Patch to handle empty sed expressions

[Matthew R. Dempsky]

Some packages (e.g., binutils 2.17) want to issue sed commands like

  s,^.*/,,;s,^,avr-,;;s/$//

but OpenBSD's sed doesn't handle empty expressions as in this.  The
patch below adds support for this.

(It also eliminates a useless null pointer check:  p is checked for
nullity when it is set a few lines above the hunk, and p is also
dereferenced later without null checks.)

Index: src/usr.bin/sed/compile.c
===================================================================
RCS file: /cvs/src/usr.bin/sed/compile.c,v
retrieving revision 1.22
diff -p -u -r1.22 compile.c
--- src/usr.bin/sed/compile.c   9 Oct 2006 00:23:56 -0000       1.22
+++ src/usr.bin/sed/compile.c   2 Jan 2007 04:28:29 -0000
@@ -161,8 +161,12 @@ compile_stream(struct s_command **link)
                }
 
 semicolon:     EATSPACE();
-               if (p && (*p == '#' || *p == '\0'))
+               if (*p == '#' || *p == '\0')
                        continue;
+               if (*p == ';') {
+                       p++;
+                       goto semicolon;
+               }
                *link = cmd = xmalloc(sizeof(struct s_command));
                link = &cmd->next;
                cmd->nonsel = cmd->inrange = 0;