forkpty, openpty: prefer glibc's const-safe prototype

This silences a compiler warning for test-forkpty.c.

* lib/forkpty.c (rpl_forkpty): New file.
* lib/openpty.c (rpl_openpty): Likewise.
* modules/forkpty (Files): Distribute it.
* modules/openpty (Files): Likewise.
* m4/pty_h.m4 (gl_PTY_H_DEFAULTS): Add new witnesses.  Move decl
check...
* m4/pty.m4 (gl_FORKPTY, gl_OPENPTY): ...here.  Request
replacement for for non-const BSD signature.
* modules/pty (Makefile.am): Substitute witnesses.
* lib/pty.in.h (forkpty, openpty): Declare replacements.
* tests/test-forkpty.c: Update signature check.
* tests/test-openpty.c: Likewise.
* doc/glibc-functions/forkpty.texi (forkpty): Document the fix.
* doc/glibc-functions/openpty.texi (openpty): Likewise.
Reported by Bruno Haible.

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

12 files changed, 218 insertions, 16 deletions

diff --git a/ChangeLog b/ChangeLog
index 8c1820aa80..b42d244c70 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,21 @@
 2010-03-19  Eric Blake  <eblake@redhat.com>
 
+	forkpty, openpty: prefer glibc's const-safe prototype
+	* lib/forkpty.c (rpl_forkpty): New file.
+	* lib/openpty.c (rpl_openpty): Likewise.
+	* modules/forkpty (Files): Distribute it.
+	* modules/openpty (Files): Likewise.
+	* m4/pty_h.m4 (gl_PTY_H_DEFAULTS): Add new witnesses.  Move decl
+	check...
+	* m4/pty.m4 (gl_FORKPTY, gl_OPENPTY): ...here.  Request
+	replacement for for non-const BSD signature.
+	* modules/pty (Makefile.am): Substitute witnesses.
+	* lib/pty.in.h (forkpty, openpty): Declare replacements.
+	* tests/test-forkpty.c: Update signature check.
+	* tests/test-openpty.c: Likewise.
+	* doc/glibc-functions/forkpty.texi (forkpty): Document the fix.
+	* doc/glibc-functions/openpty.texi (openpty): Likewise.
+
 	forkpty, openpty: split functions into new modules
 	* modules/pty (Makefile.am): Substitute new witnesses.
 	(Libraries): Move library detection...
diff --git a/doc/glibc-functions/forkpty.texi b/doc/glibc-functions/forkpty.texi
index 8a86511585..aecc2329e2 100644
--- a/doc/glibc-functions/forkpty.texi
+++ b/doc/glibc-functions/forkpty.texi
@@ -16,6 +16,10 @@ required.
 The function is declared in pty.h on Cygwin, Interix, OSF/1 4 and 5,
 and glibc.  It is declared in util.h on Mac OS X, OpenBSD and NetBSD.
 It is declared in libutil.h on FreeBSD.
+@item
+Some platforms declare the function without marking the last two
+parameters @code{const}.
+FreeBSD, Cygwin 1.7.1.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/doc/glibc-functions/openpty.texi b/doc/glibc-functions/openpty.texi
index 7eb528efd4..5eb57c353a 100644
--- a/doc/glibc-functions/openpty.texi
+++ b/doc/glibc-functions/openpty.texi
@@ -16,6 +16,10 @@ required.
 The function is declared in pty.h on Cygwin, Interix, OSF/1 4 and 5,
 and glibc.  It is declared in util.h on Mac OS X, OpenBSD and NetBSD.
 It is declared in libutil.h on FreeBSD.
+@item
+Some platforms declare the function without marking the last two
+parameters @code{const}.
+FreeBSD, Cygwin 1.7.1.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/lib/forkpty.c b/lib/forkpty.c
new file mode 100644
index 0000000000..adbc3d5518
--- /dev/null
+++ b/lib/forkpty.c
@@ -0,0 +1,35 @@
+/* Fork a child attached to a pseudo-terminal descriptor.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <pty.h>
+
+#if HAVE_DECL_FORKPTY
+# undef forkpty
+int
+rpl_forkpty (int *amaster, char *name, struct termios const *termp,
+         struct winsize const *winp)
+{
+  /* Cast away const, for implementations with weaker prototypes.  */
+  return forkpty (amaster, name, (struct termios *) termp,
+                  (struct winsize *) winp);
+}
+#else
+# error forkpty has not been ported to your system; \
+  report this to bug-gnulib@gnu.org for help
+#endif
diff --git a/lib/openpty.c b/lib/openpty.c
new file mode 100644
index 0000000000..e7eb46d464
--- /dev/null
+++ b/lib/openpty.c
@@ -0,0 +1,35 @@
+/* Open a pseudo-terminal descriptor.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <pty.h>
+
+#if HAVE_DECL_OPENPTY
+# undef openpty
+int
+rpl_openpty (int *amaster, int *aslave, char *name, struct termios const *termp,
+         struct winsize const *winp)
+{
+  /* Cast away const, for implementations with weaker prototypes.  */
+  return openpty (amaster, aslave, name, (struct termios *) termp,
+                  (struct winsize *) winp);
+}
+#else
+# error openpty has not been ported to your system; \
+  report this to bug-gnulib@gnu.org for help
+#endif
diff --git a/lib/pty.in.h b/lib/pty.in.h
index 1b7bf82055..2780d6141c 100644
--- a/lib/pty.in.h
+++ b/lib/pty.in.h
@@ -45,6 +45,23 @@
 /* Declare overridden functions.  */
 
