"enable name" when name is not a shell builtin attempts to load it from a shared object

builtins/enable.def

@@ -1,7 +1,7 @@
 This file is enable.def, from which is created enable.c.
 It implements the builtin "enable" in Bash.
 
-Copyright (C) 1987-2020 Free Software Foundation, Inc. 
+Copyright (C) 1987-2021 Free Software Foundation, Inc. 
 
 This file is part of GNU Bash, the Bourne Again SHell.
 
@@ -75,6 +75,7 @@ $END
 #define ENABLED  1
 #define DISABLED 2
 #define SPECIAL  4
+#define SILENT	 8	/* affects dyn_load_builtin behavior */
 
 #define AFLAG	0x01
 #define DFLAG	0x02
@@ -110,6 +111,7 @@ enable_builtin (list)
 {
   int result, flags;
   int opt, filter;
+  WORD_LIST *next;
 #if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
   char *filename;
 #endif
@@ -188,6 +190,8 @@ enable_builtin (list)
 	filter |= SPECIAL;
 
       result = dyn_load_builtin (list, filter, filename);
+      if (result != EXECUTION_SUCCESS)
+	result = EXECUTION_FAILURE;	/* normalize return value */
 #if defined (PROGRAMMABLE_COMPLETION)
       set_itemlist_dirty (&it_builtins);
 #endif
@@ -213,13 +217,37 @@ enable_builtin (list)
       while (list)
 	{
 	  opt = enable_shell_command (list->word->word, flags & NFLAG);
+	  next = list->next;
 
-	  if (opt == EXECUTION_FAILURE)
+#if defined (HAVE_DLOPEN) && defined (HAVE_DLSYM)
+	  /* If we try to enable a non-existent builtin, and we have dynamic
+	     loading, try the equivalent of `enable -f name name'. */
+	  if (opt == EX_NOTFOUND)
+	    {
+	      int dflags, r;
+	      
+	      dflags = ENABLED|SILENT|((flags & SFLAG) ? SPECIAL : 0);
+
+	      list->next = 0;
+	      r = dyn_load_builtin (list, dflags, list->word->word);
+	      list->next = next;
+	      if (r == EXECUTION_SUCCESS)
+		opt = r;
+#if defined (PROGRAMMABLE_COMPLETION)
+	      set_itemlist_dirty (&it_builtins);
+#endif
+	    }
+#endif
+
+	  if (opt == EX_NOTFOUND)
 	    {
 	      sh_notbuiltin (list->word->word);
 	      result = EXECUTION_FAILURE;
 	    }
-	  list = list->next;
+	  else if (opt != EXECUTION_SUCCESS)
+	    result = EXECUTION_FAILURE;
+
+	  list = next;
 	}
     }
   return (result);
@@ -261,7 +289,7 @@ enable_shell_command (name, disable_p)
 
   b = builtin_address_internal (name, 1);
   if (b == 0)
-    return (EXECUTION_FAILURE);
+    return (EX_NOTFOUND);
 
   if (disable_p)
     b->flags &= ~BUILTIN_ENABLED;
@@ -340,11 +368,16 @@ dyn_load_builtin (list, flags, filename)
 
   if (handle == 0)
     {
-      name = printable_filename (filename, 0);
-      builtin_error (_("cannot open shared object %s: %s"), name, dlerror ());
-      if (name != filename)
-	free (name);
-      return (EXECUTION_FAILURE);
+      /* If we've been told to be quiet, don't complain about not finding the
+	 specified shared object. */
+      if ((flags & SILENT) == 0)
+	{
+	  name = printable_filename (filename, 0);
+	  builtin_error (_("cannot open shared object %s: %s"), name, dlerror ());
+	  if (name != filename)
+	    free (name);
+	}
+      return (EX_NOTFOUND);
     }
 
   for (new = 0, l = list; l; l = l->next, new++)
@@ -370,7 +403,7 @@ dyn_load_builtin (list, flags, filename)
 	{
 	  name = printable_filename (filename, 0);
 	  builtin_error (_("cannot find %s in shared object %s: %s"),
-			  struct_name, name, dlerror ());
+			    struct_name, name, dlerror ());
 	  if (name != filename)
 	    free (name);
 	  free (struct_name);

