diff options
Diffstat (limited to 'lib/idx.h')
| -rw-r--r-- | lib/idx.h | 22 |
1 files changed, 21 insertions, 1 deletions
@@ -1,5 +1,5 @@ /* A type for indices and sizes. - Copyright (C) 2020-2021 Free Software Foundation, Inc. + Copyright (C) 2020-2023 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -56,6 +56,26 @@ * Because 'size_t' is an unsigned type, and a signed type is better. See above. + Why not use 'ssize_t'? + + * 'ptrdiff_t' is more portable; it is standardized by ISO C + whereas 'ssize_t' is standardized only by POSIX. + + * 'ssize_t' is not required to be as wide as 'size_t', and some + now-obsolete POSIX platforms had 'size_t' wider than 'ssize_t'. + + * Conversely, some now-obsolete platforms had 'ptrdiff_t' wider + than 'size_t', which can be a win and conforms to POSIX. + + Won't this cause a problem with objects larger than PTRDIFF_MAX? + + * Typical modern or large platforms do not allocate such objects, + so this is not much of a problem in practice; for example, you + can safely write 'idx_t len = strlen (s);'. To port to older + small platforms where allocations larger than PTRDIFF_MAX could + in theory be a problem, you can use Gnulib's ialloc module, or + functions like ximalloc in Gnulib's xalloc module. + Why not use 'ptrdiff_t' directly? * Maintainability: When reading and modifying code, it helps to know that |