openssl/NOTES-POSIX.md
Richard Levitte 4e8c4b77ef Add installation documentation and notes on ANSI C and POSIX
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24173)
2024-05-22 09:59:32 +02:00

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Notes on POSIX
==============
There are few instances where OpenSSL requires a POSIX C library, at least
version 1-2008, or compatible enough functionality.
There are exceptions, though, for platforms that do not have a POSIX
library, or where there are quirks that need working around. A notable
platform is Windows, where POSIX functionality may be available, but where
the function names are prefixed with an underscore, and where some POSIX
types are not present (such as `ssize_t`).
Platforms that do have a POSIX library may still not have them accessible
unless the following macros are defined:
_POSIX_C_SOURCE=200809L
_XOPEN_SOURCE=1
This is, for example, the case when building with gcc or clang and using the
flag `-ansi`.