#10103: guile-2.2.3
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Reporter: bdubbs@… | Owner: bdubbs@…
Type: enhancement | Status: assigned
Priority: normal | Milestone: 8.2
Component: BOOK | Version: SVN
Severity: normal | Resolution:
Keywords: |
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Comment (by bdubbs@…):
Changes in 2.2.3 (since 2.2.2):
* New interfaces and functionality
** (web uri) module has better support for RFC 3986
The URI standard, RFC 3986, defines additional "relative-ref" and
"URI-reference" data types. Thanks to Daniel Hartwig, Guile's support
for these URI subtypes has been improved. See "Universal Resource
Identifiers" in the manual, for more.
** struct-ref/unboxed and struct-set!/unboxed
These procedures should be used when accessing struct fields with type
`u' (unboxed). See "Structure Basics" in the manual, for full details.
** Improved support for arrays with non-zero lower bounds
Thanks to work by Daniel Llorens, Guile no longer exhibits buggy
behavior in "sort" or "sort!" on arrays with non-zero lower dimension
bounds. Arrays with non-zero lower dimension bounds are now allowed for
array-slice-for-each, and truncated-print now supports bitvectors and
arrays with non-zero lower bounds. General arrays are now supported as
well for random:hollow-sphere!.
** Add uintptr_t and intptr_t to FFI types.
See "Foreign Types" in the manual for full details.
* Compiler improvements
** Improve speed of compiler backend for functions without loops
This is a marginal speed improvement, especially for code compiled with
optimization level "-O1" or below.
** Disable slot pre-coloring for optimization level "-O1" or below
This improves the speed of the compiler backend.
** Improve complexity of constant subexpression elimination pass
This is a large speed improvement when compiling large files with the
default "-O2" pass.
** CPS conversion avoids generating return arity adapters if possible
In Guile, the expression in (define a EXP) may return 1 or more values.
This value elision in "value" context is implicit earlier in the Guile
compiler, in Tree-IL, but is made explicit in the CPS middle-end
language by the addition of the equivalent of explicit call-with-values
continuations that ignore additional values. However in many cases we
can avoid generating these extra continuations if we know that EXP is
single-valued, as is the case for example for constants or variable
references or the like.
Although these "arity-adapting continuations" would be removed by dead
code elimination at optimization level "-O2" or above, they were still
being needlessly generated in the first place. Guile now avoids
generating them, speeding up not only the optimizer at -O2 but also the
entire compiler pipeline at -O1 or below, as well as improving the
residual code at -O1 or below.
** Using uri? as a predicate on relative-refs deprecated
If you don't care whether the URI is a relative-ref or not, use
uri-reference?. If you do, use uri-reference? and relative-ref?.
In the future uri? will return a true value only for URIs that specify
a scheme.
** Struct tail arrays deprecated
Guile's structures used to have a facility whereby each instance of a
vtable can contain a variable-length tail array of values. The length
of the tail array was stored in the structure. This facility was
originally intended to allow C code to expose raw C structures with
word-sized tail arrays to Scheme.
However, the tail array facility was confusing and doesn't work very
well. It was very rarely used, but it insinuates itself into all
invocations of make-struct. For this reason the clumsily-named
`make-struct/no-tail' procedure can actually be more elegant in actual
use, because it doesn't have a random `0' argument stuck in the middle.
Tail arrays also inhibit optimization by allowing instances to affect
their shapes. In the absence of tail arrays, all instances of a given
vtable have the same number and kinds of fields. This uniformity can be
exploited by the runtime and the optimizer. The presence of tail arrays
make some of these optimizations more difficult.
Finally, the tail array facility is ad-hoc and does not compose with the
rest of Guile. If a Guile user wants an array with user-specified
length, it's best to use a vector. It is more clear in the code, and
the standard optimization techniques will do a good job with it.
For all of these reasons, tail arrays are deprecated in Guile 2.2 and
will be removed from Guile 3.0. Likewise, make-struct /
scm_make_struct is deprecated in favor of make-struct/no-tail /
scm_make_struct_no_tail. Perhaps one day we will be able to reclaim
the make-struct name!
** Struct "self" slots deprecated
It used to be that you could make a structure vtable that had "self"
slots. Instances of that vtable would have those slots initialized to
the instance itself. This can be useful in C code where you might have
a pointer to the data array, and want to get the `SCM' handle for the
structure. However this was a little used complication without any use
in Scheme code. To replace it, just use "p" slots and initialize the
slot values manually on initialization.
** Struct fields with opaque ("o") protection deprecated
Struct fields are declared with a "protection", meaning read-only ('r'),
read-write ('w'), or opaque ('o'). There is also "hidden" ('h') which
is read-write but which isn't initialized by arguments passed to
make-struct/no-tail, but that's a detail. Opaque struct fields were
used to allocate storage in a struct that could only be accessed by C.
This facility was very rarely used (unused in Guile itself) but now that
we are implementing more and more in Scheme, it is completely useless.
To enforce permissions on struct fields, instead layer on an abstraction
at a higher level, in the same way that immutable record fields are
simply those which don't have an accessor.
** Using struct-ref and struct-set! on unboxed fields is deprecated
Use the new struct-ref/unboxed and struct-set!/unboxed instead.
* Bug fixes
** guile.m4 now checks for Guile 2.2 by default
Before, it was still preferring Guile 2.0. It now also supports the
Guile 3.0 prereleases.
** Fix setting breakpoints from the REPL
** Allow GDB support to be used with GDB linked against Guile 2.0.
** Fix deadlock in `readdir' on error.
** Fix crash on ia64 during thread switches.
** Fix bug inferring range of `logand' computations with negative numbers
** Fix bug when issuing HTTP requests through proxies.
** Refactor weak hash table implementation to be more robust
Guile 2.2's weak hash table implementation had three big problems. The
first was a bug causing these tables to leak memory when they would be
resized. The second was that the implementation was designed so that
tables should be visited by the mark phase of the garbage collector in
one big piece. This could cause the garbage collector to see too many
newly marked objects at once, causing inefficies in garbage collection.
Finally, the way in which lost weak references were ultimately removed
from weak tables caused a race between the finalizer threads and the
mutator threads, leading to unbounded excess space retention in
pathological cases. All of this problems have been fixed.
** Allow garbage collection of revealed file ports
Guile can mark a file port as "revealed" if Scheme has been given access
to the file descriptor. In that case, the file descriptor will not be
closed when the port is garbage-collected. However we had a bug that
for revealed ports prevented the port from ever being garbage-collected,
leading to memory leaks of Guile's internal port buffers. This is now
fixed.
** Fix put-bytevector, unget-bytevector with start == bytevector length
** Enable GNU Readline 7.0's support for "bracketed paste".
Before, when pasting an expression that contained TAB characters into
Guile's REPL with GNU Readline support enabled, the pasted TAB
characters would trigger autocompletion in Readline. This was never
what you wanted. Guile now sets the new "bracketed-paste" option in GNU
Readline 7.0 to on by default, making readline treat pastes into the
terminal as atomic units without control characters. See "Readline
Options" in the manual for full details.
** Fix time-monotonic from SRFI-19; broken in 2.2.1.
--
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