先来看看EndTry做了什么，首先如果是ExceptionEntered状态，那意味着什么？意味着没有throw，没有catch，没有finally，只有try，我们需要对这种情况进行处理，要出栈。还有一种情况，如果是ExceptionThrown状态，说明什么？没有被catch捕获到，那么我们就再次抛出，进行打印错误。至于为什么多个EndTry，写起来方便呗~
#define EndTry \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } if (Exception_flag == ExceptionThrown) {ReThrow;} \ } while (0)/* ** **** ******** **************** try / catch / finally / throw **************** ******** **** ** */#define EXCEPTION_MESSAGE_LENGTH 512typedef struct _ntyException { const char *name;} ntyException;ntyException SQLException = {"SQLException"};ntyException TimeoutException = {"TimeoutException"};typedef struct _ntyExceptionFrame { jmp_buf env; int line; const char *func; const char *file; ntyException *exception; struct _ntyExceptionFrame *next; char message[EXCEPTION_MESSAGE_LENGTH + 1];} ntyExceptionFrame;enum { ExceptionEntered = 0,//0 ExceptionThrown, //1 ExceptionHandled, //2 ExceptionFinalized//3};#define ntyExceptionPopStack \ ntyThreadLocalDataSet(ExceptionStack, ((ntyExceptionFrame*)ntyThreadLocalDataGet(ExceptionStack))->next)#define ReThrow ntyExceptionThrow(frame.exception, frame.func, frame.file, frame.line, NULL)#define Throw(e, cause, ...) ntyExceptionThrow(&(e), __func__, __FILE__, __LINE__, cause, ##__VA_ARGS__,NULL)#define Try do { \ volatile int Exception_flag; \ ntyExceptionFrame frame; \ frame.message[0] = 0; \ frame.next = (ntyExceptionFrame*)ntyThreadLocalDataGet(ExceptionStack); \ ntyThreadLocalDataSet(ExceptionStack, &frame); \ Exception_flag = setjmp(frame.env); \ if (Exception_flag == ExceptionEntered) {#define Catch(nty_exception) \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } else if (frame.exception == &(nty_exception)) { \ Exception_flag = ExceptionHandled;#define Finally \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } { \ if (Exception_flag == ExceptionEntered) \ Exception_flag = ExceptionFinalized;#define EndTry \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } if (Exception_flag == ExceptionThrown) {ReThrow;} \ } while (0)void ntyExceptionThrow(ntyException *excep, const char *func, const char *file, int line, const char *cause, ...) { va_list ap; ntyExceptionFrame *frame = (ntyExceptionFrame *) ntyThreadLocalDataGet(ExceptionStack); if (frame) { //异常名 frame->exception = excep; frame->func = func; frame->file = file; frame->line = line; //异常打印的信息 if (cause) { va_start(ap, cause); vsnprintf(frame->message, EXCEPTION_MESSAGE_LENGTH, cause, ap); va_end(ap); } ntyExceptionPopStack; longjmp(frame->env, ExceptionThrown); } //没有被catch,直接throw else if (cause) { char message[EXCEPTION_MESSAGE_LENGTH + 1]; va_start(ap, cause); vsnprintf(message, EXCEPTION_MESSAGE_LENGTH, cause, ap); va_end(ap); printf("%s: %s
raised in %s at %s:%d
", excep->name, message, func ? func : "?", file ? file : "?", line); } else { printf("%s: %p
raised in %s at %s:%d
", excep->name, excep, func ? func : "?", file ? file : "?", line); }}/* ** **** ******** **************** debug **************** ******** **** ** */ntyException A = {"AException"};ntyException B = {"BException"};ntyException C = {"CException"};ntyException D = {"DException"};void *thread(void *args) { pthread_t selfid = pthread_self(); Try { Throw(A, "A"); } Catch (A) { printf("catch A : %ld
", selfid); } EndTry; Try { Throw(B, "B"); } Catch (B) { printf("catch B : %ld
", selfid); } EndTry; Try { Throw(C, "C"); } Catch (C) { printf("catch C : %ld
", selfid); } EndTry; Try { Throw(D, "D"); } Catch (D) { printf("catch D : %ld
", selfid); } EndTry; Try { Throw(A, "A Again"); Throw(B, "B Again"); Throw(C, "C Again"); Throw(D, "D Again"); } Catch (A) { printf("catch A again : %ld
", selfid); } Catch (B) { printf("catch B again : %ld
", selfid); } Catch (C) { printf("catch C again : %ld
", selfid); } Catch (D) { printf("catch B again : %ld
", selfid); } EndTry;}#define PTHREAD_NUM 8int main(void) { ntyExceptionInit(); printf("
=> Test1: Throw
"); { Throw(D, NULL); //ntyExceptionThrow(&(D), "_function_name_", "_file_name_", 202, ((void *) 0), ((void *) 0)) Throw(C, "null C"); //ntyExceptionThrow(&(C), "_function_name_", "_file_name_", 203, "null C", ((void *) 0)) } printf("=> Test1: Ok
"); printf("
=> Test2: Try-Catch Double Nesting
