Can C `new int[0]` Allocate Empty Memory, and If So, What Are the Implications?

Curiosity Corner: Allocating Empty Memory in C

In the realm of C programming, an intriguing question arises: Can we allocate memory for an empty block, represented by new int[0].

Observations from a Test Application

A simple test application that prints the result of new int[0] reveals an output of 0x876c0b8, suggesting that memory is indeed being allocated.

Diving into the Standard

The C Standard provides guidance on this matter:

• Zero-Sized Arrays: 5.3.4/7 states that a direct-new-declarator with an expression value of zero results in an allocation for an array with no elements.
• Undefined Dereferencing: 3.7.3.1/2 warns that dereferencing a pointer returned for a zero-size request has undefined behavior.

Additional Considerations

• Even with a zero-size request, the allocation may fail.
• While allocation is permitted, dereferencing the returned memory is not legally well-defined across platforms.
• You should delete the allocated memory, even if it has zero size.

Foot-Note Insights

An interesting foot-note from 3.7.3.1/2 reveals that the intention is to enable operator new() implementation using either malloc() or calloc(), which behave similarly with regards to zero-size requests. However, C differs from C by requiring a zero-size request to return a non-null pointer.

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