code review 154540044: cmd/gc: emit code for extern = <N>

src/cmd/gc/gen.c

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 /*
  * portable half of code generator.
  * mainly statements and control flow.
  */
 
 #include <u.h>
@@ skipping 714 matching lines @@
 
         while(nr != N && nr->op == OCONVNOP)
                 nr = nr->left;
 
         if(nl == N || isblank(nl)) {
                 cgen_discard(nr);
                 return;
         }
 
         if(nr == N || iszero(nr)) {
-                // externals and heaps should already be clear
-                if(nr == N) {
-                        if(nl->class == PEXTERN)
-                                return;
-                        if(nl->class & PHEAP)
-                                return;
-                }
+                // heaps should already be clear
+                if(nr == N && (nl->class & PHEAP))
+                        return;
 
                 tl = nl->type;
                 if(tl == T)
                         return;
                 if(isfat(tl)) {
                         if(nl->op == ONAME)
                                 gvardef(nl);
                         clearfat(nl);
                         return;
                 }
@@ skipping 234 matching lines @@
 Node*
 temp(Type *t)
 {
         Node *n;
 ········
         n = nod(OXXX, N, N);
         tempname(n, t);
         n->sym->def->used = 1;
         return n->orig;
 }