Re: [PATCH v1 4/5] perf mem: Support record for hybrid platform

[Jin, Yao]

Hi Jiri,

On 5/25/2021 3:39 PM, Jin, Yao wrote:
> Hi Jiri,
>
> > > >       rec_argv = calloc(rec_argc + 1, sizeof(char *));
> > > >       if (!rec_argv)
> > > >           return -1;
> > > > +    /*
> > > > +     * Save the allocated event name strings.
> > > > +     */
> > > > +    rec_tmp = calloc(rec_argc + 1, sizeof(char *));
> > > > +    if (!rec_tmp) {
> > > > +        free(rec_argv);
> > > > +        return -1;
> > > > +    }
> > >
> > > why not do strdup on all of them and always call free instead?
> > > that would get rid of the rec_tmp and tmp_nr
> >
> > That is also one method. Let me try it.
>
> If we do strdup on all of them, such as,
>
>      if (e->record)
>          rec_argv[i++] = strdup("-W");
>
>      rec_argv[i++] = strdup("-d");
>
>      if (mem->phys_addr)
>          rec_argv[i++] = strdup("--phys-data");
>      ....
>
> That looks too much strdup used here. So I choose to use a rec_tmp[] to record the allocated string 
> and free them before exit the function.
>
> Or we record the start index and end index in rec_argv[] for the allocated event string, use strdup 
> on them and call free before exit the function.

This method looks also not OK.

The rec_argv[] is changed in cmd_record() for some complex command lines.

For example,

./perf mem record -- ./memtest -R0d -b2000 -d64 -n100

Before cmd_record(), rec_argv[3] = "-e".
After cmd_record(), rec_argv[3] = "-d64"

Even we do strdup on all of rec_argv[], but the entries are probably changed in cmd_record(), so we 
can't free the entries at the end of __cmd_record().

Maybe we have to use the original way which just records the allocated event string to a temporary 
array and free the whole array at the end of __cmd_record().

What do you think?

Thanks
Jin Yao

> What do you think?
>
> Thanks
> Jin Yao