linux-kernel - Re: [PATCH 16/16] fix handling of integer constant expressions

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Date:	Wed, 27 Jun 2007 14:18:23 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Neil Booth <neil@...kokuya.co.uk>
Cc:	Josh Triplett <josh@...edesktop.org>,
	Segher Boessenkool <segher@...nel.crashing.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-sparse@...r.kernel.org
Subject: Re: [PATCH 16/16] fix handling of integer constant expressions

On Wed, Jun 27, 2007 at 09:59:58PM +0900, Neil Booth wrote:
> Al Viro wrote:-
> 
> > If you want to test ICE recognition, right now only the following places
> > are checking for it:
> > 	* bitfield width
> > 	* __attribute__((aligned(<number>)))
> > 	* __attribute__((address_space(<number>)))
> > 	* [<index>] in designators within initializer list
> > 	* [<index> ... <index>] - ditto, gccism
> > 
> > That's it.  We can use it elsewhere too, but that's a separate bunch of
> > patches (trivial to do now).
> 
> Bah.  You don't escape that easily :)
> 
> extern int a;
> struct b { unsigned int b1:(1,2); };

Son of a...  expand_comma() cannibalizes the node, should restore ->flags
to 0 (same as other similar suckers).

> struct c { unsigned int c1: 1 ? 2: a++; };

Ditto for expand_conditional, but there we should preserve the original
->flags instead - might be non-zero and we ought to do that after
expanding the taken branch...

From: Al Viro <viro@...iv.linux.org.uk>
Date: Wed, 27 Jun 2007 09:10:54 -0400
Subject: [PATCH] fix the missed cannibalizing simplifications

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 expand.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/expand.c b/expand.c
index f945518..9a536d5 100644
--- a/expand.c
+++ b/expand.c
@@ -429,8 +429,10 @@ static int expand_comma(struct expression *expr)
 
 	cost = expand_expression(expr->left);
 	cost += expand_expression(expr->right);
-	if (expr->left->type == EXPR_VALUE || expr->left->type == EXPR_FVALUE)
+	if (expr->left->type == EXPR_VALUE || expr->left->type == EXPR_FVALUE) {
 		*expr = *expr->right;
+		expr->flags = 0;
+	}
 	return cost;
 }
 
@@ -488,12 +490,15 @@ static int expand_conditional(struct expression *expr)
 
 	cond_cost = expand_expression(cond);
 	if (cond->type == EXPR_VALUE) {
+		unsigned flags = expr->flags;
 		if (!cond->value)
 			true = false;
 		if (!true)
 			true = cond;
+		cost = expand_expression(*true);
 		*expr = *true;
-		return expand_expression(expr);
+		expr->flags = flags;
+		return cost;
 	}
 
 	cost = expand_expression(true);
-- 
1.5.0-rc2.GIT

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