Why Doesn't C Guarantee Compile-Time Errors for Functions Missing Return Values?

Function with Non-void Return Type Returning Garbage

In C , if a function declares a non-void return type but fails to return a value, the compiler typically returns a garbage value. This raises the question: why isn't this considered an error at compile time?

Comparison to Uninitialized Variables

The analogy to uninitialized variables is not applicable. In case of an uninitialized variable, the compiler can detect the error statically because the allocation is local to the current function's stack frame. In contrast, function return values are allocated on the stack frame of the caller, making it more challenging for the compiler to track.

Undefined Behavior

According to the C standard, flowing off the end of a value-returning function results in undefined behavior. This means that the compiler is not obligated to detect or handle this situation.

Compiler Warnings

Most compilers issue warnings for code like the example provided:

int func2() {
    // does not return anything
}

These warnings indicate that the code is potentially unsafe and may lead to unexpected results.

Difficulty in Determining Function Exit

The C standard does not require compile-time error checking for this behavior because it can be challenging to determine whether the function indeed exits at the end or if it exits through an exception or some other control flow mechanism.

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