uchar: Make #include_next work right

[Bruno Haible]

A coreutils prerelease fails to compile on AIX 7.1:

xlc -q64 -qthreaded -qtls  -I. -I.. -I./lib  -Ilib -I../lib -Isrc -I../src 
-I/home/haible/prefix64/include -D_THREAD_SAFE    -g -c -o 
lib/libcoreutils_a-btoc32.o `test -f 'lib/btoc32.c' || echo '../'`lib/btoc32.c
"./lib/uchar.h", line 913.44: 1506-275 (S) Unexpected text wc encountered.
"./lib/uchar.h", line 913.19: 1506-282 (S) The type of the parameters must be 
specified in a prototype.
"./lib/uchar.h", line 1070.29: 1506-277 (S) Syntax error: possible missing ')' 
or ','?
"./lib/uchar.h", line 1069.19: 1506-282 (S) The type of the parameters must be 
specified in a prototype.
"./lib/uchar.h", line 1155.29: 1506-277 (S) Syntax error: possible missing ')' 
or ','?
"./lib/uchar.h", line 1154.19: 1506-282 (S) The type of the parameters must be 
specified in a prototype.

This syntax errors occur because 'char32_t' is not defined, although
on this platform /usr/include/uchar.h ought to have defined it.

Deeper analysis shows that the '#include_next <uchar.h>' statement in
the generated lib/uchar.h does not work right, when the lib directory
occurs in more than one -I option:

$ xlc -q64 -qthreaded -qtls -I./lib  -Ilib   -g  foo.c -E | grep uchar.h
#line 6 "./lib/uchar.h"
$ xlc -q64 -qthreaded -qtls -I./lib   -g  foo.c -E | grep uchar.h
#line 29 "/usr/include/uchar.h"
#line 6 "./lib/uchar.h"
$ xlc -q64 -qthreaded -qtls -Ilib   -g  foo.c -E | grep uchar.h
#line 29 "/usr/include/uchar.h"
#line 6 "lib/uchar.h"

The cause is that gnulib's uchar.h does not have a split double-inclusion
guard, like it needs to have since it uses #include_next.

This patch fixes it. The other three patches are just for code consistency.


2023-08-26  Bruno Haible  <bruno@clisp.org>

        selinux-h: Add a comment.
        * lib/se-selinux.in.h: Clarify which #endif belongs to the
        double-inclusion guard.

2023-08-26  Bruno Haible  <bruno@clisp.org>

        sys_utsname: Make double-inclusion guard more robust.
        * lib/sys_utsname.in.h: Test the guard symbol a second time.

2023-08-26  Bruno Haible  <bruno@clisp.org>

        sys_times: Make double-inclusion guard more robust.
        * lib/sys_times.in.h: Test the guard symbol a second time.

2023-08-26  Bruno Haible  <bruno@clisp.org>

        uchar: Make #include_next work right.
        * lib/uchar.in.h: Use a split double-inclusion guard.

0001-uchar-Make-include_next-work-right.patch
Description: Text Data

0002-sys_times-Make-double-inclusion-guard-more-robust.patch
Description: Text Data

0003-sys_utsname-Make-double-inclusion-guard-more-robust.patch
Description: Text Data

0004-selinux-h-Add-a-comment.patch
Description: Text Data