[Bug bzip2/28904] libbzip2: ‘cost[3]’ may be used uninitialized in this function [-Wmaybe-uninitialized]
demerphq at gmail dot com
sourceware-bugzilla@sourceware.org
Wed Apr 20 01:57:12 GMT 2022
https://sourceware.org/bugzilla/show_bug.cgi?id=28904
--- Comment #3 from demerphq <demerphq at gmail dot com> ---
On Wed, 20 Apr 2022 at 00:23, mark at klomp dot org
<sourceware-bugzilla@sourceware.org> wrote:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=28904
>
> --- Comment #2 from Mark Wielaard <mark at klomp dot org> ---
> A different solution might be to use the constant BZ_N_GROUPS instead of the
> variable nGroups when resetting the arrays:
>
> diff --git a/compress.c b/compress.c
> index 5dfa002..2dc5dc1 100644
> --- a/compress.c
> +++ b/compress.c
> @@ -321,7 +321,7 @@ void sendMTFValues ( EState* s )
> ---*/
> for (iter = 0; iter < BZ_N_ITERS; iter++) {
>
> - for (t = 0; t < nGroups; t++) fave[t] = 0;
> + for (t = 0; t < BZ_N_GROUPS; t++) fave[t] = 0;
>
> for (t = 0; t < nGroups; t++)
> for (v = 0; v < alphaSize; v++)
> @@ -353,7 +353,7 @@ void sendMTFValues ( EState* s )
> Calculate the cost of this group as coded
> by each of the coding tables.
> --*/
> - for (t = 0; t < nGroups; t++) cost[t] = 0;
> + for (t = 0; t < BZ_N_GROUPS; t++) cost[t] = 0;
>
> if (nGroups == 6 && 50 == ge-gs+1) {
> /*--- fast track the common case ---*/
>
> Which might also help the compiler to simply zero the whole (6 element) arrays
> in one go (the common case), instead of having to check whether nGroups is
> smaller in this particular case.
I am fine with both of your proposals. I was wondering why you don't
use memset() instead of the explicit loop? From what I understand it
is faster.
Yves
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