"); { Try { Try { Throw(B, "call B"); } Catch (B) { printf("catch B
"); } EndTry; Throw(A, NULL); } Catch(A) { printf("catch A
"); printf("Result: Ok
"); } EndTry; } printf("=> Test2: Ok
"); printf("
=> Test3: Try-Catch Triple Nesting
"); { Try { Try { Try { Throw(C, "call C"); } Catch (C) { printf("catch C
"); } EndTry; Throw(B, "call B"); } Catch (B) { printf("catch B
"); } EndTry; Throw(A, NULL); } Catch(A) { printf("catch A
"); } EndTry; } printf("=> Test3: Ok
"); printf("=> Test4: Test Thread-safeness
"); int i = 0; pthread_t th_id[PTHREAD_NUM]; for (i = 0; i < PTHREAD_NUM; i++) { pthread_create(&th_id[i], NULL, thread, NULL); } for (i = 0; i < PTHREAD_NUM; i++) { pthread_join(th_id[i], NULL); } printf("=> Test4: Ok
"); printf("
=> Test5: No Success Catch
"); { Try { Throw(A, "no catch A ,should Rethrow"); } EndTry; } printf("=> Test5: Rethrow Success
"); printf("
=> Test6: Normal Test
"); { Try { Throw(A, "call A"); } Catch(A) { printf("catch A
"); } Finally { printf("wxf nb
"); }; EndTry; } printf("=> Test6: ok
");}#include #include #include #include /* ** **** ******** **************** Thread safety **************** ******** **** ** */#define ntyThreadLocalData pthread_key_t#define ntyThreadLocalDataSet(key, value) pthread_setspecific((key), (value))#define ntyThreadLocalDataGet(key) pthread_getspecific((key))#define ntyThreadLocalDataCreate(key) pthread_key_create(&(key), NULL)ntyThreadLocalData ExceptionStack;static void init_once(void) { ntyThreadLocalDataCreate(ExceptionStack);}static pthread_once_t once_control = PTHREAD_ONCE_INIT;void ntyExceptionInit(void) { pthread_once(&once_control, init_once);}/* ** **** ******** **************** try / catch / finally / throw **************** ******** **** ** */#define EXCEPTION_MESSAGE_LENGTH 512typedef struct _ntyException { const char *name;} ntyException;ntyException SQLException = {"SQLException"};ntyException TimeoutException = {"TimeoutException"};typedef struct _ntyExceptionFrame { jmp_buf env; int line; const char *func; const char *file; ntyException *exception; struct _ntyExceptionFrame *next; char message[EXCEPTION_MESSAGE_LENGTH + 1];} ntyExceptionFrame;enum { ExceptionEntered = 0,//0 ExceptionThrown, //1 ExceptionHandled, //2 ExceptionFinalized//3};#define ntyExceptionPopStack \ ntyThreadLocalDataSet(ExceptionStack, ((ntyExceptionFrame*)ntyThreadLocalDataGet(ExceptionStack))->next)#define ReThrow ntyExceptionThrow(frame.exception, frame.func, frame.file, frame.line, NULL)#define Throw(e, cause, ...) ntyExceptionThrow(&(e), __func__, __FILE__, __LINE__, cause, ##__VA_ARGS__,NULL)#define Try do { \ volatile int Exception_flag; \ ntyExceptionFrame frame; \ frame.message[0] = 0; \ frame.next = (ntyExceptionFrame*)ntyThreadLocalDataGet(ExceptionStack); \ ntyThreadLocalDataSet(ExceptionStack, &frame); \ Exception_flag = setjmp(frame.env); \ if (Exception_flag == ExceptionEntered) {#define Catch(nty_exception) \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } else if (frame.exception == &(nty_exception)) { \ Exception_flag = ExceptionHandled;#define Finally \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } { \ if (Exception_flag == ExceptionEntered) \ Exception_flag = ExceptionFinalized;#define EndTry \ if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; \ } if (Exception_flag == ExceptionThrown) {ReThrow;} \ } while (0)void ntyExceptionThrow(ntyException *excep, const char *func, const char *file, int line, const char *cause, ...) { va_list ap; ntyExceptionFrame *frame = (ntyExceptionFrame *) ntyThreadLocalDataGet(ExceptionStack); if (frame) { //异常名 frame->exception = excep; frame->func = func; frame->file = file; frame->line = line; //异常打印的信息 if (cause) { va_start(ap, cause); vsnprintf(frame->message, EXCEPTION_MESSAGE_LENGTH, cause, ap); va_end(ap); } ntyExceptionPopStack; longjmp(frame->env, ExceptionThrown); } //没有被catch,直接throw else if (cause) { char message[EXCEPTION_MESSAGE_LENGTH + 1]; va_start(ap, cause); vsnprintf(message, EXCEPTION_MESSAGE_LENGTH, cause, ap); va_end(ap); printf("%s: %s
raised in %s at %s:%d
", excep->name, message, func ? func : "?", file ? file : "?", line); } else { printf("%s: %p
raised in %s at %s:%d
