sizeofdst

Sizeofdst is a term used in programming to refer to the size of a destination buffer used when performing copy operations. It is not a standard language feature but a convention in some codebases to describe the maximum number of bytes that can be written to a destination without overflowing. In practice, sizeofdst is often realized as a macro or helper that yields the size of a fixed-size array intended as the destination.

In C and C++, a common pattern defines a macro such as sizeofdst(x) that expands to the number of elements in an array x, typically implemented as sizeof(x) / sizeof((x)[0]). This approach works only when the destination is a true array with automatic storage duration or static storage duration. It does not work for pointers or dynamically allocated buffers.

The macro is typically used with safe copying functions that take the destination size as a parameter, such as strlcpy or memcpy wrappers, to help enforce bounds. For example, if dst is a char array declared as char dst[256], then size_t n = sizeofdst(dst); strlcpy(dst, src, n); This use helps prevent buffer overruns by making the destination capacity explicit at the call site.

Limitations include the potential for misusing sizeofdst on function parameters that decay into pointers, or on dynamically allocated memory where the size is not captured by the macro. In languages with more robust standard facilities, alternatives include std::size in C++ or using modern safe string handling APIs.

See also: buffer overflow, safe string handling, strlcpy, std::size, array size macro.