What is the Order of Parameter Evaluation in C and C Function Calls?

Order of Parameter Evaluation in Function Calls

In programming languages like C and C , the order in which function parameters are evaluated is a topic of debate. This article delves into the specifics outlined by the respective language standards.

C Language

According to the C99 and C11 standards, there is no fixed order for evaluating function parameters. The evaluation of the function designator, arguments, and sub-expressions within them occurs in an unspecified order, but there's a sequence point before the actual function call. This implies that side effects from parameter evaluations take place before the function enters its body.

C Language

In C , the language standard specifies that the order of argument evaluation in function calls is unspecified. All side effects of argument expression evaluations occur before the function is entered. The evaluation order of the postfix expression and the argument expression list is also unspecified.

Use of the Hardware Stack

Neither the C nor C standards require the use of the hardware stack to pass function parameters. The method of parameter passing is an implementation detail left to the compiler designer. While most architectures employ a stack-based approach, it isn't universally implemented.

Conclusion

The evaluation order of function parameters in C and C can vary depending on the implementation, as it's not explicitly defined by their language standards. However, it's crucial to note that side effects from argument evaluations take place before the respective functions are executed in both languages.

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