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cc1: Detect decay'ed expressions in sizeof()

The current logic to avoid decay expressions used in sizeof
is too complex. It is better to just decay them and detect
the situation later and get the correct node and not the
decay'ed one.

--- a/src/cmd/cc/cc1/cc1.h

+++ b/src/cmd/cc/cc1/cc1.h

@@ -114,7 +114,8 @@

 enum {

 	NLVAL   = 1 << 0,

 	NCONST  = 1 << 1,

-	NEFFECT = 1 << 2

+	NEFFECT = 1 << 2,

+	NDECAY  = 1 << 3,

 };

 /* lexer mode, compiler or preprocessor directive */

--- a/src/cmd/cc/cc1/expr.c

+++ b/src/cmd/cc/cc1/expr.c

@@ -211,6 +211,8 @@

 	new = node(OADDR, mktype(tp, PTR, 0, NULL), np, NULL);

 	if (np->sym && np->sym->flags & (SGLOBAL|SLOCAL|SPRIVATE))

 		new->flags |= NCONST;

+	new->flags |= NDECAY;

+

 	return new;

 }

@@ -733,10 +735,16 @@

 static Type *

 typeof(Node *np)

 {

+	Node *new;

 	Type *tp;

 	if (np == NULL)

 		unexpected();

+	if ((np->flags & NDECAY) != 0) {

+		new = np->left;

+		free(np);

+		np = new;

+	}

 	tp = np->type;

 	freetree(np);

 	return tp;