Simmulating "exceptions" in pure C

 #include <stdio.h>  
 #include <setjmp.h>  
 typedef struct ExcHandlerDesc_ {  
     struct ExcHandlerDesc_ * prev;  
     jmp_buf jmpBuf;  
     int handled; // 0 = did not handle the exception  
     int excId; // the id of unhandled exception for rethrow  
 } ExcHandlerDesc;  
 static ExcHandlerDesc * xroot;  
 #define XR_CODE_BLOCK 0  
 #define XR_FINALLY_BLOCK -1  
 // starting exception id  
 #define XR_EXC_ID 2  
 //#define X_TRY(exchd_) addXHandler(exchd_); switch (setjmp(exchd_.jmpBuf)) {  
 //#define X_END(exchd_) }; removeXHandler(exchd_);  
 ////////  
 void throwIt(int v) {  
     if (xroot == 0) {  
         printf("Unhandled exception %i !!!\n", v);  
         exit(1);  
     }  
     xroot->excId = v;  
     //xroot->handled = 1;  
     longjmp(xroot->jmpBuf, v);  
 }  
 void addXHandler(ExcHandlerDesc*d) {  
     d->handled = 1;  
     d->prev = xroot;  
     xroot = d;  
 }  
 void removeXHandler() {  
     if (xroot) {  
         xroot = xroot->prev;      
     }  
 }  
 ////////  
 void funcWithExc() {  
     // throw  
     throwIt(2);  
 }  
 void func1() {  
     funcWithExc();  
 }  
 void func0()   
 {  
     int a;  
     // try  
     ExcHandlerDesc xhd;  
     addXHandler(&xhd);  
     a = setjmp(xhd.jmpBuf);  
     if ((a != XR_CODE_BLOCK) && (xroot == &xhd)) {  
         removeXHandler();  
     }  
     switch(a) {  
         case XR_CODE_BLOCK:  
             func1();  
             break;  
         case XR_FINALLY_BLOCK:  
             // do cleanup  
             if (!xhd.handled)  
                 throwIt(xhd.excId);  
             break;  
         case XR_EXC_ID:  
             // handle it  
             printf("Caught %i !\n", xhd.excId);  
             // handler is removed and rethrow here is allowed  
             throwIt(2);  
             break;  
         default:  
             // unhandled!  
             xhd.handled = 0;  
             break;  
     }  
     // cleanup  
     if (a != XR_FINALLY_BLOCK)  
         longjmp(xhd.jmpBuf, XR_FINALLY_BLOCK);  
     /// end exception handling  
 }  
 int main() {  
     func0();  
     return 0;  
 }