Why is `size_t` Unsigned Despite the Known Drawbacks?

Why is size_t Unsigned?

Question:

In his book, Bjarne Stroustrup advises against using unsigned integers to gain an additional bit for representing positive integers. However, size_t, a type commonly used for representing array and string sizes, is unsigned. Was this a mistake, and should usage of size_t be minimized?

Answer:

size_t is unsigned due to historical reasons:

Architectural Limitations:

On older architectures with 16-bit pointers, limiting strings to 32 KB would be impractical. To address this, the C standard requires ptrdiff_t, the signed counterpart to size_t, to have an effective range of 17 bits.

Embedded Systems:

In certain embedded programming environments, these historical reasons still hold true.

Disadvantages of Unsigned Types:

However, in modern 32-bit and 64-bit programming, unsigned types present significant disadvantages:

• Implicit Conversion Rules: C and C 's implicit conversion rules treat unsigned types as bug attractors, as they allow operations and comparisons that may produce unexpected results (e.g., string("Hi").length() < -3).

Conclusion:

The decision to make size_t unsigned was not a mistake considering the architectural limitations of the time. However, in modern programming practice, using unsigned types for numerical operations is strongly discouraged due to their inherent drawbacks.

The above is the detailed content of Why is `size_t` Unsigned Despite the Known Drawbacks?. For more information, please follow other related articles on the PHP Chinese website!