Is this the correct syntax for passing a file pointer by reference?
Function call: printNew(&fpt);
printNew(FILE **fpt)
{
//change to fpt in here kept after function exits?
}
Thanks.
views:
117answers:
2
+4
A:
No. The correct syntax is
void printNew(FILE *&fpt)
{
//change to fpt in here kept after function exits?
}
Your code will only change the local pointer to a FILE pointer. Only changes to *fpt are seen by the caller in your code. If you change it to the above, things are passed by reference and changes are promoted like intended. The corresponding argument is passed as usual
printNew(fpt);
Johannes Schaub - litb
2010-07-12 18:15:22
@Tommy Your acceptance of this (correct for c++) answer leaves us no clearer if the this question is actually about C++, or C.
anon
2010-07-12 18:51:38
@Tommy why have you accepted my answer, but retagged your question to C? That makes no sense to me.
Johannes Schaub - litb
2010-07-12 19:39:30
@Johannes: re-tag to C was a error, changed back to C++ as intended.
Tommy
2010-07-12 20:25:57
+2
A:
I'd be interested in what you are going to do with that file pointer - the normal things you do on an open pointer are to call functions like fgets() and close it with fclose(), none of which require a reference.
anon
2010-07-12 18:19:58
Close the file, and open a new one with that pointer. Reference not needed?
Tommy
2010-07-12 18:24:04
@Tommy If you need the newly opened file to be accessible after the function returns, then yes. But I think I might to make the function return the new pointer as its return value.
anon
2010-07-12 18:39:15
@Tommy I meant of course - "then yes, reference needed". But I'd still prefer a return value.
anon
2010-07-12 18:49:36