pointer and memory question

[Janice]

int* ptr;
int i;
fread(&i,sizeof(int),0L,fs);
fread(ptr,sizeof(int),0L,fs);

Which way of declaring the buffer for the fread is better?
Thanx

 

[Richard Heathfield]

int* ptr;
int i;
fread(&i,sizeof(int),0L,fs);
fread(ptr,sizeof(int),0L,fs);

Which way of declaring the buffer for the fread is better?

Well, the first one is more likely to work. You can fix the second one like
this:

ptr = &i;

I suggest:

fread(&i, sizeof i, 1, fs);

Please note that a 0 for the third argument isn't going to read very many
objects, no matter how often you do it.

 

[Alexei A. Frounze]

Well, the first one is more likely to work. You can fix the second one like
this:

ptr = &i;

I suggest:

fread(&i, sizeof i, 1, fs);

Please note that a 0 for the third argument isn't going to read very many
objects, no matter how often you do it.

I'd also note that the data stored in the file that you're reading with this
fread is not portable among different platforms.
That's for endianness and sizeof(int) reasons.

Alex

 

[Malcolm]

int* ptr;
int i;
fread(&i,sizeof(int),0L,fs);
fread(ptr,sizeof(int),0L,fs);

Which way of declaring the buffer for the fread is better?

ptr needs to point to some memory.

Generally you don't want to fread / fwrite a single int. It is not portable,
and almost always it is better to reconstruct the integer from a stream.

 

[David Lago]

int* ptr;
int i;
fread(&i,sizeof(int),0L,fs);
fread(ptr,sizeof(int),0L,fs);

Which way of declaring the buffer for the fread is better?
Thanx

First one doesn't actually declare any buffer space (it is only an
uninitialized pointer).

David.
--
David Lago <[email protected]>

PGP key available at: http://pgp.mit.edu
Personal Blizog: http://arcanelinux.org/blog/dlworld
The Enflame Project: http://enflame.org

 

[Cong Wang]

I'd also note that the data stored in the file that you're reading with this
fread is not portable among different platforms.
That's for endianness and sizeof(int) reasons.

Alex

I agree with Richard Heathfield.
Try POSIX function--read() instead.

 

[Richard Heathfield]

I agree with Richard Heathfield.
Try POSIX function--read() instead.

But I don't agree with you, I'm afraid. What he needs to do can almost
certainly be done with fread(), which has the advantage over read() that it
does not require a POSIX-conforming implementation.

 

[Emmanuel Delahaye]

David Lago wrote on 15/07/05 :

First one doesn't actually declare any buffer space (it is only an
uninitialized pointer).

You meant the second one, don't you ?

--
Emmanuel
The C-FAQ: http://www.eskimo.com/~scs/C-faq/faq.html
The C-library: http://www.dinkumware.com/refxc.html

I once asked an expert COBOL programmer, how to
declare local variables in COBOL, the reply was:
"what is a local variable?"