", excep->name, excep, func ? func : "?", file ? file : "?", line); }}/* ** **** ******** **************** debug **************** ******** **** ** */ntyException A = {"AException"};ntyException B = {"BException"};ntyException C = {"CException"};ntyException D = {"DException"};void *thread(void *args) { pthread_t selfid = pthread_self(); Try { Throw(A, "A"); } Catch (A) { printf("catch A : %ld
", selfid); } EndTry; Try { Throw(B, "B"); } Catch (B) { printf("catch B : %ld
", selfid); } EndTry; Try { Throw(C, "C"); } Catch (C) { printf("catch C : %ld
", selfid); } EndTry; Try { Throw(D, "D"); } Catch (D) { printf("catch D : %ld
", selfid); } EndTry; Try { Throw(A, "A Again"); Throw(B, "B Again"); Throw(C, "C Again"); Throw(D, "D Again"); } Catch (A) { printf("catch A again : %ld
", selfid); } Catch (B) { printf("catch B again : %ld
", selfid); } Catch (C) { printf("catch C again : %ld
", selfid); } Catch (D) { printf("catch B again : %ld
", selfid); } EndTry;}#define PTHREAD_NUM 8int main(void) { ntyExceptionInit(); printf("
=> Test1: Throw
"); { Throw(D, NULL); //ntyExceptionThrow(&(D), "_function_name_", "_file_name_", 202, ((void *) 0), ((void *) 0)) Throw(C, "null C"); //ntyExceptionThrow(&(C), "_function_name_", "_file_name_", 203, "null C", ((void *) 0)) } printf("=> Test1: Ok
"); printf("
=> Test2: Try-Catch Double Nesting
"); { Try { Try { Throw(B, "call B"); } Catch (B) { printf("catch B
"); } EndTry; Throw(A, NULL); } Catch(A) { printf("catch A
"); printf("Result: Ok
"); } EndTry; } printf("=> Test2: Ok
"); printf("
=> Test3: Try-Catch Triple Nesting
"); { Try { Try { Try { Throw(C, "call C"); } Catch (C) { printf("catch C
"); } EndTry; Throw(B, "call B"); } Catch (B) { printf("catch B
"); } EndTry; Throw(A, NULL); } Catch(A) { printf("catch A
"); } EndTry; } printf("=> Test3: Ok
"); printf("=> Test4: Test Thread-safeness
"); int i = 0; pthread_t th_id[PTHREAD_NUM]; for (i = 0; i < PTHREAD_NUM; i++) { pthread_create(&th_id[i], NULL, thread, NULL); } for (i = 0; i < PTHREAD_NUM; i++) { pthread_join(th_id[i], NULL); } printf("=> Test4: Ok
"); printf("
=> Test5: No Success Catch
"); { Try { Throw(A, "no catch A ,should Rethrow"); } EndTry; } printf("=> Test5: Rethrow Success
"); printf("
=> Test6: Normal Test
"); { Try { Throw(A, "call A"); } Catch(A) { printf("catch A
"); } Finally { printf("wxf nb
"); }; EndTry; } printf("=> Test6: ok
");}void all() { ///try do { volatile int Exception_flag; ntyExceptionFrame frame; frame.message[0] = 0; frame.next = (ntyExceptionFrame *) pthread_getspecific((ExceptionStack)); pthread_setspecific((ExceptionStack), (&frame)); Exception_flag = _setjmp(frame.env); if (Exception_flag == ExceptionEntered) { /// { ///try do { volatile int Exception_flag; ntyExceptionFrame frame; frame.message[0] = 0; frame.next = (ntyExceptionFrame *) pthread_getspecific((ExceptionStack)); pthread_setspecific((ExceptionStack), (&frame)); Exception_flag = _setjmp(frame.env); if (Exception_flag == ExceptionEntered) { /// { ///Throw(B, "recall B"); --->longjmp ExceptionThrown ntyExceptionThrow(&(B), "_function_name_", "_file_name_", 302, "recall B", ((void *) 0)); /// } ///Catch (B) if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; } else if (frame.exception == &(B)) { Exception_flag = ExceptionHandled; /// { /// printf("recall B
"); /// } fin if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; if (Exception_flag == ExceptionEntered) Exception_flag = ExceptionFinalized; /{ { printf("fin
"); }; } ///EndTry; if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; } if (Exception_flag == ExceptionThrown) ntyExceptionThrow(frame.exception, frame.func, frame.file, frame.line, ((void *) 0)); } while (0); ///Throw(A, NULL); longjmp ExceptionThrown ntyExceptionThrow(&(A), "_function_name_", "_file_name_", 329, ((void *) 0), ((void *) 0)); /// } ///Catch(A) if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; } else if (frame.exception == &(A)) { Exception_flag = ExceptionHandled; /// { /// printf(" Result: Ok
"); /// } /// EndTry; if (Exception_flag == ExceptionEntered) ntyExceptionPopStack; } if (Exception_flag == ExceptionThrown) ntyExceptionThrow(frame.exception, frame.func, frame.file, frame.line, ((void *) 0)); } while (0); ///} 原文地址：手把手教你纯c实现异常捕获try-catch组件
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