Re: [gpsd-dev] [PATCH] Improved resilience in gps_shm_close() in case it is called after an unsuccessful gps_shm_open()

[Gary E. Miller]

Yo Robert!

Patch applied.  This fixes a nice hole.

I do find this mixing styles:

> +    if (PRIVATE(gpsdata) && PRIVATE(gpsdata)->shmseg != NULL)

I would be happy with, simple TRUE/FALSE:

    if (PRIVATE(gpsdata) && PRIVATE(gpsdata)->shmseg )

I think Eric prefers explicit comparisons, like this:

    if (PRIVATE(gpsdata) != NULL && PRIVATE(gpsdata)->shmseg != NULL)

It does smoke out type errors now and then.

And when I do that, I prefer the constant on the LEFT side.  I find
it allows the compiler to catch some non-obvious errors.

    if ( NULL != PRIVATE(gpsdata) && NULL != PRIVATE(gpsdata)->shmseg)

But that drives Eric batty, so avoid that for now.  :-)

On Mon, 1 Aug 2016 19:08:04 +0000
Robert Norris <address@hidden> wrote:

> Check that the structure exists before trying to use a component of
> it. ---
>  libgps_shm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libgps_shm.c b/libgps_shm.c
> index b256249..e0aa3ab 100644
> --- a/libgps_shm.c
> +++ b/libgps_shm.c
> @@ -153,7 +153,7 @@ int gps_shm_read(struct gps_data_t *gpsdata)
>  
>  void gps_shm_close(struct gps_data_t *gpsdata)
>  {
> -    if (PRIVATE(gpsdata)->shmseg != NULL)
> +    if (PRIVATE(gpsdata) && PRIVATE(gpsdata)->shmseg != NULL)
>       (void)shmdt((const void *)PRIVATE(gpsdata)->shmseg);
>  }
>  




RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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