I was curious why the MIT-SHM extension works, even with these noop
xf86shm*() entry points. The implementation of MIT-SHM:
xc/programs/Xserver/Xext/shm.c
Makes system calls directly, rather than going through the libc_wrapper.
- Andy Ritger
> Hi all, I have a few questions about the libc wrapper layer on FreeBSD,
> and its implementation of xf86shmat() and friends. On FreeBSD, XFree86's
> libc wrapper is:
>
> xc/programs/Xserver/hw/xfree86/os-support/bsd/libc_wrapper.c
>
> which is a symlink to:
>
> xc/programs/Xserver/hw/xfree86/os-support/shared/libc_wrapper.c
>
> There are two implementations of xf86shmget(), xf86shmat(),
> xf86shmctl(), and xf86shmdt() in libc_wrapper.c:
>
> - an implementation that just calls into the C library via shmget(),
> shmat(), shmdt() and shmctl(); this implementation is protected by
> "#ifdef HAVE_SYSV_IPC"
>
> - an implementation that is used when HAVE_SYSV_IPC is not
> defined; in this case, the four functions each just return -1.
>
> It seems that HAVE_SYSV_IPC is not defined by default. Is there a more
> correct way to enable it, rather than just adding "-DHAVE_SYSV_IPC" to
> the DefaultCCOptions in my host.def?
>
> When I do define HAVE_SYSV_IPC, then I hit a problem with the
> implementation of xf86shmat():
>
> char *
> xf86shmat(int id, char *addr, int xf86shmflg)
> {
> int shmflg = 0;
>
> if (xf86shmflg & XF86SHM_RDONLY) shmflg |= SHM_RDONLY;
> if (xf86shmflg & XF86SHM_RND) shmflg |= SHM_RND;
> if (xf86shmflg & XF86SHM_REMAP) shmflg |= SHM_REMAP;
>
> return shmat(id,addr,shmflg);
> }
>
> complaining that SHM_REMAP isn't defined. Grepping in /usr/include/,
> I couldn't find SHM_REMAP. Does anyone know if this doesn't exist on
> FreeBSD?
>
> I'm using FreeBSD-4.5 (haven't tried any of this on -CURRENT, yet).
>
> I'm a little confused how XFree86 could use shared memory with the
> current CVS code. Does anyone know anything about this?
>
>Thanks,
>- Andy Ritger
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