Good time of day. This commit breaks compilation at least on GCC 4.8.3: commit e5b2ee634c7151484c06740ea2c8a4d4a75409b6 Author: Paul Eggert <eggert@cs.ucla.edu> Date: Thu Oct 20 11:41:27 2022 -0700 Use C23 __has_include if available It causes this compilation error: zic.c: In function ‘main’: zic.c:813:16: error: ‘optarg’ undeclared (first use in this function) if (strcmp(optarg, "slim") == 0) { ^ zic.c:906:6: error: ‘optind’ undeclared (first use in this function) if (optind == argc - 1 && strcmp(argv[optind], "=") == 0) ^ Specifically hunks like this are problematic: @@ -55,8 +63,8 @@ #endif #ifndef HAVE_GETTEXT -# define HAVE_GETTEXT 0 -#endif /* !defined HAVE_GETTEXT */ +# define HAVE_GETTEXT HAS_INCLUDE(<libintl.h>, false) +#endif #ifndef HAVE_INCOMPATIBLE_CTIME_R # define HAVE_INCOMPATIBLE_CTIME_R 0 The culprit is the replacement 0 -> false and 1 -> true. Apparently it breaks #if preprocessor logic in older compilers somewhere downstream - what was #if 1 becomes #if true, which GCC treats as "false" and falls into #else branch. "Restoring" false and true back to 0 and 1 seems to fix the issue. Best regards, Igor Ivanov, Software engineer at DSSL