run-time error
- the basic philosophy of c++ is that "badly formed code will not be run"
- there's always something happen in run-time
- it is very important to deal with all possible situation in the future running
read a file
- open the file
- determine its size
- allocate that much memory
- read the file into memory
- close the file
errorCode Type readeFile{
initialize errorCode = 0;
open the file;
if(theFileOpen){
determine its size;
if(gotTheFileLength){
allocate that much memory;
if(gotEnoughMemoty){
read the file into memory;
if(readFailed){
errorCode = -1;
}
}else{
errorCode = -2;
}
}else{
errorCode = -3;
}
close the file;
if(theFIEDidntClose&&errorCode ==0){
errorCode = -4;
}else{
errorCode = errorCode and -4;
}
}else{
errorCode = -5;
}
return errorCode;
}
working w/exception
try{
open the file;
determine its size;
allocate that much memory;
read the file into memory;
close the file;
}catch(fileOpenFailed){
doSomting;
}catch(sizeDeterminationFailed){
doSomting;
}catch(memoryAllocationFailed){
doSomting;
}catch(readFailed){
doSomting;
}catch(fileCloseFailed){
doSomting;
}
exception
- I take exception to that
- At the point where the problem occurs,you might not known what to do with it,but you do know that you can't just continue on merrily;you must stop ,and somebody,somewhere,must figure out what to do
why exception? 清晰
- the significant benefit of exceptions is that they clean up error handing code
- it separates the code that describes what you want to do from the code that is executed
