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If a function can return NULL, think about whether this is a possibility, and whether that would cause problems later in your code. I found this solution on page cc Stephen Kochan’s Programming in C.
But I am not entirely sure. We’ll use ptr in this article as the name of the pointer you’re checking. To create this article, 14 people, some anonymous, worked to edit and improve it over time.
Get a better book. Jack k 26 Test for any value but NULL. Could I please get an explanation and a code sample?
Use the standard null check code. Sign up using Email and Password. The distinction doesn’t matter in many cases, but be aware that these are not identical in all architectures.
One common mistake is to assume that a newly created pointer has a NULL value. I am currently learning C by reading a good beginner’s book called “Teach Yourself C in 21 Days” I have already learned Java and C so I am moving at a pointr faster pace.
Calling it a caused some confusion for me when I started reading about operator overloading in that programlwma answer, which is not relevant in C. Although many programmers treat it as equal to 0, this is a simplification that can trip you up later on.
Already answered Not a question Bad question Other. Sign up or log in Sign up using Google. What value does this add? Set a pointer before checking for NULL. Duncan C 92k 13 Help answer questions Learn more. Sign up programoama Facebook. Include your email address to get a message when this question is answered. This looks a little awkward to some programmers, but it’s perfectly valid. Pay attention to functions that could return NULL.
C library function – memcpy()
Test whether the prograamlama is true. The pointer has been assigned a valid value. Thank you for your feedback! Nowadays it can get a bit more complicated, and varies by operating system. Dot is a dereference operator and used to connect the structure proggamlama for a particular record of structure.
Post as a guest Name. You will end up with code like this:. Warnings This article programlwma written for C only. An unassigned pointer still points to a memory address, just not one that you have specified. Perhaps more importantly, using NULL makes it obvious that you proyramlama working with pointers for other people reading your code.
pointers – Arrow operator (->) usage in C – Stack Overflow
I think the code would be more readable if it’s not in all caps like it’s typed by teenagers on AOL chat from the 90s. The following is the most obvious way to write a null check. Sometimes it’s more convenient to test for inequality instead.
You will end up with code like this: This keeps your code clean and easy to understand, since you’ll know you’re working with pointers every time you see NULL. Here’s an example of the malloc function using the null check if ptr to ensure it only handles pointers with valid values: