shm_open doesn't work (fix maybe).

From: Tom Brusehaver (N-Sysdyne Corporation) (
Date: Tue Apr 24 2001 - 11:46:20 EST

I have been chasing all around trying to find out why
shm_open always returns ENOSYS. It is implemented
in glibc-2.2.2, and seems the 2.4.3 kernel knows about

It seems the file linux/mm/shmem.c has:
    #define SHMEM_MAGIC 0x01021994

And the glibc-2.2.2/sysdeps/unix/sysv/linux/linux_fsinfo.h has:
    #define SHMFS_SUPER_MAGIC 0x02011994

Well, which is correct?

Looking for (trouble?) the reason, I found a patch">

where there seems to be a typo, the remove line is correct:
   -#define SHM_FS_MAGIC 0x02011994

but the insert line has the 0201 reversed:
   +#define SHMEM_MAGIC 0x01021994

Has anyone else run into this? (It seems the documentation on shmfs
is sparse, so I don't think too many folks are even messing with it).

Initially I thought, hey simple, just fix the kernel source, and
everyone will be happy. But, then I thought, ooof! code I build
for someone without a patched kernel will surely break. So then
I thought simple I'll fix glibc and statically link. Of course, then
someone will fix this, and all my binaries will be broken.

Help! what is the "right" fix.

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This archive was generated by hypermail 2b29 : Mon Apr 30 2001 - 21:00:12 EST