In CS, if you interrupt an especially tight non-tail recursion, such
as
(let loop ()
(cons 1 (loop)))
then the "context" view of the continuation (as recorded in a
continuation mark set) can take space that is a multiple of the size
of the continuation itself. That's a particular problem if the
too-deep recursion triggers the memory limit in DrRacket, because
DrRacket will then need a multiple of its current heap space to report
"out of memory".
(Note: Just keeping the continuation itself is not a good option,
because that may retain other data referenced by the continuation.)
This commit reduces the heap space used to gather a continuation
context, relying in part on new Chez Scheme support, but mostly it
limits the context length to roughly the same maximum as in BC. The BC
limit is an implementation artifact, but it turns out to have good
properties; informaiton on more than 64k continuation frames is rarely
useful. The limit could be a parameter, but a large built-in limit
seems likely good enough.
(Another note: Adding a limit argument to
`continuation-mark-set->context` doesn't help enough, because it's too
late by that point; too much memory has been used to repersent the
information that's in the mark set.)
The commit also tightens tracking of continuations for memory
accounting, reducing the chance that a thread's large continuation
will be charged to the wrong custodian.
samth said "I don't think the Friendly Environment policy should be thought of as part of copyright issues, or applying only to people who contribute code. Is there a different phrasing that would accomplish what you want here?" I have rephrased the reference to the Friendly Environment Policy and moved it before the License section to avoid confusion with copyright issues.
- A part of contract-out's code generation for struct assumes that
there's no parent struct and uses the provided struct name for
everything. This causes duplicate definitions when there are duplicate
field names where one is in a child struct and another is
in a parent struct. This PR fixes the problem.
- Disallow multiple #:omit-constructor
- Deprecate super-id. This information is unnecessary since we can
extract it from static struct information already. Attempting to
check that super-id is well-formed is error-prone due to how
the super struct type could be contracted which shields us from
detecting that they are indeed the super type.
- Utilize static struct field name information, and provide
the information when exporting a struct.
This PR is largely based on #732.
Fixes: #3266, #3269, #3271, and #3272
This commit adds `prop:struct-field-info` which is implemented to provide
static information about field names. The property is attached to all
struct types generated by `define-struct`.
The commit also modifies kernstructs to have the property.
Finally, the commit switches `struct-copy` to use the static field name
information when it's available.
It remains to change `contract-out` and `match`'s `struct*` to
recognize/attach this new property, but this could be done
separately in the future.
This PR is largely based on racket/racket#732, though the approach is slightly
different.
Although building with the wrong offsets is good enough to compile
the compiler to compile itself correctly, a broken intermediate
compilation can create confusion.
An operation like `box-cas!` can fail spuriously on some platforms,
such as ARM processors. Mention that in the documentation.
The `box-cas!` and similar implementations could instead retry on
spurious failure, and that would avoid potential problems with code
tested on x86, where there's no spurious failure. In this case,
though, it seems better to stick with the existing behavior and
stay closer to the machine operation.
As the documentation says, `datum->syntax` should use
`datum-intern-literal`. That helps avoid syntax-object mutability, and
it increases sharing in compiled forms. The use of
`datum-intern-literal` got lost when the expander was rewritten in
Racket.
Relevant to #3245
The default package scope is determined by consulting the user-scope
configuration, then falling back to the installation-scope
configuration, then defaulting to user.
So, if you have a user-scope configuration of `default-scope`, it
doesn't matter what the configuration says in other scopes, which
means that the output of `raco pkg config` can be confusing. Extra
output in this commit is intended to make it less confusing.
Probably the original mistake here was allowing `default-scope` at a
scope-specific layer, instead of having it just as an installation
configuration (like `name`).
* Document liberal-defines? argument of generate-expand-context
* Add make-expression-transformer
* Ensure `block` expands in an expression context
Also refactors block to depend on racket/base and syntax/ modules rather
than private pre-base dependencies so it can use
`make-expression-transformer` and `generate-expand-context`.
* Ensure `local` expands in an expression context
* Add macro.rktl tests for block and local
