int func(){ int bIsErrOccur = 0; //do something that might invoke errors if(bIsErrOccur) //Stage 1: error occurred return -1; //Stage 2: generate error indicator //... return 0;}
int main(void){ if(func() != 0) //Stage 3: detect error { //Stage 4: handle error } //Stage 5: recover or abort return 0;}

if((p = malloc(100)) == NULL) //...
if((c = getchar()) == EOF) //...
if((ticks = clock()) < 0) //...

char *IntToAscii(int dwVal, char *pszRes, int dwRadix){ if(NULL == pszRes) return "Arg2Null";
 if((dwRadix < 2) || (dwRadix > 36)) return "Arg3OutOfRange";
 //... return pszRes;}

typedef enum{ S_OK, //成功 S_ERROR, //失败(原因未明确)，通用状态 S_NULL_POINTER, //入参指针为NULL S_ILLEGAL_PARAM, //参数值非法，通用 S_OUT_OF_RANGE, //参数值越限 S_MAX_STATUS //不可作为返回值状态，仅作枚举最值使用}FUNC_STATUS;
#define RC_NAME(eRetCode) \ ((eRetCode) == S_OK ? "Success" : \ ((eRetCode) == S_ERROR ? "Failure" : \ ((eRetCode) == S_NULL_POINTER ? "NullPointer" : \ ((eRetCode) == S_ILLEGAL_PARAM ? "IllegalParas" : \ ((eRetCode) == S_OUT_OF_RANGE ? "OutOfRange" : \ "Unknown")))))

extern int errno;

extern int *__errno_location(void);#define errno (*__errno_location())

//调用库函数if(返回错误值) //检查errno

if (somecall() == -1){ int dwErrSaved = errno; printf("somecall() failed\n"); if(dwErrSaved == ...) { ... }}

#include <stdio.h>void perror(const char *msg);

int main(int argc, char** argv){ errno = 0; FILE *pFile = fopen(argv[1], "r"); if(NULL == pFile) { printf("Cannot open file '%s'(%s)!\n", argv[1], strerror(errno)); perror("Open file failed"); } else { printf("Open file '%s'(%s)!\n", argv[1], strerror(errno)); perror("Open file"); fclose(pFile); }
 return 0;}

[wangxiaoyuan_@localhost test1]$ ./GlbErr /sdb1/wangxiaoyuan/linux_test/test1/test.cOpen file '/sdb1/wangxiaoyuan/linux_test/test1/test.c'(Success)!Open file: Success[wangxiaoyuan_@localhost test1]$ ./GlbErr NonexistentFile.hCannot open file 'NonexistentFile.h'(No such file or directory)!Open file failed: No such file or directory[wangxiaoyuan_@localhost test1]$ ./GlbErr NonexistentFile.h > testOpen file failed: No such file or directory[wangxiaoyuan_@localhost test1]$ ./GlbErr NonexistentFile.h 2> testCannot open file 'NonexistentFile.h'(No such file or directory)!

int *_fpErrNo(void){ static int dwLocalErrNo = 0; return &dwLocalErrNo;}
#define ErrNo (*_fpErrNo())#define EOUTOFRANGE 1//define other error macros...
int Callee(void){ ErrNo = 1; return -1;}
int main(void){ ErrNo = 0; if((-1 == Callee()) && (EOUTOFRANGE == ErrNo)) printf("Callee failed(ErrNo:%d)!\n", ErrNo); return 0;}

double Division(double fDividend, double fDivisor){ return fDividend/fDivisor;}int main(void){ int dwFlag = 0; if(1 == dwFlag) { RaiseException: printf("The divisor cannot be 0!\n"); exit(1); } dwFlag = 1;
 double fDividend = 0.0, fDivisor = 0.0; printf("Enter the dividend: "); scanf("%lf", &fDividend); printf("Enter the divisor : "); scanf("%lf", &fDivisor); if(0 == fDivisor) //不太严谨的浮点数判0比较 goto RaiseException; printf("The quotient is %.2lf\n", Division(fDividend, fDivisor));
 return 0;}

[wangxiaoyuan_@localhost test1]$ ./testEnter the dividend: 10Enter the divisor : 0The divisor cannot be 0![wangxiaoyuan_@localhost test1]$ ./testEnter the dividend: 10Enter the divisor : 2The quotient is 5.00虽然goto语句会破坏代码结构性，但却非常适用于集中错误处理。伪代码示例如下：CallerFunc(){ if((ret = CalleeFunc1()) < 0); goto ErrHandle; if((ret = CalleeFunc2()) < 0); goto ErrHandle; if((ret = CalleeFunc3()) < 0); goto ErrHandle; //...
 return;
ErrHandle: //Handle Error(e.g. printf) return;}

#include <setjmp.h>int setjmp(jmp_buf env);void longjmp(jmp_buf env,int val);

jmp_buf gJmpBuf;void Func1(){ printf("Enter Func1\n"); if(0)longjmp(gJmpBuf, 1);}void Func2(){ printf("Enter Func2\n"); if(0)longjmp(gJmpBuf, 2);}void Func3(){ printf("Enter Func3\n"); if(1)longjmp(gJmpBuf, 3);}
int main(void){ int dwJmpRet = setjmp(gJmpBuf); printf("dwJmpRet = %d\n", dwJmpRet); if(0 == dwJmpRet) { Func1(); Func2(); Func3(); } else { switch(dwJmpRet) { case 1: printf("Jump back from Func1\n"); break; case 2: printf("Jump back from Func2\n"); break; case 3: printf("Jump back from Func3\n"); break; default: printf("Unknown Func!\n"); break; } } return 0;}

