Re: readline 6.3 violates POSIX by doing #undef setjmp

[Eric Blake]

On 01/23/2015 02:58 PM, Eric Blake wrote:
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/setjmp.html is
> clear:
> 
> "It is unspecified whether setjmp() is a macro or a function. If a macro
> definition is suppressed in order to access an actual function, or a
> program defines an external identifier with the name setjmp, the
> behavior is undefined."
> 
> But in readline's posixjmp.h wrapper file, you do:
> 
> #if defined (HAVE_POSIX_SIGSETJMP)
> #  define procenv_t     sigjmp_buf
> #  if !defined (__OPENNT)
> #    undef setjmp
> #    define setjmp(x)   sigsetjmp((x), 1)

You also define a setjmp_nosigs, but nothing in the readline sources
uses it.  For that matter, readline only has two instances of setjmp
clients, both which will never be reached when HAVE_POSIX_SIGSETJMP is
defined.

And why are you passing 0 to sigsetjmp in those two clients?  Don't you
generally want to preserve signal masks by passing a nonzero value,
rather than leave it unspecified whether they are preserved?

As for avoiding the undefined behavior, I think the patch is as simple as:

diff --git i/lib/readline/callback.c w/lib/readline/callback.c
index 6bb2c3e..56f43e7 100644
--- i/lib/readline/callback.c
+++ w/lib/readline/callback.c
@@ -1,6 +1,6 @@
 /* callback.c -- functions to use readline as an X `callback' mechanism. */

-/* Copyright (C) 1987-2009 Free Software Foundation, Inc.
+/* Copyright (C) 1987-2009, 2015 Free Software Foundation, Inc.

    This file is part of the GNU Readline Library (Readline), a library
    for reading lines of text with interactive input and history editing.
@@ -125,11 +125,7 @@ rl_callback_read_char ()
     }

   memcpy ((void *)olevel, (void *)_rl_top_level, sizeof (procenv_t));
-#if defined (HAVE_POSIX_SIGSETJMP)
   jcode = sigsetjmp (_rl_top_level, 0);
-#else
-  jcode = setjmp (_rl_top_level);
-#endif
   if (jcode)
     {
       (*rl_redisplay_function) ();
diff --git i/lib/readline/posixjmp.h w/lib/readline/posixjmp.h
index 98cf718..356828e 100644
--- i/lib/readline/posixjmp.h
+++ w/lib/readline/posixjmp.h
@@ -1,6 +1,6 @@
 /* posixjmp.h -- wrapper for setjmp.h with changes for POSIX systems. */

-/* Copyright (C) 1987,1991 Free Software Foundation, Inc.
+/* Copyright (C) 1987,1991,2015 Free Software Foundation, Inc.

    This file is part of GNU Bash, the Bourne Again SHell.

@@ -27,16 +27,11 @@

 #if defined (HAVE_POSIX_SIGSETJMP)
 #  define procenv_t    sigjmp_buf
-#  if !defined (__OPENNT)
-#    undef setjmp
-#    define setjmp(x)  sigsetjmp((x), 1)
-#    define setjmp_nosigs(x)   sigsetjmp((x), 0)
-#    undef longjmp
-#    define longjmp(x, n)      siglongjmp((x), (n))
-#  endif /* !__OPENNT */
 #else
 #  define procenv_t    jmp_buf
-#  define setjmp_nosigs        setjmp
+#  ifndef sigsetjmp
+#    define sigsetjmp(x, ignored) setjmp (x)
+#  endif
 #endif

 #endif /* _POSIXJMP_H_ */
diff --git i/lib/readline/readline.c w/lib/readline/readline.c
index abb29a0..f9ac97c 100644
--- i/lib/readline/readline.c
+++ w/lib/readline/readline.c
@@ -1,7 +1,7 @@
 /* readline.c -- a general facility for reading lines of input
    with emacs style editing and completion. */

-/* Copyright (C) 1987-2013 Free Software Foundation, Inc.
+/* Copyright (C) 1987-2013, 2015 Free Software Foundation, Inc.

    This file is part of the GNU Readline Library (Readline), a library
    for reading lines of text with interactive input and history
editing.
@@ -534,11 +534,7 @@ readline_internal_charloop ()
 #endif
       lk = _rl_last_command_was_kill;

-#if defined (HAVE_POSIX_SIGSETJMP)
       code = sigsetjmp (_rl_top_level, 0);
-#else
-      code = setjmp (_rl_top_level);
-#endif

       if (code)
        {


-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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