 #if @GNULIB_FORKPTY@
+# if @REPLACE_FORKPTY@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   undef forkpty
+#   define forkpty rpl_forkpty
+#  endif
+_GL_FUNCDECL_RPL (forkpty, int,
+                  (int *, char *, struct termios const *,
+                   struct winsize const *));
+_GL_CXXALIAS_RPL (forkpty, int,
+                  (int *, char *, struct termios const *,
+                   struct winsize const *));
+# else
+_GL_CXXALIAS_SYS (forkpty, int,
+                  (int *, char *, struct termios const *,
+                   struct winsize const *));
+# endif
+_GL_CXXALIASWARN (forkpty);
 #elif defined GNULIB_POSIXCHECK
 # undef forkpty
 # if HAVE_RAW_DECL_FORKPTY
@@ -54,6 +71,23 @@ _GL_WARN_ON_USE (forkpty, "forkpty is not declared consistently - "
 #endif
 
 #if @GNULIB_OPENPTY@
+# if @REPLACE_OPENPTY@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   undef openpty
+#   define openpty rpl_openpty
+#  endif
+_GL_FUNCDECL_RPL (openpty, int,
+                  (int *, int *, char *, struct termios const *,
+                   struct winsize const *));
+_GL_CXXALIAS_RPL (openpty, int,
+                  (int *, int *, char *, struct termios const *,
+                   struct winsize const *));
+# else
+_GL_CXXALIAS_SYS (openpty, int,
+                  (int *, int *, char *, struct termios const *,
+                   struct winsize const *));
+# endif
+_GL_CXXALIASWARN (openpty);
 #elif defined GNULIB_POSIXCHECK
 # undef openpty
 # if HAVE_RAW_DECL_OPENPTY
diff --git a/m4/pty.m4 b/m4/pty.m4
index f2a5664f84..d2f8110f13 100644
--- a/m4/pty.m4
+++ b/m4/pty.m4
@@ -1,4 +1,4 @@
-# pty.m4 serial 1
+# pty.m4 serial 2
 dnl Copyright (C) 2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -23,9 +23,89 @@ AC_DEFUN([gl_PTY_LIB],
 AC_DEFUN([gl_FORKPTY],
 [
   AC_REQUIRE([gl_PTY_LIB])
+  AC_REQUIRE([gl_PTY])
+
+  AC_CHECK_DECLS([forkpty],,, [[
+#if HAVE_PTY_H
+# include <pty.h>
+#endif
+#if HAVE_UTIL_H
+# include <util.h>
+#endif
+#if HAVE_LIBUTIL_H
+# include <libutil.h>
+#endif
+]])
+  if test $ac_cv_have_decl_forkpty = no; then
+    AC_MSG_WARN([[Cannot find forkpty, build will likely fail]])
+  fi
+
+  dnl Prefer glibc's const-safe prototype, if available.
+  AC_CACHE_CHECK([for const-safe forkpty signature],
+    [gl_cv_func_forkpty_const],
+    [AC_COMPILE_IFELSE(
+      [AC_LANG_PROGRAM([[
+#if HAVE_PTY_H
+# include <pty.h>
+#endif
+#if HAVE_UTIL_H
+# include <util.h>
+#endif
+#if HAVE_LIBUTIL_H
+# include <libutil.h>
+#endif
+      ]], [[
+        int forkpty (int *, char *, struct termios const *,
+                     struct winsize const *);
+      ]])],
+      [gl_cv_func_forkpty_const=yes], [gl_cv_func_forkpty_const=no])])
+  if test $gl_cv_func_forkpty_const != yes; then
+    REPLACE_FORKPTY=1
+    AC_LIBOBJ([forkpty])
+  fi
 ])
 
