While `#:in-original-place? #t` provides one way to serialize
foreign calls, it acts as a single lock and requires expensive
context switches. Using an explicit lock can be more efficient
for serializing calls across different places.
For example, running "plot.scrbl" takes 70 seconds on my machine
in the original place and using `#:lock-name` in any place,
while it took 162 seconds in a non-main place with Cairo+Pango
serialization via `#:in-original-place? #t`.
Internally, the named lock combines compare-and-swap with a
place channel. That strategy gives good performance in the case
of no contention, and it cooperates properly with the Racket
scheduler where there is contention.
The new variants pass a "self" argument to the wrapper procedure in
the same way that `{impersonate,chaperone}-struct` provides a "self"
argument to redirection procedures.
When calling a wrapper procedure for a field accessor or mutator,
provide the structure that was originally passed to the accessor or
mutator, instead of the value that was wrapped to create an
impersonator.
This is a backward-incompatible change, but I can't find any uses of
that initial argument to the wrapper procedure. Also, a wrapper can
capture the original value in its closure, while passing "self" allows
wrappers that are sensitive to overridden impersonator properties.
As suggested by Jan Dvořák.
The event created by `replace-evt` is a kind of event-gated
version of `guard-evt`. In particular,
(guard-evt thunk)
could be expressed as
(replace-evt always-evt (lambda (_) (thunk)))
Use `replace-evt` as a shortcut for the case when you want to
synchronize on either A or C, but you need to wait for B to get C.
You could wait on A+B and then, if B is selected, wait on A+C;
wrapping B with `replace-evt` to generate C is a kind of shortcut that
is eaiser to write and avoids tear-down and re-setup of A.
The `replace-evt` constructor is more than a shortcut in the sense
that it builds the pattern A+B->A+C into `sync`, which enables
abstractions that need a B->C transition. So, `replace-evt` adds
expressiveness, but (perhap reassuringly) it does not add any new
rendezvous capability.
Naturally, the procedure given to `replace-evt` can produce
another `replace-evt`, and the event argument to
`replace-evt` could also be a `replace-evt`.
Report packages that have no dependency declarations as "warnings"
(to stdout instead of stderr).
Report specific information when a dependency is discoeverd missing,
insteda of reporting it only in verbose mode.
The new `--no-pkg-deps' or `-K' flag skips the check.
If a module in package X refers to a module in package Y, check that
package X declares a dependency on Y. Note that package X must
specifically depend on Y --- not another package that at the moment
happens to declare a dependency on Y.
A new "base" package represents the content of the core (so that, if
the core shrinks, a new "base2" can represent the smaller core).
Most every package now needs a dependency on "base".
Sometimes, it makes sense for X to access Y when X declares a
dependency on Z, because Z promises to always depend on Y. For
example, the "gui" package is defined to combne "gui-lib" and
"gui-doc", so it's appropriate to use the modules of "gui-lib" when
depending on "gui". A package's "info.rkt" can therefore define
`implies' as a subset of the dependencies listed in `deps', which
means that depending on the package implies a dependency on the listed
packages. (It's even possible for packages to mutually imply each
other, which is why the dependency checking code ends up with a
union-find.)
Dependency checking distinguishes between run-time dependencies and
build-time dependencies: anything listed in a ".dep" file is a build
dependency, at least. To imply a run-time dependency, a reference must
appear in a bytecode file's imports, and not in a subdirectory or
submodule that would be pruned for a binary package.
The `--fix-pkg-deps' flag attempts to automatically fix package
dependency declarations (i.e., modify a package's "info.rkt" file)
based on inferred dependencies.
