Thread: program error :counting length of string

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Originally Posted by dwks

What's wrong with mine?

Its not wrong. (I will begin eating crow very soon...)
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Well strchr returns NULL if it does not find the character you specified. So then, knowing that fgets will read in one less than size, it is quite possible that there will be no newline in the array. In that case you will get a NULL return from strchr, and in that case you will be dereferencing a NULL pointer, which is generally a Bad Thing.

edit::

You need the extra brackets with the != operator, otherwise you would have something like this:

Code:

if(p = (strchr(string_data, '\n') != NULL)) {

thereby assigning either zero or non-zero to p.

Well strchr returns NULL if it does not find the character you specified.

Precisely. NULL is false. It's like doing this:

Code:

if(something != 0)

versus this

Code:

if(something)

Originally Posted by kermit

edit::

You need the extra brackets with the != operator, otherwise you would have something like this:

Code:

if(p = (strchr(string_data, '\n') != NULL)) {

thereby assigning either zero or non-zero to p.

That's not what I meant at all. I was wondering if this is valid C:

Code:

if(x = function())

or if you need extra brackets:

Code:

if((x = function()))

I don't see why you would need them.

Let me break it down for you.

Code:

if((p = strchr(string_data, '\n'))!= NULL)
if((p = strchr(string_data, '\n')))
if(p = strchr(string_data, '\n'))

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Yes, your version is clearer. But my version isn't an error.
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