compiler/make_hlds_passes.m:
We used to add all modules imported by an ancestor of the current module
to the set of used modules. Once upon a time, this was meant to stop
the compiler generating misleading warnings about imports being unused
when the import wasn't even done by the current module. However, since
we introduced structured representations of import- and use_module
declarations and taught unused_imports.m to use them, that has not been
an issue. However, a bad side-effect remained, which was that if
a module A imported a module B but did not use it, or it imported
module B in its interface but did not use in its interface, then
any warning we could generate about that import being unused was
suppressed by any import of module B in any of module A's ancestors.
(The "shadowing" mentioned above.)
Fix the problem by adding modules imported by ancestors of the
current module NOT to the set of used modules, but to a new field
in the module_info.
compiler/hlds_module.m:
Add this new field. As it happens, it is not needed right now,
but it may be needed later.
Update some documentation.
Note an only-tangentially-related problem.
compiler/unused_imports.m:
Fix a bug that was hiding behind the shadowing, which was that whether
the text of the warning message we generated for an unused local import-
or use_module declaration could be affected by the presence of an
import- or use_module declaration in an ancestor module.
Improve debugging infrastructure.
Make a predicate name more descriptive.
NEWS:
Announce the bugfix.
compiler/add_pragma_tabling.m:
compiler/add_solver.m:
compiler/add_type.m:
compiler/parse_string_format.m:
compiler/recompilation.usage.m:
compiler/recompilation.used_file.m:
library/io.call_system.m:
library/io.text_read.m:
library/random.sfc32.m:
library/random.sfc64.m:
library/random.system_rng.m:
library/string.parse_runtime.m:
library/string.parse_util.m:
library/string.to_string.m:
library/thread.closeable_channel.m:
mdbcomp/feedback.automatic_parallelism.m:
Delete imports that the fixed compiler now generates unused import
warnings for.
In the Mercury standard library, every exported predicate or function
has (or at least *should* have) a comment that documents it, including
the meanings of its arguments. About 35-40% of these modules put `'s
(left and right quotes) around the names of the variable representing
those arguments. Some tried to do it consistently (though there were spots
with unquoted or half quoted names), while some did it only a few places.
This is inconsistent: we should either do it everywhere, or nowhere.
This diff makes it nowhere, because
- this is what the majority of the standard library modules do;
- this is what virtually all of the modules in the compiler, profiler,
deep_profiler etc directories do;
- typing all those quotes when adding new predicates in modules that
follow this convention is a pain in the ass; and because
- on many modern terminals, `' looks non-symmetrical and weird.
Likewise, the comment explaining a predicate often started with
% `predname(arguments)' returns ...
This diff deletes these quotes as well, since they add nothing useful.
This diff does leave in place quotes around code fragments, both terms
and goals, where this helps delineate the boundaries of that fragment.
library/thread.closeable_channel.m:
Rename the `empty' result of closeable_channel.try_take to
`would_block'.
tests/hard_coded/closeable_channel_test.exp:
tests/hard_coded/closeable_channel_test.m:
Update test case.
This is a plausible sequence of events leading to a failure in the
hard_coded/closeable_channel_test.m test case:
thread A thread B
-------- --------
close(Chan)
channel.take(Chan)
-> mvar.read(Head)
-> semaphore.wait(Full)
is_closed(Chan, IsClosed)
-> mvar.try_read(Hole)
-> semaphore.try_wait(Full)
Thread B tries to take the next item from the channel, during which time
it holds the Full semaphore of the mvar at the read end of the channel.
Thread A attempts to verify that the channel is really closed.
It tries to read from the mvar at the write end of the channel, which is
the same mvar as thread B is reading from (because the channel is empty).
Thread A cannot acquire the Full semaphore of the mvar as the semaphore
is being held by thread B, resulting in the call is_closed(Chan, IsClosed)
to return with IsClosed = no.
library/thread.closeable_channel.m:
Delete the is_closed predicate. It was of questionable utility
anyway.
tests/hard_coded/closeable_channel_test.m:
Delete call to is_closed in test case.
library/thread.closeable_channel.m
Add the new module. It omits two operations from thread.channel.m:
- untake, because it is deprecated
- duplicate, because I'm not sure what it's useful for in practice
library/MODULES_DOC:
library/library.m
library/thread.m:
NEWS:
Mention the new module.
