45131: Make a function that redefines itself preserve its tracedness.

This makes it easy to apply local tracing ('functions -T') to autoloadable
functions that redefines themselves when first loaded.

ChangeLog

@@ -1,3 +1,8 @@
+2019-12-26  Daniel Shahaf  <danielsh@apache.org>
+
+	* 45131: Src/exec.c, Test/E02xtrace.ztst: Make a function that
+	redefines itself preserve its tracedness.
+
 2019-12-23  Daniel Shahaf  <danielsh@apache.org>
 
 	* unposted: Completion/Unix/Command/_stdbuf: Fix mismatch

Src/exec.c

@@ -5320,6 +5320,12 @@ execfuncdef(Estate state, Eprog redir_prog)
 		 */
 		removetrapnode(signum);
 	    }
+	    /* Is this function traced and redefining itself? */
+	    if (funcstack && funcstack->tp == FS_FUNC &&
+		    !strcmp(s, funcstack->name)) {
+		Shfunc old = ((Shfunc)shfunctab->getnode(shfunctab, s));
+		shf->node.flags |= old->node.flags & (PM_TAGGED|PM_TAGGED_LOCAL);
+	    }
 	    shfunctab->addnode(shfunctab, ztrdup(s), shf);
 	}
     }

Test/E02xtrace.ztst

@@ -146,3 +146,12 @@