typedefs and alignment

typedefs and alignment

[Dan Carpenter]

I've found an issue handling typedefs and alignment.  In the appended 
code sparse things 'ptr' has to be aligned so the size of 'bar' is 1024.
I haven't looked at how to fix this at all, I thought I would ask the
experts for hints first.

regards,
dan carpenter

#include <stdio.h>

typedef struct aligned_struct {
	int a;
}  __attribute__ ((aligned(1024))) ali_t;

struct foo {
	int b;
	ali_t *ptr;
};

int mainx(void)
{
	struct foo bar;

	printf("%d\n", sizeof(bar));
	return 0;
}

Re: typedefs and alignment

[Christopher Li]

On Mon, Feb 8, 2010 at 2:35 AM, Dan Carpenter <error27@gmail.com> wrote:
> I've found an issue handling typedefs and alignment.  In the appended
> code sparse things 'ptr' has to be aligned so the size of 'bar' is 1024.
> I haven't looked at how to fix this at all, I thought I would ask the
> experts for hints first.

Hmm, there is a bug there.

For the simplified code:

typedef struct aligned_struct {
       int a;
}  __attribute__ ((aligned(1024))) ali_t;

ali_t *ppr;

running test-parsing will show:

.align 1024
struct aligned_struct [usertype] *[addressable] [toplevel] ppr

I am looking at it right now.

Chris



>
> regards,
> dan carpenter
>
> #include <stdio.h>
>
> typedef struct aligned_struct {
>        int a;
> }  __attribute__ ((aligned(1024))) ali_t;
>
> struct foo {
>        int b;
>        ali_t *ptr;
> };

It does look wrong. The easier way to expose it


>
> int mainx(void)
> {
>        struct foo bar;
>
>        printf("%d\n", sizeof(bar));
>        return 0;
> }
> --
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Re: typedefs and alignment

[Chris Li]

[-- Attachment #1: Type: text/plain, Size: 379 bytes --]

On Mon, Feb 8, 2010 at 2:35 AM, Dan Carpenter <error27@gmail.com> wrote:
> I've found an issue handling typedefs and alignment.  In the appended
> code sparse things 'ptr' has to be aligned so the size of 'bar' is 1024.
> I haven't looked at how to fix this at all, I thought I would ask the
> experts for hints first.

Can you try this one line patch?

Thanks

Chris

[-- Attachment #2: 0002-Pointer-don-t-inherent-the-alignment-from-base-type.patch --]
[-- Type: application/octet-stream, Size: 756 bytes --]

From 27af04c47164d6c6a49f64c568d24d99a902e449 Mon Sep 17 00:00:00 2001
From: Christopher Li <chrisl@heli.(none)>
Date: Wed, 10 Feb 2010 01:32:30 -0800
Subject: [PATCH 2/2] Pointer don't inherent the alignment from base type

Signed-off-by: Christopher Li <sparse@chrisli.org>
---
 parse.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/parse.c b/parse.c
index 66b8112..f81b19f 100644
--- a/parse.c
+++ b/parse.c
@@ -1698,6 +1698,7 @@ static struct token *pointer(struct token *token, struct decl_state *ctx)
 		ctx->ctype.base_type = ptr;
 		ctx->ctype.as = 0;
 		ctx->ctype.contexts = NULL;
+		ctx->ctype.alignment = 0;
 
 		token = handle_qualifiers(token->next, ctx);
 		ctx->ctype.base_type->endpos = token->pos;
-- 
1.6.2.5

Re: typedefs and alignment

[Dan Carpenter]

On Wed, Feb 10, 2010 at 01:46:39AM -0800, Chris Li wrote:
> On Mon, Feb 8, 2010 at 2:35 AM, Dan Carpenter <error27@gmail.com> wrote:
> > I've found an issue handling typedefs and alignment.  In the appended
> > code sparse things 'ptr' has to be aligned so the size of 'bar' is 1024.
> > I haven't looked at how to fix this at all, I thought I would ask the
> > experts for hints first.
> 
> Can you try this one line patch?
> 

Works great.  Thanks so much.

regards,
dan carpenter

> Thanks
> 
> Chris


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