expr.c (expr_expand_equ): Work around what I believe to be a GCC aliasing

bug (probably http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28778) by not
accepting NULL for eh, and giving it the static eh at the sole caller of
this function (yasm_expr__level_tree).  While I'm here, clean up the logic
a bit to avoid relying on ee.e NULL value.  This fix prevents crashes in
GCC 4.1.1 with -fstrict-aliasing (enabled by -O2).

Noticed by: Danny Reeves <danny_reeves@hotmail.com>

svn path=/trunk/yasm/; revision=1665

diff --git a/libyasm/expr.c b/libyasm/expr.c
index f5892989bb3b85ded9babeaaa66e24c346b0f6ab..9ebb098c2cfa0d6ece01002079a956279e2a66b5 100644 (file)
--- a/libyasm/expr.c
+++ b/libyasm/expr.c
@@ -809,50 +809,37 @@ static yasm_expr *
 expr_expand_equ(yasm_expr *e, yasm__exprhead *eh)
 {
     int i;
-    yasm__exprhead eh_local;
     yasm__exprentry ee;
 
-    if (!eh) {
-       eh = &eh_local;
-       SLIST_INIT(eh);
-    }
-
-    ee.e = NULL;
-
     /* traverse terms */
     for (i=0; i<e->numterms; i++) {
-       /* Expansion stage first: expand equ's. */
-       if (e->terms[i].type == YASM_EXPR_SYM) {
-           yasm__exprentry *np;
-           const yasm_expr *equ_expr =
-               yasm_symrec_get_equ(e->terms[i].data.sym);
-
-           if (equ_expr) {
-               /* Check for circular reference */
-               SLIST_FOREACH(np, eh, next) {
-                   if (np->e == equ_expr) {
-                       yasm_error_set(YASM_ERROR_TOO_COMPLEX,
-                                      N_("circular reference detected"));
-                       return e;
-                   }
-               }
+       const yasm_expr *equ_expr;
 
-               e->terms[i].type = YASM_EXPR_EXPR;
-               e->terms[i].data.expn = yasm_expr_copy(equ_expr);
+       /* Expand equ's. */
+       if (e->terms[i].type == YASM_EXPR_SYM &&
+           (equ_expr = yasm_symrec_get_equ(e->terms[i].data.sym))) {
+           yasm__exprentry *np;
 
-               ee.e = equ_expr;
-               SLIST_INSERT_HEAD(eh, &ee, next);
+           /* Check for circular reference */
+           SLIST_FOREACH(np, eh, next) {
+               if (np->e == equ_expr) {
+                   yasm_error_set(YASM_ERROR_TOO_COMPLEX,
+                                  N_("circular reference detected"));
+                   return e;
+               }
            }
-       }
 
-       /* Recurse */
-       if (e->terms[i].type == YASM_EXPR_EXPR)
-           e->terms[i].data.expn = expr_expand_equ(e->terms[i].data.expn, eh);
+           e->terms[i].type = YASM_EXPR_EXPR;
+           e->terms[i].data.expn = yasm_expr_copy(equ_expr);
 
-       if (ee.e) {
+           /* Remember we saw this equ and recurse */
+           ee.e = equ_expr;
+           SLIST_INSERT_HEAD(eh, &ee, next);
+           e->terms[i].data.expn = expr_expand_equ(e->terms[i].data.expn, eh);
            SLIST_REMOVE_HEAD(eh, next);
-           ee.e = NULL;
-       }
+       } else if (e->terms[i].type == YASM_EXPR_EXPR)
+           /* Recurse */
+           e->terms[i].data.expn = expr_expand_equ(e->terms[i].data.expn, eh);
     }
 
     return e;
@@ -907,10 +894,13 @@ yasm_expr__level_tree(yasm_expr *e, int fold_const, int simplify_ident,
                      yasm_expr_xform_func expr_xform_extra,
                      void *expr_xform_extra_data)
 {
+    yasm__exprhead eh;
+    SLIST_INIT(&eh);
+
     if (!e)
        return 0;
 
-    e = expr_expand_equ(e, NULL);
+    e = expr_expand_equ(e, &eh);
     e = expr_level_tree(e, fold_const, simplify_ident, simplify_reg_mul,
                        calc_bc_dist, expr_xform_extra, expr_xform_extra_data);