dwJmpRet = 0Enter Func1Enter Func2Enter Func3dwJmpRet = 3Jump back from Func3

jmp_buf gJmpBuf;void RaiseException(void){ printf("Exception is raised: "); longjmp(gJmpBuf, 1); //throw，跳转至异常处理代码 printf("This line should never get printed!\n");}double Division(double fDividend, double fDivisor){ return fDividend/fDivisor;}int main(void){ double fDividend = 0.0, fDivisor = 0.0; printf("Enter the dividend: "); scanf("%lf", &fDividend); printf("Enter the divisor : "); if(0 == setjmp(gJmpBuf)) //try块 { scanf("%lf", &fDivisor); if(0 == fDivisor) //也可将该判断及RaiseException置于Division内 RaiseException(); printf("The quotient is %.2lf\n", Division(fDividend, fDivisor)); } else //catch块(异常处理代码) { printf("The divisor cannot be 0!\n"); }
 return 0;}

Enter the dividend: 10Enter the divisor : 0Exception is raised: The divisor cannot be 0!

#include <signal.h>typedef void (*fpSigFunc)(int);fpSigFunc signal(int signo, fpSigFunc fpHandler);int raise(int signo);

void fphandler(int dwSigNo){ printf("Exception is raised, dwSigNo=%d!\n", dwSigNo);}int main(void){ if(SIG_ERR == signal(SIGFPE, fphandler)) { fprintf(stderr, "Fail to set SIGFPE handler!\n"); exit(EXIT_FAILURE); }
 double fDividend = 10.0, fDivisor = 0.0; if(0 == fDivisor) { raise(SIGFPE); exit(EXIT_FAILURE); } printf("The quotient is %.2lf\n", fDividend/fDivisor);
 return 0;}

int main(void){ if(SIG_ERR == signal(SIGFPE, fphandler)) { fprintf(stderr, "Fail to set SIGFPE handler!\n"); exit(EXIT_FAILURE); }
 int dwDividend = 10, dwDivisor = 0; double fQuotient = dwDividend/dwDivisor; printf("The quotient is %.2lf\n", fQuotient);
 return 0;}

#include <stdlib.h>void exit(int status);void _Exit(int status);#include <unistd.h>void _exit(int status);

int main(void){ printf("Using exit...\n"); printf("This is the content in buffer"); exit(0); printf("This line will never be reached\n");}

Using exit...This is the content in buffer(结尾无换行符)

int main(void){ printf("Using _exit...\n"); printf("This is the content in buffer"); fprintf(stdout, "Standard output stream"); fprintf(stderr, "Standard error stream"); //fflush(stdout); _exit(0);}

Using _exit...Standard error stream(结尾无换行符)

Using _exit...Standard error streamThis is the content in bufferStandard output stream(结尾无换行符)

#include <stdlib.h>int atexit(void (*func)(void));

double Division(double fDividend, double fDivisor){ return fDividend/fDivisor;}void RaiseException1(void){ printf("Exception is raised: \n");}void RaiseException2(void){ printf("The divisor cannot be 0!\n");}
int main(void){ double fDividend = 0.0, fDivisor = 0.0; printf("Enter the dividend: "); scanf("%lf", &fDividend); printf("Enter the divisor : "); scanf("%lf", &fDivisor); if(0 == fDivisor) { atexit(RaiseException2); atexit(RaiseException1); exit(EXIT_FAILURE); } printf("The quotient is %.2lf\n", Division(fDividend, fDivisor));
 return 0;}

Enter the dividend: 10Enter the divisor : 0Exception is raised: The divisor cannot be 0!

#include <stdlib.h>void abort(void);

void abort(void){ raise(SIGABRT); exit(EXIT_FAILURE);}

#ifdef NDEBUG #define assert(expr) ((void) 0)#else extern void __assert((const char *, const char *, int, const char *)); #define assert(expr) \ ((void) ((expr) || \ (__assert(#expr, __FILE__, __LINE__, __FUNCTION__), 0)))#endif

void __assert(const char *assertion, const char * filename, int linenumber, register const char * function){ fprintf(stderr, " [%s(%d)%s] Assertion '%s' failed.\n", filename, linenumber, ((function == NULL) ? "UnknownFunc" : function), assertion); abort();}

#undef assert#ifdef NDEBUG #define assert(expr) ((void) 0)#else #define assert(expr) ((void) ((expr) || \ (fprintf(stderr, "[%s(%d)] Assertion '%s' failed.\n", \ __FILE__, __LINE__, #expr), abort(), 0)))#endif

int main(void){ int dwChg = 0; assert(dwChg = 1); if(0 == dwChg) printf("Assertion should be enabled!\n"); return 0;}

#include <stdarg.h>#include <syslog.h>#define HAVE_VSNPRINTF 1#define MAXLINE 4096 /* max text line length */int daemon_proc; /* set nonzero by daemon_init() */static void err_doit(int errnoflag, int level, const char * fmt, va_list ap){ int errno_save, n; char buf[MAXLINE + 1];
 errno_save = errno; /* Value caller might want printed. */#ifdef HAVE_VSNPRINTF vsnprintf(buf, MAXLINE, fmt, ap);#else vsprintf(buf, fmt, ap); /* This is not safe */#endif n = strlen(buf); if (errnoflag) { snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save)); } strcat(buf, "\n");
 if (daemon_proc) { syslog(level, buf); } else { fflush(stdout); /* In case stdout and stderr are the same */ fputs(buf, stderr); fflush(stderr); }
 return;}
void err_ret(const char * fmt, ...){ va_list ap;
 va_start(ap, fmt); err_doit(1, LOG_INFO, fmt, ap); va_end(ap);
 return;}