snprintf: guarantee %1$d, for libintl

Newer mingw (but not yet mingw64) provides two flavors of
snprintf: _snprintf defers straight to msvcrt, which has broken
return value and does not understand %llu or %zu; and snprintf,
which fixes these two bugs but does not understand %1$s.

Libintl specifically favors _snprintf, with broken return value,
even when compiled on mingw with a fixed snprintf, because the
only behavior which it wants to fix is %1$s handling.  But this
means that the replacement libintl_snprintf has a broken return.

If one uses the 'snprintf-posix' module, then the gnulib
replacement kicks in, and does everything that libintl needs, so
on mingw, <libintl.h> specifically avoids overriding snprintf if
it detected that gnulib replaced snprintf.  However, if one only
uses the 'snprintf' module and also uses libintl, this means
there are two problems:

1. The gnulib 'snprintf' module does not replace the mingw
snprintf function, because it has proper return values, while the
libintl.h header knows that %1$d is broken so snprintf must be
replaced, with the end result that the application gets the
libintl replacement snprintf with broken return values in spite
of the gnulib module.

2. Conversely, if the application did '#define snprintf snprintf',
that would be enough to make libintl avoid installing its own
replacement because libintl would see the define as a sign that
gnulib is happy with snprintf.  However, if gnulib didn't enforce
%1$s, users can end up with translated strings that break when
passed to the native snprintf.

Happily, the gnulib snprintf replacement already guarantees %1$s
without needing any further preprocessor macros defined, and
without dragging in the LGPLv3+ bulk of snprintf-posix, so the
problem boils down to guaranteeing that gnulib will replace
snprintf if it lacks %1$s support.  Basically, gnulib must
replace snprintf under all the same conditions as libintl, as
well as any other conditions of its own, if the libintl trick
of deferring to gnulib is to work correctly.

* m4/snprintf.m4 (gl_FUNC_SNPRINTF): Require %1$d support.
* m4/vsnprintf.m4 (gl_FUNC_VSNPRINTF): Likewise.
* doc/posix-functions/snprintf.texi (snprintf): Update.
* doc/posix-functions/vsnprintf.texi (vsnprintf): Likewise.
* tests/test-snprintf.c (main): Enhance test.
* tests/test-vsnprintf.c (main): Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/ChangeLog b/ChangeLog
index e56cd80..71c1560 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2011-07-05  Eric Blake  <eblake@redhat.com>
+
+       snprintf: guarantee %1$d, for libintl
+       * m4/snprintf.m4 (gl_FUNC_SNPRINTF): Require %1$d support.
+       * m4/vsnprintf.m4 (gl_FUNC_VSNPRINTF): Likewise.
+       * doc/posix-functions/snprintf.texi (snprintf): Update.
+       * doc/posix-functions/vsnprintf.texi (vsnprintf): Likewise.
+       * tests/test-snprintf.c (main): Enhance test.
+       * tests/test-vsnprintf.c (main): Likewise.
+
 2011-07-05  Jim Meyering  <meyering@redhat.com>
 
        maint: exempt stdio-read.c and stdio-write.c from the cppi check

diff --git a/doc/posix-functions/snprintf.texi b/doc/posix-functions/snprintf.texi
index d295cea..4e7a294 100644 (file)
--- a/doc/posix-functions/snprintf.texi
+++ b/doc/posix-functions/snprintf.texi
@@ -12,12 +12,17 @@ Portability problems fixed by either Gnulib module @code{snprintf} or @code{snpr
 This function is missing on some platforms:
 IRIX 5.3, OSF/1 4.0, Solaris 2.5.1.
 @item
-This function does not return a byte count as specified in C99 on some platforms:
+This function does not support format directives that access arguments in an
+arbitrary order, such as @code{"%2$s"}, on some platforms:
+NetBSD 3.0, mingw, BeOS.
+@item
+This function does not return a byte count as specified in C99 on some
+platforms:
 HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 9, mingw.
 @item
 This function overwrites memory even when a size argument of 1 is passed on some
 platforms:
-Linux libc5.
+Linux libc5, BeOS.
 @end itemize
 
 Portability problems fixed by Gnulib module @code{snprintf-posix}:
@@ -50,10 +55,6 @@ This function does not support precisions in the @samp{ls} directive correctly
 on some platforms:
 Solaris 11 2010-11.
 @item
-This function does not support format directives that access arguments in an
-arbitrary order, such as @code{"%2$s"}, on some platforms:
-NetBSD 3.0, mingw, BeOS.
-@item
 This function doesn't support the @code{'} flag on some platforms:
 NetBSD 3.0, Cygwin 1.5.24, mingw.
 @item
@@ -83,10 +84,6 @@ mingw.
 This function does not fully support the @samp{n} directive on some platforms:
 HP-UX 11, mingw.
 @item
-This function overwrites memory when a size = 1 argument is passed on some
-platforms:
-BeOS.
-@item
 This function overwrites memory even when a zero size argument is passed on some
 platforms:
 OSF/1 5.1.