doc/bash.1

@@ -5,12 +5,12 @@
 .\"	Case Western Reserve University
 .\"	chet.ramey@case.edu
 .\"
-.\"	Last Change: Wed Jun 16 09:50:34 EDT 2021
+.\"	Last Change: Fri Jul 30 15:05:43 EDT 2021
 .\"
 .\" bash_builtins, strip all but Built-Ins section
 .if \n(zZ=1 .ig zZ
 .if \n(zY=1 .ig zY
-.TH BASH 1 "2021 June 16" "GNU Bash 5.1"
+.TH BASH 1 "2021 July 30" "GNU Bash 5.1"
 .\"
 .\" There's some problem with having a `@'
 .\" in a tagged paragraph with the BSD man macros.
@@ -8451,6 +8451,11 @@ If \fB\-a\fP is supplied, the list printed includes all builtins, with an
 indication of whether or not each is enabled.
 If \fB\-s\fP is supplied, the output is restricted to the POSIX
 \fIspecial\fP builtins.
+If no options are supplied and a \fIname\fP is not a shell builtin,
+\fBenable\fP will attempt to load \fIname\fP from a shared object named
+\fIname\fP, as if the command were
+.if t \f(CWenable \-f\fP \fIname name\fP .
+.if n ``enable -f \fIname name\fP .
 The return value is 0 unless a
 .I name
 is not a shell builtin or there is an error loading a new builtin

doc/bashref.texi

@@ -4532,6 +4532,11 @@ The @option{-s} option restricts @code{enable} to the @sc{posix} special
 builtins.  If @option{-s} is used with @option{-f}, the new builtin becomes
 a special builtin (@pxref{Special Builtins}).
 
+If no options are supplied and a @var{name} is not a shell builtin,
+@code{enable} will attempt to load @var{name} from a shared object named
+@var{name}, as if the command were
+@samp{enable -f @var{name} @var{name}}.
+
 The return status is zero unless a @var{name} is not a shell builtin
 or there is an error loading a new builtin from a shared object.
 

doc/version.texi

@@ -2,10 +2,10 @@
 Copyright (C) 1988-2021 Free Software Foundation, Inc.
 @end ignore
 
-@set LASTCHANGE Wed Jun 16 09:50:57 EDT 2021
+@set LASTCHANGE Fri Jul 30 15:04:53 EDT 2021
 
 @set EDITION 5.1
 @set VERSION 5.1
 
-@set UPDATED 16 June 2021
-@set UPDATED-MONTH June 2021
+@set UPDATED 30 July 2021
+@set UPDATED-MONTH July 2021

examples/loadables/sleep.c

@@ -74,12 +74,19 @@ WORD_LIST	*list;
     	r = uconvert(list->word->word, &sec, &usec, &ep);
 	/* Maybe postprocess conversion failures here based on EP */
     		
-    	if (r) {
+	if (r) {
 		fsleep(sec, usec);
 		QUIT;
 		return(EXECUTION_SUCCESS);
-    	}
-
+	}
+	/*
+	 * A heuristic: if the conversion failed, but the argument appears to
+	 * contain a GNU-like interval specifier (e.g. "1m30s"), return the
+	 * right exit code to tell execute_builtin to try and execute a disk
+	 * command instead.
+	 */
+	if (strpbrk (list->word->word, "dhms"))
+		return(EX_DISKFALLBACK);
 	builtin_error("%s: bad sleep interval", list->word->word);
 	return (EXECUTION_FAILURE);
 }

execute_cmd.c

@@ -4740,7 +4740,10 @@ run_builtin:
 		      executing_builtin = old_builtin;
 		      executing_command_builtin = old_command_builtin;
 		      builtin = 0;
-		      /* XXX - redirections will have to be performed again */
+
+		      /* The redirections have already been `undone', so this
+			 will have to do them again. But piping is forever. */
+		      pipe_in = pipe_out = -1;
 		      goto execute_from_filesystem;
 		    }
 		  result = builtin_status (result);

tests/RUN-ONE-TEST

@@ -1,4 +1,4 @@
-BUILD_DIR=/usr/local/build/bash/bash-current
+BUILD_DIR=/usr/local/build/chet/bash/bash-current
 THIS_SH=$BUILD_DIR/bash
 PATH=$PATH:$BUILD_DIR