[newlib-cygwin] Fix duplocale (libc/locale/duplocale.c) which fails to properly call __loadlocale

[newlib-cygwin] Fix duplocale (libc/locale/duplocale.c) which fails to properly call __loadlocale

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=973f766f6e3f750784ea95de23bb4d1745854d4e

commit 973f766f6e3f750784ea95de23bb4d1745854d4e
Author: Koichi Murase <myoga.murase@gmail.com>
Date:   Sun Mar 12 01:27:26 2017 +0900

    Fix duplocale (libc/locale/duplocale.c) which fails to properly call __loadlocale
    
    Problem:
    
      After  passing  locales  created  by  'duplocale'   to   'uselocale',
      referencing   'MB_CUR_MAX',   which   is   actually   expanded    to
      '__locale_mb_cur_max()' by preprocessors, causes segmentation faults.
      Direct use of locales from 'newlocale' does not  cause  the  problem.
      This is the problem of 'duplocale'.
    
      $ echo $LANG
      ja_JP.UTF-8
      $ cat test.c
      #include <stdlib.h>
      #include <locale.h>
    
      volatile int var;
    
      int main(void) {
        locale_t const loc = newlocale(LC_ALL_MASK, "", NULL);
        locale_t const dup = duplocale(loc);
        locale_t const old = uselocale(dup);
        var = MB_CUR_MAX; /* <-- crashes here */
        uselocale(old);
        freelocale(dup);
        freelocale(loc);
        return 0;
      }
      $ gcc test.c
      $ ./a
      Segmentation fault (core dumped)
    
      # Note: "core dumped" in the above message was  actually written  in
      # Japanese, but I translated the part to post a mail in English.
    
    Bug:
    
      In the beginning of '__loadlocale' (newlib/libc/locale/locale.c:501),
      there is a code which checks if the operations can be skipped:
    
      > /* Avoid doing everything twice if nothing has changed. */
      > if (!strcmp (new_locale, loc->categories[category]))
      >   return loc->categories[category];
    
      While,   in   the   function   '_duplocale_r'    (newlib/libc/locale/
      duplocale.c), '__loadlocale'  is  called  as  in  the  quoted  codes:
    
      > /* If the object is not a "C" locale category, copy it.  Just call
      >    __loadlocale.  It knows what to do to replicate the category. */
      > tmp_locale.lc_cat[i].ptr = NULL;
      > tmp_locale.lc_cat[i].buf = NULL;
      > if (!__loadlocale (&tmp_locale, i, tmp_locale.categories[i]))
      >   goto error;
    
      This call of '__loadlocale' results in the skip check being
    
        !strcmp(tmp_locale.categories[i], tmp_locale.categories[i]),
    
      which is always true. This  means  that  the  actual  operations  of
      '__loadLocale' will never be performed for 'duplocale'.
    
    Fix:
    
      The call of '__loadlocale' in '_duplocale_r' is modified.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 newlib/libc/locale/duplocale.c | 3 ++-
 newlib/libc/locale/locale.c    | 6 +++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/newlib/libc/locale/duplocale.c b/newlib/libc/locale/duplocale.c
index 06ebfcd..9f6156c 100644
--- a/newlib/libc/locale/duplocale.c
+++ b/newlib/libc/locale/duplocale.c
@@ -64,7 +64,8 @@ _duplocale_r (struct _reent *p, struct __locale_t *locobj)
 	   __loadlocale.  It knows what to do to replicate the category. */
 	tmp_locale.lc_cat[i].ptr = NULL;
 	tmp_locale.lc_cat[i].buf = NULL;
-	if (!__loadlocale (&tmp_locale, i, tmp_locale.categories[i]))
+	tmp_locale.categories[i][0] = '\0';	/* __loadlocale tests this! */
+	if (!__loadlocale (&tmp_locale, i, locobj->categories[i]))
 	  goto error;
       }
 #endif /* __HAVE_LOCALE_INFO__ */
diff --git a/newlib/libc/locale/locale.c b/newlib/libc/locale/locale.c
index 8572821..b540237 100644
--- a/newlib/libc/locale/locale.c
+++ b/newlib/libc/locale/locale.c
@@ -498,7 +498,11 @@ __loadlocale (struct __locale_t *loc, int category, const char *new_locale)
   mbtowc_p l_mbtowc;
   int cjknarrow = 0;
 
-  /* Avoid doing everything twice if nothing has changed. */
+  /* Avoid doing everything twice if nothing has changed.
+
+     duplocale relies on this test to go wrong so the locale is actually
+     duplicated when required.  Any change here has to be synced with a
+     matching change in duplocale. */
   if (!strcmp (new_locale, loc->categories[category]))
     return loc->categories[category];