[PATCHv2] stdio: don't assume gets any more

[Eric Blake]

Gnulib intentionally does not have a gets module, and now that C11
and glibc have dropped it, we should be more proactive about warning
any user on a platform that still has a declaration of this dangerous
interface.

* m4/stdio_h.m4 (gl_STDIO_H, gl_STDIO_H_DEFAULTS): Drop gets
support.
* modules/stdio (Makefile.am): Likewise.
* lib/stdio-read.c (gets): Likewise.
* tests/test-stdio-c++.cc: Likewise.
* lib/stdio.in.h (gets): Make warning occur in more places.
* doc/posix-functions/gets.texi (gets): Update documentation.
Reported by Christer Solskogen.

Signed-off-by: Eric Blake <address@hidden>
---

I think this picks up on all of Paul's helpful review comments.

 ChangeLog                     |   12 ++++++++++++
 doc/posix-functions/gets.texi |   14 +++++++-------
 lib/stdio-read.c              |    8 +-------
 lib/stdio.in.h                |   26 +++++++-------------------
 m4/stdio_h.m4                 |   10 ++++------
 modules/stdio                 |    1 -
 tests/test-stdio-c++.cc       |    4 +---
 7 files changed, 32 insertions(+), 43 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index d74544a..0a9bf78 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2012-03-29  Eric Blake  <address@hidden>
+
+       stdio: don't assume gets any more
+       * m4/stdio_h.m4 (gl_STDIO_H, gl_STDIO_H_DEFAULTS): Drop gets
+       support.
+       * modules/stdio (Makefile.am): Likewise.
+       * lib/stdio-read.c (gets): Likewise.
+       * tests/test-stdio-c++.cc: Likewise.
+       * lib/stdio.in.h (gets): Make warning occur in more places.
+       * doc/posix-functions/gets.texi (gets): Update documentation.
+       Reported by Christer Solskogen.
+
 2012-03-25  Bruno Haible  <address@hidden>

        Tests for module 'localeconv'.
diff --git a/doc/posix-functions/gets.texi b/doc/posix-functions/gets.texi
index cf2716a..dc80dda 100644
--- a/doc/posix-functions/gets.texi
+++ b/doc/posix-functions/gets.texi
@@ -4,15 +4,10 @@ gets

 POSIX specification:@* 
@url{http://www.opengroup.org/onlinepubs/9699919799/functions/gets.html}

-Gnulib module: stdio, nonblocking
+Gnulib module: ---

-Portability problems fixed by Gnulib module @code{stdio}, together with module 
@code{nonblocking}:
+Portability problems fixed by Gnulib:
 @itemize
address@hidden
-When reading from a non-blocking pipe whose buffer is empty, this function
-fails with @code{errno} being set to @code{EINVAL} instead of @code{EAGAIN} on
-some platforms:
-mingw, MSVC 9.
 @end itemize

 Portability problems not fixed by Gnulib:
@@ -20,6 +15,11 @@ gets
 @item
 This function should never be used, because it can overflow any given buffer.
 @item
+When reading from a non-blocking pipe whose buffer is empty, this function
+fails with @code{errno} being set to @code{EINVAL} instead of @code{EAGAIN} on
+some platforms:
+mingw, MSVC 9.
address@hidden
 On Windows platforms (excluding Cygwin), this function does not set 
@code{errno}
 upon failure.
 @end itemize
diff --git a/lib/stdio-read.c b/lib/stdio-read.c
index 9155a0b..358d8cd 100644
--- a/lib/stdio-read.c
+++ b/lib/stdio-read.c
@@ -131,13 +131,7 @@ fgets (char *s, int n, FILE *stream)
   CALL_WITH_ERRNO_FIX (char *, fgets (s, n, stream), ret == NULL)
 }

-char *
-gets (char *s)
-#undef gets
-{
-  FILE *stream = stdin;
-  CALL_WITH_ERRNO_FIX (char *, gets (s), ret == NULL)
-}
+/* We intentionally don't bother to fix gets.  */

 size_t
 fread (void *ptr, size_t s, size_t n, FILE *stream)
diff --git a/lib/stdio.in.h b/lib/stdio.in.h
index aa7b599..2cdee26 100644
--- a/lib/stdio.in.h
+++ b/lib/stdio.in.h
@@ -698,26 +698,14 @@ _GL_WARN_ON_USE (getline, "getline is unportable - "
 # endif
 #endif

-#if @GNULIB_GETS@
-# if @REPLACE_STDIO_READ_FUNCS@ && @GNULIB_STDIO_H_NONBLOCKING@
-#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
-#   undef gets
-#   define gets rpl_gets
-#  endif
-_GL_FUNCDECL_RPL (gets, char *, (char *s) _GL_ARG_NONNULL ((1)));
-_GL_CXXALIAS_RPL (gets, char *, (char *s));
-# else
-_GL_CXXALIAS_SYS (gets, char *, (char *s));
-#  undef gets
-# endif
-_GL_CXXALIASWARN (gets);
 /* It is very rare that the developer ever has full control of stdin,
-   so any use of gets warrants an unconditional warning.  Assume it is
-   always declared, since it is required by C89.  */
+   so any use of gets warrants an unconditional warning; besides, C11
+   removed it.  */
+#undef gets
+#if HAVE_RAW_DECL_GETS
 _GL_WARN_ON_USE (gets, "gets is a security hole - use fgets instead");
 #endif

