Add -Accflags=-DLIBC_HANDLES_MISMATCHED_CTYPE

Consider the name of a month in some language, Chinese for example.  If
LC_TIME has been set to a Chinese locale, strftime() can be used to
generate the Chinese month name for any given date, by using the
%B format.  But also suppose that LC_CTYPE is set to, say, "C".
The return from strftime() on many platforms will be mojibake given that
no Chinese month name is composed of just ASCII characters.  Perl
handles this for you by automatically toggling LC_CTYPE to whatever
LC_TIME is during the execution of strftime(), and afterwards restoring
it to its prior value.  But the strftime() (and similar functions) in
some libc implementations already do this toggle, meaning perl's action
is redundant.

This commit adds the ability for you to tell perl that a libc does this
(by setting this Configure option) and it will skip its syncing LC_CTYPE
and whatever the other locale is.

I propose to turn this on for all platforms as a smoke-me experiment,
and see which ones still yield proper results, and for those, add this
Configuration option to their hints files.

This commit doesn't change perl from syncing LC_CTYPE and LC_COLLATE
for operations related to collation.  It would require more work, and
I'd want to see the results of the experiment first.

diff --git a/locale.c b/locale.c
index 04c0377..6734d9e 100644 (file)
--- a/locale.c
+++ b/locale.c
@@ -282,6 +282,23 @@
  *          to be stripped off.  khw believes there aren't any such platforms
  *          still in existence.
  *
+ *      -Accflags=-DLIBC_HANDLES_MISMATCHED_CTYPE
+ *          Consider the name of a month in some language, Chinese for example.
+ *          If LC_TIME has been set to a Chinese locale, strftime() can be used
+ *          to generate the Chinese month name for any given date, by using the
+ *          %B format.  But also suppose that LC_CTYPE is set to, say, "C".
+ *          The return from strftime() on many platforms will be mojibake given
+ *          that no Chinese month name is composed of just ASCII characters.
+ *          Perl handles this for you by automatically toggling LC_CTYPE to
+ *          whatever LC_TIME is during the execution of strftime(), and
+ *          afterwards restoring it to its prior value.  But the strftime()
+ *          (and similar functions) in some libc implementations already do
+ *          this toggle, meaning perl's action is redundant.  You can tell perl
+ *          that a libc does this by setting this Configure option, and it will
+ *          skip its syncing LC_CTYPE and whatever the other locale is.
+ *          Currently, perl ignores this Configuration option and  syncs anyway
+ *          for LC_COLLATE-related operations, due to perl's internal needs.
+ *
  *      -Accflags=USE_FAKE_LC_ALL_POSITIONAL_NOTATION
  *          This is used when developing Perl on a platform that uses
  *          'name=value;' notation to represent LC_ALL when not all categories
@@ -367,6 +384,13 @@ static int debug_initialization = 0;
 #define PERL_IN_LOCALE_C
 #include "perl.h"
 
+/* Some platforms require LC_CTYPE to be congruent with the category we are
+ * looking for.  XXX This still presumes that we have to match COLLATE and
+ * CTYPE even on platforms that apparently handle this. */
+#if defined(USE_LOCALE_CTYPE) && ! defined(LIBC_HANDLES_MISMATCHED_CTYPE)
+#  define WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
+#endif
+
 #if PERL_VERSION_GT(5,39,9)
 #  error Revert the commit that added this line
 #endif
@@ -5438,10 +5462,8 @@ S_populate_hash_from_localeconv(pTHX_ HV * hv,
      * global static buffer.  Some locks might be no-ops on this platform, but
      * not others.  We need to lock if any one isn't a no-op. */
 
-#    ifdef USE_LOCALE_CTYPE
+#    ifdef WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
 
-    /* Some platforms require LC_CTYPE to be congruent with the category we are
-     * looking for */
     const char * orig_CTYPE_locale = toggle_locale_c(LC_CTYPE, locale);
 
 #    endif
@@ -5616,7 +5638,7 @@ S_populate_hash_from_localeconv(pTHX_ HV * hv,
     }
 
 #    endif
-#    ifdef USE_LOCALE_CTYPE
+#    ifdef WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
 
     restore_toggled_locale_c(LC_CTYPE, orig_CTYPE_locale);
 
@@ -6014,7 +6036,7 @@ S_my_langinfo_i(pTHX_
 
 /*--------------------------------------------------------------------------*/
 #  if defined(HAS_NL_LANGINFO) /* nl_langinfo() is available.  */
-#    ifdef USE_LOCALE_CTYPE
+#    ifdef WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
 
     /* This function sorts out if things actually have to be switched or not,
      * for both save and restore. */
@@ -6036,7 +6058,7 @@ S_my_langinfo_i(pTHX_
 
     restore_toggled_locale_i(cat_index, orig_switched_locale);
 
-#    ifdef USE_LOCALE_CTYPE
+#    ifdef WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
 
     restore_toggled_locale_c(LC_CTYPE, orig_CTYPE_locale);
 
@@ -6058,7 +6080,7 @@ S_my_langinfo_i(pTHX_
      * GetThreadLocale() doesn't work, as the former doesn't change the
      * latter's return.  Therefore we are stuck using the mechanisms below. */
 
-#    ifdef USE_LOCALE_CTYPE
+#    ifdef WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
 
     const char * orig_CTYPE_locale = toggle_locale_c(LC_CTYPE, locale);
 
@@ -6774,7 +6796,7 @@ S_my_langinfo_i(pTHX_
 
     restore_toggled_locale_i(cat_index, orig_switched_locale);
 
-#    ifdef USE_LOCALE_CTYPE
+#    ifdef WE_MUST_DEAL_WITH_MISMATCHED_CTYPE
     restore_toggled_locale_c(LC_CTYPE, orig_CTYPE_locale);
 #    endif
 
@@ -6883,7 +6905,7 @@ S_strftime_tm(pTHX_ const char *fmt, const struct tm *mytm)
 #ifndef HAS_STRFTIME
     Perl_croak(aTHX_ "panic: no strftime");
 #else
-#  if defined(USE_LOCALE_CTYPE) && defined(USE_LOCALE_TIME)
+#  if defined(WE_MUST_DEAL_WITH_MISMATCHED_CTYPE) && defined(USE_LOCALE_TIME)
 
     const char * orig_CTYPE_LOCALE = toggle_locale_c(LC_CTYPE,
                                                      querylocale_c(LC_TIME));
@@ -6964,7 +6986,7 @@ S_strftime_tm(pTHX_ const char *fmt, const struct tm *mytm)
 
   strftime_return:
 
-#  if defined(USE_LOCALE_CTYPE) && defined(USE_LOCALE_TIME)
+#  if defined(WE_MUST_DEAL_WITH_MISMATCHED_CTYPE) && defined(USE_LOCALE_TIME)
 
     restore_toggled_locale_c(LC_CTYPE, orig_CTYPE_LOCALE);