Why Do Array Lengths in C and C Function Signatures Seem to Be Ignored?

Array Lengths in Function Signatures: A Syntactical Curiosity

Despite the apparent presence of array lengths in function signatures in C and C , these lengths are effectively disregarded. This behavior has bewildered developers and raises questions about its purpose.

The Illusion of Array Length Control

Consider the following C code snippet:

#include <stdio.h>

int dis(char a[1]) {
    return strlen(a);
}

int main() {
    char b[4] = "abc";
    int c = dis(b);
    printf("%d\n", c);
    return 0;
}

In this code, the dis function expects an array of characters with a length of 1 ([1]). However, the user passes an array with a length of 4 (b). Surprisingly, the code compiles and executes without raising any errors. This suggests that the array length specified in the function signature is not enforced.

The True Nature of Array Passages

In C and C , arrays are not passed by value. Instead, a pointer to the first element of the array is passed. Therefore, the specification of an array length in a function signature becomes redundant, as this information can be derived from the pointer.

The Historical Rationale

The decision to allow array length specifications in function signatures was made in the early days of C, likely due to the legacy of earlier languages. Although this syntax has been maintained for compatibility reasons, it has become a source of confusion for developers.

Conclusion

The presence of array lengths in C and C function signatures is a syntactic quirk that does not actually enforce array lengths. This behavior is due to the underlying passing mechanism, which involves pointers to array elements rather than the arrays themselves. While this syntax may seem unnecessary, its historical origins have cemented its place in modern C and C programming languages.

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