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petke
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 Posted: Tue Jul 25, 2006 5:25 am Post subject: howto catch nothing? |
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Hi
I was wondering what happens when you throw nothing. As in how does one
catch that. If you cant I wonder why compilers allow throws like this.
try {
throw;
} catch( ... ) { // what goes here?
;
}
/Petke
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red floyd
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| Posted: Tue Jul 25, 2006 6:22 am Post subject: Re: howto catch nothing? |
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petke wrote:
| Quote: | Hi
I was wondering what happens when you throw nothing. As in how does one
catch that. If you cant I wonder why compilers allow throws like this.
try {
throw;
} catch( ... ) { // what goes here?
;
}
/Petke
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It rethrows the current exception (15.1/6-7). If no exception is
currently being handled, terminate() is called (15.1/ .
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Bob Bell
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| Posted: Wed Jul 26, 2006 6:03 am Post subject: Re: howto catch nothing? |
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petke wrote:
| Quote: | I tried to catch a exeption by reference and
modify it, but it seems the exception gets thrown by value anyway. Am I
missing something, or maybe exceptions and references just dont mix?
int i = 0;
try {
int &ex = i;
ex++;
throw ex;
} catch(int &ex) { //i=1, ex=1
try {
ex++;
throw; //re-throw
} catch(int &ex) { //i=1, ex=2
ex++;//"catched re-trow"
} //i=1, ex=3
}
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When you "throw ex;" it makes a copy of the value you are throwing (if
I remember correctly, using the copy constructor). Thereafter, in the
catch blocks, "ex" is a reference to the copy, so you can modify it if
you wish.
The reason the copy is made is that the original object may not exist,
as in:
try {
int i;
int& ex(i);
throw ex;
}
catch (int& ex) {
// i no longer exists; ex must not refer to it.
}
Bob
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