 AC_DEFUN([gl_OPENPTY],
 [
   AC_REQUIRE([gl_PTY_LIB])
+  AC_REQUIRE([gl_PTY])
+
+  AC_CHECK_DECLS([openpty],,, [[
+#if HAVE_PTY_H
+# include <pty.h>
+#endif
+#if HAVE_UTIL_H
+# include <util.h>
+#endif
+#if HAVE_LIBUTIL_H
+# include <libutil.h>
+#endif
+]])
+  if test $ac_cv_have_decl_openpty = no; then
+    AC_MSG_WARN([[Cannot find openpty, build will likely fail]])
+  fi
+
+  dnl Prefer glibc's const-safe prototype, if available.
+  AC_CACHE_CHECK([for const-safe openpty signature],
+    [gl_cv_func_openpty_const],
+    [AC_COMPILE_IFELSE(
+      [AC_LANG_PROGRAM([[
+#if HAVE_PTY_H
+# include <pty.h>
+#endif
+#if HAVE_UTIL_H
+# include <util.h>
+#endif
+#if HAVE_LIBUTIL_H
+# include <libutil.h>
+#endif
+      ]], [[
+        int openpty (int *, int *, char *, struct termios const *,
+                     struct winsize const *);
+      ]])],
+      [gl_cv_func_openpty_const=yes], [gl_cv_func_openpty_const=no])])
+  if test $gl_cv_func_openpty_const != yes; then
+    REPLACE_OPENPTY=1
+    AC_LIBOBJ([openpty])
+  fi
 ])
diff --git a/m4/pty_h.m4 b/m4/pty_h.m4
index 05ac3575c4..cf41eab814 100644
--- a/m4/pty_h.m4
+++ b/m4/pty_h.m4
@@ -1,4 +1,4 @@
-# pty_h.m4 serial 3
+# pty_h.m4 serial 4
 dnl Copyright (C) 2009, 2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -22,18 +22,6 @@ AC_DEFUN_ONCE([gl_PTY],
     if test $ac_cv_header_libutil_h = yes; then
       HAVE_LIBUTIL_H=1
     fi
-    dnl FIXME - move this into forkpty module, when replacement is provided
-    AC_CHECK_DECLS([forkpty],,, [[
-#if HAVE_UTIL_H
-# include <util.h>
-#endif
-#if HAVE_LIBUTIL_H
-# include <libutil.h>
-#endif
-]])
-    if test $ac_cv_have_decl_forkpty = no; then
-      AC_MSG_WARN([[Cannot find forkpty, build will likely fail]])
-    fi
   else # Have <pty.h>, assume forkpty is declared there.
     HAVE_PTY_H=1
   fi
@@ -70,4 +58,6 @@ AC_DEFUN([gl_PTY_H_DEFAULTS],
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_UTIL_H=0;        AC_SUBST([HAVE_UTIL_H])
   HAVE_LIBUTIL_H=0;     AC_SUBST([HAVE_LIBUTIL_H])
+  REPLACE_FORKPTY=0;    AC_SUBST([REPLACE_FORKPTY])
+  REPLACE_OPENPTY=0;    AC_SUBST([REPLACE_OPENPTY])
 ])
diff --git a/modules/forkpty b/modules/forkpty
index 5bfe0a5dea..8fcb382196 100644
--- a/modules/forkpty
+++ b/modules/forkpty
@@ -2,6 +2,7 @@ Description:
 Provide the forkpty() function.
 
 Files:
+lib/forkpty.c
 m4/pty.m4
 
 Depends-on:
diff --git a/modules/openpty b/modules/openpty
index 68e00db4a6..1608a8da47 100644
--- a/modules/openpty
+++ b/modules/openpty
@@ -2,6 +2,7 @@ Description:
 Provide the openpty() function.
 
 Files:
+lib/openpty.c
 m4/pty.m4
 
 Depends-on:
diff --git a/modules/pty b/modules/pty
index 8ea7ed3e32..9020a1a281 100644
--- a/modules/pty
+++ b/modules/pty
@@ -29,6 +29,8 @@ pty.h: pty.in.h $(CXXDEFS_H) $(WARN_ON_USE_H)
 	      -e 's|@''GNULIB_OPENPTY''@|$(GNULIB_OPENPTY)|g' \
 	      -e 's|@''HAVE_UTIL_H''@|$(HAVE_UTIL_H)|g' \
 	      -e 's|@''HAVE_LIBUTIL_H''@|$(HAVE_LIBUTIL_H)|g' \
+	      -e 's|@''REPLACE_FORKPTY''@|$(REPLACE_FORKPTY)|g' \
+	      -e 's|@''REPLACE_OPENPTY''@|$(REPLACE_OPENPTY)|g' \
 	      -e '/definitions of _GL_FUNCDECL_RPL/r $(CXXDEFS_H)' \
 	      -e '/definition of _GL_WARN_ON_USE/r $(WARN_ON_USE_H)' \
 	      < $(srcdir)/pty.in.h; \
diff --git a/tests/test-openpty.c b/tests/test-openpty.c
index 255aeb0ddc..2af25b49cb 100644
--- a/tests/test-openpty.c
+++ b/tests/test-openpty.c
@@ -21,8 +21,8 @@
 #include <pty.h>
 
 #include "signature.h"
-SIGNATURE_CHECK (openpty, int, (int *, int *, char *, struct termios *,
-                                struct winsize *));
+SIGNATURE_CHECK (openpty, int, (int *, int *, char *, struct termios const *,
+                                struct winsize const *));
 
 #include <stdio.h>