Simplifying C Function Calls with Pointers and the Comma Operator

Discover how to efficiently call C functions using pointers without declaring extra variables, leveraging the power of the comma operator.
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This video is based on the question https://stackoverflow.com/q/68572283/ asked by the user 'PLB' ( https://stackoverflow.com/u/12391318/ ) and on the answer https://stackoverflow.com/a/68572653/ provided by the user 'Serge Ballesta' ( https://stackoverflow.com/u/3545273/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Simplifying C Function Calls with Pointers and the Comma Operator

When working with functions in C, you may encounter situations where you want to pass a pointer to a variable, but you don't want to declare that variable explicitly in your code. For instance, you might have a function prototype like this:

[[See Video to Reveal this Text or Code Snippet]]

The function writeData needs a pointer to a uint16_t variable. In typical usage, you would declare a variable, assign it a value, and then pass its address to the function, like this:

[[See Video to Reveal this Text or Code Snippet]]

However, if you want to avoid declaring dataValue, is there a way to call writeData directly with the value? Let’s explore our options.

Using the Comma Operator

One interesting solution to this problem is the use of the comma operator in C. This operator allows you to evaluate multiple expressions in a single statement, returning the value of the last expression. This means you can both assign a value to a variable and get its address within the same line. Here's how you can do it:

[[See Video to Reveal this Text or Code Snippet]]

Explanation

Expression Breakdown: In the above code:

The assignment dataValue = 55 is evaluated first, setting dataValue to 55.

Then, the address of dataValue is retrieved using &dataValue.

The entire expression (dataValue = 55, &dataValue) results in the address of dataValue.

Benefits: This approach eliminates the need for multiple lines of code just to handle a simple assignment and pointer addressing in a single function call.

Conclusion

In C programming, it's indeed possible to simplify how you interface with functions that require pointers. The comma operator enables you to both set a value and get the corresponding address. This not only reduces the number of lines needed but also maintains the clarity of your intentions in the code.

By understanding and using operators effectively, you can write cleaner and more efficient code that serves your programming objectives without unnecessary clutter. Now, next time you're faced with a similar issue, consider leveraging the comma operator for a streamlined solution!