Re: On non-Windows, hard depend on uselocale(3)

Peter Eisentraut <peter(at)eisentraut(dot)org> writes:
> On 28.08.24 20:50, Peter Eisentraut wrote:
>> I suggest that the simplification of the xlocale.h configure tests could
>> be committed separately. This would also be useful independent of this,
>> and it's a sizeable chunk of this patch.

> To keep this moving along a bit, I have extracted this part and
> committed it separately. I had to make a few small tweaks, e.g., there
> was no check for xlocale.h in configure.ac, and the old
> xlocale.h-including stanza could be removed from chklocale.h. Let's see
> how this goes.

For the archives' sake --- I discovered today during a "git bisect"
session that commits between 35eeea623 ("Use thread-safe
nl_langinfo_l(), not nl_langinfo()") and 9c2a6c5a5 ("Simplify checking
for xlocale.h", the commit Peter refers to here) fail to build on
current macOS (26/Tahoe):

chklocale.c:330:8: error: call to undeclared function 'nl_langinfo_l'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
330 | sys = nl_langinfo_l(CODESET, loc);
| ^
chklocale.c:330:8: note: did you mean 'nl_langinfo'?
/Library/Developer/CommandLineTools/SDKs/MacOSX26.1.sdk/usr/include/_langinfo.h:116:20: note: 'nl_langinfo' declared here
116 | char *_LIBC_CSTR nl_langinfo(nl_item);
| ^
chklocale.c:330:6: error: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
330 | sys = nl_langinfo_l(CODESET, loc);
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

This happens because nl_langinfo_l() is declared in xlocale.h,
but chklocale.c elects not to #include that, evidently because
it's no longer needed to obtain typedef locale_t.

AFAICS there's nothing we can do about this retroactively;
it'll be a more or less permanent landmine for bisecting on macOS.
Fortunately it's not too difficult to work around, you can just do

diff --git a/src/port/chklocale.c b/src/port/chklocale.c
index 9506cd87ed8..0e35e0cf55f 100644
--- a/src/port/chklocale.c
+++ b/src/port/chklocale.c
@@ -23,9 +23,7 @@
#include <langinfo.h>
#endif

-#ifdef LOCALE_T_IN_XLOCALE
#include <xlocale.h>
-#endif

#include "mb/pg_wchar.h"

when trying to build one of the affected commits. Another option
that might fit into a bisecting workflow more easily is to inject
-DLOCALE_T_IN_XLOCALE into CPPFLAGS.

regards, tom lane