On Mon, Feb 05, 2024 at 12:51:57PM +0100, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> > ---
> > libavfilter/signature_lookup.c | 21 ++++++++++-----------
> > 1 file changed, 10 insertions(+), 11 deletions(-)
> >
> > diff --git a/libavfilter/signature_lookup.c b/libavfilter/signature_lookup.c
> > index 86dd0c66754..52a97e1bc7e 100644
> > --- a/libavfilter/signature_lookup.c
> > +++ b/libavfilter/signature_lookup.c
> > @@ -37,6 +37,15 @@
> > #define STATUS_END_REACHED 1
> > #define STATUS_BEGIN_REACHED 2
> >
> > +static void sll_free(MatchingInfo **sll)
> > +{
> > + while (*sll) {
> > + MatchingInfo *tmp = *sll;
> > + *sll = (*sll)->next;
> > + av_free(tmp);
> > + }
>
> This does not clear the pointers at all. This does (and avoids
> indirections).
>
> static void sll_free(MatchingInfo **sllp)
> {
> MatchingInfo *sll = *sllp;
>
> *sllp = NULL;
> while (sll) {
> MatchingInfo *tmp = sll;
> sll = sll->next;
> av_free(tmp);
> }
> }
I tried it with code below, but your code is not different from mine in
behavior just more complex
output:
(nil) 0x560e8daad2c0 (nil)
vs.
(nil) 0x557ae6e472c0 (nil)
sll_free_n2() is simpler and will clear all, the reason i did not
propose it, is its recursive and can hit stack space limits in principle
sll_free_n3() and sll_free_n4() are other options that will clear all
but maybe every choice contains bugs, i didnt really test them with more than
one testcase
-----------
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define FFSWAP(type,a,b) do{type SWAP_tmp= b; b= a; a= SWAP_tmp;}while(0)
static void av_free(void *ptr)
{
free(ptr);
}
static void av_freep(void *arg)
{
void *val;
memcpy(&val, arg, sizeof(val));
memcpy(arg, &(void *){ NULL }, sizeof(val));
av_free(val);
}
typedef struct MatchingInfo {
struct MatchingInfo *next;
} MatchingInfo;
static void sll_free_n(MatchingInfo **sll)
{
while (*sll) {
MatchingInfo *tmp = *sll;
*sll = (*sll)->next;
av_free(tmp);
}
}
static void sll_free_n2(MatchingInfo **sll)
{
if (*sll)
sll_free_n(&(*sll)->next);
av_freep(sll);
}
static void sll_free_n3(MatchingInfo **sll)
{
while (*sll) {
MatchingInfo *tmp = *sll;
*sll = tmp->next;
tmp->next = NULL;
av_free(tmp);
}
}
static void sll_free_n4(MatchingInfo **sll)
{
MatchingInfo *tmp = NULL;
while (*sll) {
FFSWAP(MatchingInfo *, tmp, (*sll)->next);
av_freep(sll);
FFSWAP(MatchingInfo *, tmp, *sll);
}
}
static void sll_free_r(MatchingInfo **sllp)
{
MatchingInfo *sll = *sllp;
*sllp = NULL;
while (sll) {
MatchingInfo *tmp = sll;
sll = sll->next;
av_free(tmp);
}
}
main() {
MatchingInfo *mi, *m1, *m2;
m1 = mi = malloc(sizeof(MatchingInfo));
m2 = mi->next = malloc(sizeof(MatchingInfo));
m2->next= NULL;
sll_free_r(&mi);
printf("%p %p %p\n", mi, m1->next, m2->next);
}
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
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