this.  The SUS text is a bit weaselly ("the application must ensure
correct synchronization") but the HPUX mmap man page, among others,
lays it on the line:

It is also unspecified whether write references to a memory region
mapped with MAP_SHARED are visible to processes reading the file and
whether writes to a file are visible to processes that have mapped the
modified portion of that file, except for the effect of msync().

It might work on particular OSes but I think depending on such behavior
would be folly...

Agreed. Only OSes with a coherent file system buffer cache should ever use mmap(2). In order for this to work on HPUX, msync(2) would need to be used. -sc

Sean Chittenden

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