From 973f766f6e3f750784ea95de23bb4d1745854d4e Mon Sep 17 00:00:00 2001
From: Koichi Murase <myoga.murase@gmail.com>
Date: Sun, 12 Mar 2017 01:27:26 +0900
Subject: [PATCH] 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>
---
 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 06ebfcd6e..9f6156cb4 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 857282105..b5402372c 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];