-
 #if @GNULIB_OBSTACK_PRINTF@ || @GNULIB_OBSTACK_PRINTF_POSIX@
 struct obstack;
 /* Grow an obstack with formatted output.  Return the number of
@@ -1053,9 +1041,9 @@ _GL_WARN_ON_USE (snprintf, "snprintf is unportable - "
 # endif
 #endif

-/* Some people would argue that sprintf should be handled like gets
-   (for example, OpenBSD issues a link warning for both functions),
-   since both can cause security holes due to buffer overruns.
+/* Some people would argue that all sprintf uses should be warned about
+   (for example, OpenBSD issues a link warning for it),
+   since it can cause security holes due to buffer overruns.
    However, we believe that sprintf can be used safely, and is more
    efficient than snprintf in those safe cases; and as proof of our
    belief, we use sprintf in several gnulib modules.  So this header
diff --git a/m4/stdio_h.m4 b/m4/stdio_h.m4
index 1973e8d..b03393b 100644
--- a/m4/stdio_h.m4
+++ b/m4/stdio_h.m4
@@ -1,4 +1,4 @@
-# stdio_h.m4 serial 40
+# stdio_h.m4 serial 41
 dnl Copyright (C) 2007-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -18,7 +18,6 @@ AC_DEFUN([gl_STDIO_H],
   GNULIB_GETC=1
   GNULIB_GETCHAR=1
   GNULIB_FGETS=1
-  GNULIB_GETS=1
   GNULIB_FREAD=1
   dnl This ifdef is necessary to avoid an error "missing file lib/stdio-read.c"
   dnl "expected source file, required through AC_LIBSOURCES, not found". It is
@@ -72,10 +71,10 @@ AC_DEFUN([gl_STDIO_H],

   dnl Check for declarations of anything we want to poison if the
   dnl corresponding gnulib module is not in use, and which is not
-  dnl guaranteed by C89.
+  dnl guaranteed by both C89 and C11.
   gl_WARN_ON_USE_PREPARE([[#include <stdio.h>
-    ]], [dprintf fpurge fseeko ftello getdelim getline pclose popen renameat
-    snprintf tmpfile vdprintf vsnprintf])
+    ]], [dprintf fpurge fseeko ftello getdelim getline gets pclose popen
+    renameat snprintf tmpfile vdprintf vsnprintf])
 ])

 AC_DEFUN([gl_STDIO_MODULE_INDICATOR],
@@ -113,7 +112,6 @@ AC_DEFUN([gl_STDIO_H_DEFAULTS],
   GNULIB_GETCHAR=0;              AC_SUBST([GNULIB_GETCHAR])
   GNULIB_GETDELIM=0;             AC_SUBST([GNULIB_GETDELIM])
   GNULIB_GETLINE=0;              AC_SUBST([GNULIB_GETLINE])
-  GNULIB_GETS=0;                 AC_SUBST([GNULIB_GETS])
   GNULIB_OBSTACK_PRINTF=0;       AC_SUBST([GNULIB_OBSTACK_PRINTF])
   GNULIB_OBSTACK_PRINTF_POSIX=0; AC_SUBST([GNULIB_OBSTACK_PRINTF_POSIX])
   GNULIB_PCLOSE=0;               AC_SUBST([GNULIB_PCLOSE])
diff --git a/modules/stdio b/modules/stdio
index 2e094b8..a389440 100644
--- a/modules/stdio
+++ b/modules/stdio
@@ -53,7 +53,6 @@ stdio.h: stdio.in.h $(top_builddir)/config.status 
$(CXXDEFS_H) $(ARG_NONNULL_H)
              -e 's/@''GNULIB_GETCHAR''@/$(GNULIB_GETCHAR)/g' \
              -e 's/@''GNULIB_GETDELIM''@/$(GNULIB_GETDELIM)/g' \
              -e 's/@''GNULIB_GETLINE''@/$(GNULIB_GETLINE)/g' \
-             -e 's/@''GNULIB_GETS''@/$(GNULIB_GETS)/g' \
              -e 's/@''GNULIB_OBSTACK_PRINTF''@/$(GNULIB_OBSTACK_PRINTF)/g' \
              -e 
's/@''GNULIB_OBSTACK_PRINTF_POSIX''@/$(GNULIB_OBSTACK_PRINTF_POSIX)/g' \
              -e 's/@''GNULIB_PCLOSE''@/$(GNULIB_PCLOSE)/g' \
diff --git a/tests/test-stdio-c++.cc b/tests/test-stdio-c++.cc
index 699e2de..6400448 100644
--- a/tests/test-stdio-c++.cc
+++ b/tests/test-stdio-c++.cc
@@ -122,9 +122,7 @@ SIGNATURE_CHECK (GNULIB_NAMESPACE::getline, ssize_t,
                  (char **, size_t *, FILE *));
 #endif

-#if GNULIB_TEST_GETS
-SIGNATURE_CHECK (GNULIB_NAMESPACE::gets, char *, (char *));
-#endif
+/* Don't bother testing gets; it should never be used.  */

 #if GNULIB_TEST_OBSTACK_PRINTF || GNULIB_TEST_OBSTACK_PRINTF_POSIX
 SIGNATURE_CHECK (GNULIB_NAMESPACE::obstack_printf, int,
-- 
1.7.7.6