diff --git a/doc/posix-functions/vsnprintf.texi b/doc/posix-functions/vsnprintf.texi
index e391f35..ca6e092 100644 (file)
--- a/doc/posix-functions/vsnprintf.texi
+++ b/doc/posix-functions/vsnprintf.texi
@@ -12,11 +12,16 @@ Portability problems fixed by either Gnulib module @code{vsnprintf} or @code{vsn
 This function is missing on some platforms:
 IRIX 5.3, OSF/1 4.0, Solaris 2.5.1.
 @item
+This function does not support format directives that access arguments in an
+arbitrary order, such as @code{"%2$s"}, on some platforms:
+NetBSD 3.0, mingw, BeOS.
+@item
 This function overwrites memory even when a size argument of 1 is passed on some
 platforms:
-Linux libc5.
+Linux libc5, BeOS.
 @item
-This function does not return a byte count as specified in C99 on some platforms:
+This function does not return a byte count as specified in C99 on some
+platforms:
 HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 9, mingw.
 @end itemize
 
@@ -50,10 +55,6 @@ This function does not support precisions in the @samp{ls} directive correctly
 on some platforms:
 Solaris 11 2010-11.
 @item
-This function does not support format directives that access arguments in an
-arbitrary order, such as @code{"%2$s"}, on some platforms:
-NetBSD 3.0, mingw, BeOS.
-@item
 This function doesn't support the @code{'} flag on some platforms:
 NetBSD 3.0, Cygwin 1.5.24, mingw.
 @item
@@ -83,10 +84,6 @@ mingw.
 This function does not fully support the @samp{n} directive on some platforms:
 HP-UX 11, mingw.
 @item
-This function overwrites memory when a size = 1 argument is passed on some
-platforms:
-BeOS.
-@item
 This function overwrites memory even when a zero size argument is passed on some
 platforms:
 HP-UX 11, OSF/1 5.1.

diff --git a/m4/snprintf.m4 b/m4/snprintf.m4
index 8aa5dbe..6f71623 100644 (file)
--- a/m4/snprintf.m4
+++ b/m4/snprintf.m4
@@ -1,9 +1,13 @@
-# snprintf.m4 serial 5
+# snprintf.m4 serial 6
 dnl Copyright (C) 2002-2004, 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
+dnl Libintl 0.17 will replace snprintf only if it does not support %1$s,
+dnl but defers to any gnulib snprintf replacements.  Therefore, gnulib
+dnl must guarantee that the decision for replacing snprintf is a superset
+dnl of the reasons checked by libintl.
 AC_DEFUN([gl_FUNC_SNPRINTF],
 [
   AC_REQUIRE([gl_STDIO_H_DEFAULTS])
@@ -16,7 +20,12 @@ AC_DEFUN([gl_FUNC_SNPRINTF],
         gl_SNPRINTF_RETVAL_C99
         case "$gl_cv_func_snprintf_retval_c99" in
           *yes)
-            gl_cv_func_snprintf_usable=yes
+            gl_PRINTF_POSITIONS
+            case "$gl_cv_func_printf_positions" in
+              *yes)
+                gl_cv_func_snprintf_usable=yes
+                ;;
+            esac
             ;;
         esac
         ;;

diff --git a/m4/vsnprintf.m4 b/m4/vsnprintf.m4
index e4725e4..d6ce1e6 100644 (file)
--- a/m4/vsnprintf.m4
+++ b/m4/vsnprintf.m4
@@ -1,9 +1,13 @@
-# vsnprintf.m4 serial 5
+# vsnprintf.m4 serial 6
 dnl Copyright (C) 2002-2004, 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
+dnl Libintl 0.17 will replace vsnprintf only if it does not support %1$s,
+dnl but defers to any gnulib vsnprintf replacements.  Therefore, gnulib
+dnl must guarantee that the decision for replacing vsnprintf is a superset
+dnl of the reasons checked by libintl.
 AC_DEFUN([gl_FUNC_VSNPRINTF],
 [
   AC_REQUIRE([gl_STDIO_H_DEFAULTS])
@@ -16,7 +20,12 @@ AC_DEFUN([gl_FUNC_VSNPRINTF],
         gl_SNPRINTF_RETVAL_C99
         case "$gl_cv_func_snprintf_retval_c99" in
           *yes)
-            gl_cv_func_vsnprintf_usable=yes
+            gl_PRINTF_POSITIONS
+            case "$gl_cv_func_printf_positions" in
+              *yes)
+                gl_cv_func_vsnprintf_usable=yes
+                ;;
+            esac
             ;;
         esac
         ;;

diff --git a/tests/test-snprintf.c b/tests/test-snprintf.c
index 95a352d..18efed5 100644 (file)
--- a/tests/test-snprintf.c
+++ b/tests/test-snprintf.c
@@ -60,5 +60,13 @@ main (int argc, char *argv[])
         }
     }
 
+  /* Test the support of the POSIX/XSI format strings with positions.  */
+  {
+    char result[100];
+    int retval = snprintf (result, sizeof (result), "%2$d %1$d", 33, 55);
+    ASSERT (strcmp (result, "55 33") == 0);
+    ASSERT (retval == strlen (result));
+  }
+
   return 0;
 }

diff --git a/tests/test-vsnprintf.c b/tests/test-vsnprintf.c
index 5060836..6711f39 100644 (file)
--- a/tests/test-vsnprintf.c
+++ b/tests/test-vsnprintf.c
@@ -73,5 +73,13 @@ main (int argc, char *argv[])
         }
     }
 
+  /* Test the support of the POSIX/XSI format strings with positions.  */
+  {
+    char result[100];
+    int retval = my_snprintf (result, sizeof (result), "%2$d %1$d", 33, 55);
+    ASSERT (strcmp (result, "55 33") == 0);
+    ASSERT (retval == strlen (result));
+  }
+
   return 0;
 }