On Fri, Sep 17, 2021 at 02:58:09PM +0200, Tim Wiederhake wrote:
> This helps to bring down the frame size of virNWFilterRuleDefFixup, as it
> exceeds 8192 bytes when libvirt is build with sanitizers enabled, in debug
> mode, on clang.
>
> Signed-off-by: Tim Wiederhake <twiederh@xxxxxxxxxx>
> ---
> src/conf/nwfilter_conf.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/src/conf/nwfilter_conf.c b/src/conf/nwfilter_conf.c
> index a3109962af..62334edeec 100644
> --- a/src/conf/nwfilter_conf.c
> +++ b/src/conf/nwfilter_conf.c
> @@ -2189,23 +2189,23 @@ virNWFilterRuleValidate(virNWFilterRuleDef *rule)
> static void
> virNWFilterRuleDefFixup(virNWFilterRuleDef *rule)
> {
> + ethHdrDataDef *ethHdr;
> +
> #define COPY_NEG_SIGN(A, B) \
> (A).flags = ((A).flags & ~NWFILTER_ENTRY_ITEM_FLAG_IS_NEG) | \
> ((B).flags & NWFILTER_ENTRY_ITEM_FLAG_IS_NEG);
>
> switch (rule->prtclType) {
> case VIR_NWFILTER_RULE_PROTOCOL_MAC:
> - COPY_NEG_SIGN(rule->p.ethHdrFilter.ethHdr.dataSrcMACMask,
> - rule->p.ethHdrFilter.ethHdr.dataSrcMACAddr);
> - COPY_NEG_SIGN(rule->p.ethHdrFilter.ethHdr.dataDstMACMask,
> - rule->p.ethHdrFilter.ethHdr.dataDstMACAddr);
> + ethHdr = &rule->p.ethHdrFilter.ethHdr;
> + COPY_NEG_SIGN(ethHdr->dataSrcMACMask, ethHdr->dataSrcMACAddr);
> + COPY_NEG_SIGN(ethHdr->dataDstMACMask, ethHdr->dataDstMACAddr);
I don't get why this reduces stack size at all ?
COPY_NEG_SIGN is just doing a bitwise and + or + assignment
which doesn't require any intermediate variables.
Regards,
Daniel
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