Re: (ITS#8976) LMDB > use posix_madvise(3) instead of madvise(3) for SmartOS

[matthieu.guegan@smile-suisse.com]

On Fri, Feb 15, 2019 at 4:33 PM Howard Chu <hyc@symas.com> wrote:
>
> Matthieu GUEGAN wrote:
> > On Fri, Feb 15, 2019 at 3:56 PM Howard Chu <hyc@symas.com> wrote:
> >>
> >> mguegan@virtua.ch wrote:
> >>> Full_Name: Matthieu Guegan
> >>> Version: current
> >>> OS: SmartOS
> >>> URL:
> >>> Submission from: (NULL) (109.190.148.77)
> >>>
> >>>
> >>> Hi,
> >>>
> >>> In order to compile knot[1] on SmartOS, I have done a series of little patches.
> >>> One of them is linked to the LMDB project, which redirects me here.
> >>>
> >>> The idea is to tell SmartOS (and I think the SunOS family) to make use of
> >>> posix_madvise(3), instead of madvise(3) as implementation on this OS[2] is
> >>> different than, for example, the Linux[3] one.
> >>>
> >>> So, I kindly ask you to take a look at the merge request of the knot project[4],
> >>> in particular the `src/contrib/lmdb/mdb.c` patch (that's just a ifdef
> >>> modification) : would it be possible to apply this patch directly in this
> >>> repository ?
> >>
> >> I see no functional difference between your references [2] and [3].
> >> What is the benefit of this patch?
> >
> > Well, the Solaris/SunOS's madvise(3) is defined with an old `caddr_t`
> > type whereas Linux (and *BSD OSes too) use a more modern approach with
> > `void *`.
> > On the `knot` project, which embed the lmdb part of openldap,
> > compilation failed when using madvise(3) on SmartOS, so I did a
> > replacement with posix_madvise(3) which uses the `void *` argument
> > too.
> > I don't know what's the best way to handle this case, that's why I ask here.
>
> A caddr_t is just a typedef of "char *". It should always be legal to
> pass a void * to such a parameter. What is your compile error message?
>

```
contrib/lmdb/mdb.c: In function 'mdb_env_map':
contrib/lmdb/mdb.c:3998:3: error: implicit declaration of function
'madvise'; did you mean 'raise'?
[-Werror=implicit-function-declaration]
   madvise(env->me_map, env->me_mapsize, MADV_RANDOM);
   ^~~~~~~
   raise
```