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From: Andrew Morton on 26 May 2010 20:00
On Tue, 25 May 2010 18:37:48 -0400
Prarit Bhargava <prarit(a)redhat.com> wrote:

> Fix checkstack error:
>
> lib/decompress_bunzip2.c: In function ___get_next_block___:
> lib/decompress_bunzip2.c:511: warning: the frame size of 1932 bytes is larger than 1024 bytes
>
> byteCount, symToByte, and mtfSymbol cannot be declared static or allocated
> dynamically so place them in the bunzip_data struct.
>
> Signed-off-by: Prarit Bhargava <prarit(a)redhat.com>
>
> diff --git a/lib/decompress_bunzip2.c b/lib/decompress_bunzip2.c
> index a4e971d..81c8bb1 100644
> --- a/lib/decompress_bunzip2.c
> +++ b/lib/decompress_bunzip2.c
> @@ -107,6 +107,8 @@ struct bunzip_data {
> unsigned char selectors[32768]; /* nSelectors = 15 bits */
> struct group_data groups[MAX_GROUPS]; /* Huffman coding tables */
> int io_error; /* non-zero if we have IO error */
> + int byteCount[256];
> + unsigned char symToByte[256], mtfSymbol[256];
> };
>
>
> @@ -158,14 +160,16 @@ static int INIT get_next_block(struct bunzip_data *bd)
> int *base = NULL;
> int *limit = NULL;
> int dbufCount, nextSym, dbufSize, groupCount, selector,
> - i, j, k, t, runPos, symCount, symTotal, nSelectors,
> - byteCount[256];
> - unsigned char uc, symToByte[256], mtfSymbol[256], *selectors;
> + i, j, k, t, runPos, symCount, symTotal, nSelectors, *byteCount;
> + unsigned char uc, *symToByte, *mtfSymbol, *selectors;
> unsigned int *dbuf, origPtr;
>
> dbuf = bd->dbuf;
> dbufSize = bd->dbufSize;
> selectors = bd->selectors;
> + byteCount = bd->byteCount;
> + symToByte = bd->symToByte;
> + mtfSymbol = bd->mtfSymbol;
>
> /* Read in header signature and CRC, then validate signature.
> (last block signature means CRC is for whole file, return now) */

hm, I'm not sure that checkstack warnings are very relevant in the
contexts where this code executes, but the change is clean enough and
squishing a warning is good.
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From: H. Peter Anvin on 26 May 2010 20:10
On 05/26/2010 04:55 PM, Andrew Morton wrote:
> hm, I'm not sure that checkstack warnings are very relevant in the
> contexts where this code executes, but the change is clean enough and
> squishing a warning is good.

This code may be used by squashfs or btrfs, at least in the future, and
in those contexts it's highly relevant indeed.

-hpa
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