[PATCH] Fix build failure on macOS 26.2 SDK due to missing nl_langinfo_l declaration - Mailing list pgsql-hackers

Hi,

  Building PostgreSQL against the macOS 26.2 SDK (Xcode 26 beta) fails
  with the following error:

    src/port/chklocale.c:326:8: error: call to undeclared function
    'nl_langinfo_l'; ISO C99 and later do not support implicit function
    declarations [-Wimplicit-function-declaration]
        sys = nl_langinfo_l(CODESET, loc);

  == Root Cause ==

  macOS 26.2 SDK changed the structure of <langinfo.h>.  In previous
  SDK versions, nl_langinfo_l() was declared unconditionally.  In the
  new SDK, it is only exposed when _USE_EXTENDED_LOCALES_ is defined,
  guarded behind a conditional include of <xlocale/_langinfo.h>:

    /* macOS 26.2 SDK: langinfo.h */
    #include <_langinfo.h>          /* nl_langinfo() only */

    #ifdef _USE_EXTENDED_LOCALES_
    #include <xlocale/_langinfo.h>  /* nl_langinfo_l() */
    #endif

  PostgreSQL's chklocale.c only includes <langinfo.h> directly, so
  nl_langinfo_l() is no longer visible on macOS 26.2.

  == Fix ==

  Include <xlocale.h> explicitly on Apple platforms.  This header
  declares nl_langinfo_l() unconditionally and is the standard way
  to access locale-specific extensions on macOS.

  Tested on macOS 26.2 (darwin 25.3) with Apple Clang 17.

  Patch attached.

  Regards,
  Jianghua Yang