SSIZEMIN

SSIZEMIN is a symbolic constant used in some programming environments to denote the minimum value representable by the signed size type, typically ssize_t. It is not part of the C standard; the standard macro for the minimum ssize_t value is SSIZE_MIN, defined in many implementations’ limits.h, with SSIZE_MAX representing the maximum value.

In practice, SSIZEMIN (when it appears) is often an alias or alias-like stand-in for the minimum value of ssize_t. The exact numeric value depends on the architecture and the implementation. The minimum is generally the negation of the maximum plus one, i.e., -SSIZE_MAX-1, and on common architectures this yields values such as -9223372036854775808 on 64-bit systems and -2147483648 on 32-bit systems. Because SSIZEMIN is not standardized, portable code should prefer SSIZE_MIN if available or compute bounds from SSIZE_MAX.

SSIZE_MAX and its related macros come from the signed size type ssize_t, which is used for functions that can fail with negative error codes and to represent sizes for buffer lengths and indices. When code uses a minimum bound constant, SSIZEMIN (or SSIZE_MIN) helps to express sentinel values, underflow checks, and range validations in a way that mirrors the corresponding maximum bound.

Portability considerations are important: rely on the standard SSIZE_MIN macro where possible, or provide architecture-aware definitions if your environment defines SSIZEMIN as a non-standard alias. Documentation and comments should clarify the origin and intent of the constant to avoid misinterpretation across platforms.

See also: ssize_t, SSIZE_MIN, SSIZE_MAX, limits.h.