"auto" is only meaningful in functions which accept an encoding
*list* and support encoding detection. These functions have
explicit checks for "auto". It cannot be used as a standalone
encoding in any meaningful capacity, so I'm dropping it entirely.
The C89 standard and later defines the `<string.h>` header as part of
the standard headers [1] and on current systems it is always present.
Code included also `<strings.h>` header as an alterinative in some
files. This kind of check was relevant on some older systems where the
`<strings.h>` file included definitions for the C89 compliant
`<string.h>`. Today such alternative check is not required anymore. The
`<strings.h>` file is part of the POSIX definition these days.
Also Autoconf suggests doing this and relying on C89 or above [2] and [3].
This patch also cleans few unused `<strings.h>` inclusions in the libmbfl.
[1]: https://port70.net/~nsz/c/c89/c89-draft.html#4.1.2
[2]: http://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/headers.m4
[3]: https://www.gnu.org/software/autoconf/manual/autoconf-2.69/autoconf.html
The `<stddef.h>` header file is part of the standard C89 headers [1] and
on current systems there is no need for a manual check if header is
present.
Since PHP requires at least C89 the `HAVE_STDDEF_H` symbol isn't defined
by Autoconf anywhere else anymore [2] and accross the PHP source code
the header is included unconditionally already.
This patch syncs this also for the bundled libmbfl which is maintaned as
a fork in php-src.
Refs:
[1] https://port70.net/~nsz/c/c89/c89-draft.html#4.1.2
[2] https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/headers.m4
For functions like mb_chr() and mb_ord() just looking up the
input/output filter for the encoding dominates the runtime. This
commit stores the input/output filter for an encoding in the
mbfl encoding structure, so it can be looked up directly, rather
than scanning through filter function lists.
Nikita Popov