Mercury Bugs - mercury
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0000537mercuryFeature Requestpublic2021-08-31 20:402021-08-31 20:40
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Summary0000537: unique file handles
DescriptionAt the moment, once you open a file and get a file handle, you can
(try to) perform operations using that handle even after the handle
is closed.

We could add a new module to the library, called maybe uio.m,
where an open of a file gives you a *unique* file handle. Every
operation then takes a di,uo pair of the relevant kind of unique
file handle ({in,out}put, {text,binary}, and gives you back the
same handle you gave it. The exception is the close operation,
which takes a di file handle. This way, mode analysis could guarantee
the absence of operations on closed files.

The implementation would be simple, using type casts to the existing
file handle types with foreign code, followed by a call to the
equivalent predicate in io.m.

We would need some mechanism to detect the duplication of these unique
file handles during forks and fork-like operations, but that shouldn't
be too hard.
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2021-08-31 20:40zsNew Issue