Re: new module 'mbsrtowcs'

[Bruno Haible]

>       New module 'mbsrtowcs'.

There is a portability problem, due to incomplete specification of the function
in ISO C 99. This patch documents it.


2008-12-21  Bruno Haible  <br...@clisp.org>

        Work around a portability problem.
        * tests/test-mbsrtowcs.c (main): Use a temporary conversion state.
        * doc/posix-functions/mbsrtowcs.texi: Document the portability problem.

--- doc/posix-functions/mbsrtowcs.texi.orig     2008-12-21 12:02:22.000000000 
+0100
+++ doc/posix-functions/mbsrtowcs.texi  2008-12-21 11:50:37.000000000 +0100
@@ -18,4 +18,11 @@
 @item
 On Windows platforms, @code{wchar_t} is a 16-bit type and therefore cannot
 accommodate all Unicode characters.
+...@item
+The specification is not clear about whether this function should update the
+conversion state when the first argument (the destination pointer) is NULL.
+The glibc implementation does not update the state in this case; the MacOS X
+and FreeBSD implementations do.
+For portability, when passing a NULL destination argument, it is best to pass
+a pointer to a temporary copy of the conversion state.
 @end itemize
--- tests/test-mbsrtowcs.c.orig 2008-12-21 12:02:22.000000000 +0100
+++ tests/test-mbsrtowcs.c      2008-12-21 11:53:07.000000000 +0100
@@ -88,6 +88,7 @@
          #define BUFSIZE 10
          wchar_t buf[BUFSIZE];
          const char *src;
+         mbstate_t temp_state;
 
          {
            size_t i;
@@ -118,7 +119,8 @@
                input[1] = '\0';
 
                src = input + 2;
-               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 1, &state);
+               temp_state = state;
+               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 1, 
&temp_state);
                ASSERT (ret == 3);
                ASSERT (src == input + 2);
                ASSERT (mbsinit (&state));
@@ -162,7 +164,8 @@
                input[1] = '\0';
 
                src = input + 2;
-               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 2, &state);
+               temp_state = state;
+               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 2, 
&temp_state);
                ASSERT (ret == 4);
                ASSERT (src == input + 2);
                ASSERT (!mbsinit (&state));
@@ -215,7 +218,8 @@
                input[3] = '\0';
 
                src = input + 4;
-               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 2, &state);
+               temp_state = state;
+               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 2, 
&temp_state);
                ASSERT (ret == 3);
                ASSERT (src == input + 4);
                ASSERT (!mbsinit (&state));
@@ -259,7 +263,8 @@
                input[1] = '\0';
 
                src = input + 2;
-               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 2, &state);
+               temp_state = state;
+               ret = mbsrtowcs (NULL, &src, unlimited ? BUFSIZE : 2, 
&temp_state);
                ASSERT (ret == 4);
                ASSERT (src == input + 2);
                ASSERT (!mbsinit (&state));