The runtime has historically held two dedicated values g (current goroutine)
and m (current thread) in 'extern register' slots (TLS on x86, real registers
backed by TLS on ARM).
This CL removes the extern register m; code now uses g->m.
On ARM, this frees up the register that formerly held m (R9).
This is important for NaCl, because NaCl ARM code cannot use R9 at all.
The Go 1 macrobenchmarks (those with per-op times >= 10 µs) are unaffected:
BenchmarkBinaryTree17 5491374955 5471024381 -0.37%
BenchmarkFannkuch11 4357101311 4275174828 -1.88%
BenchmarkGobDecode 11029957 11364184 +3.03%
BenchmarkGobEncode 6852205 6784822 -0.98%
BenchmarkGzip 650795967 650152275 -0.10%
BenchmarkGunzip 140962363 141041670 +0.06%
BenchmarkHTTPClientServer 71581 73081 +2.10%
BenchmarkJSONEncode 31928079 31913356 -0.05%
BenchmarkJSONDecode 117470065 113689916 -3.22%
BenchmarkMandelbrot200 6008923 5998712 -0.17%
BenchmarkGoParse 6310917 6327487 +0.26%
BenchmarkRegexpMatchMedium_1K 114568 114763 +0.17%
BenchmarkRegexpMatchHard_1K 168977 169244 +0.16%
BenchmarkRevcomp 935294971 914060918 -2.27%
BenchmarkTemplate 145917123 148186096 +1.55%
Minux previous reported larger variations, but these were caused by
run-to-run noise, not repeatable slowdowns.
Actual code changes by Minux.
I only did the docs and the benchmarking.
LGTM=dvyukov, iant, minux
R=minux, josharian, iant, dave, bradfitz, dvyukov
CC=golang-codereviews
https://golang.org/cl/109050043
This CL removes the special syntax for method receivers and
makes it just like other parameters. Instead, the crucial
receiver-specific rules (exactly one receiver, receiver type
must be of the form T or *T) are specified verbally instead
of syntactically.
This is a fully backward-compatible (and minor) syntax
relaxation. As a result, the following syntactic restrictions
(which are completely irrelevant) and which were only in place
for receivers are removed:
a) receiver types cannot be parenthesized
b) receiver parameter lists cannot have a trailing comma
The result of this CL is a simplication of the spec and the
implementation, with no impact on existing (or future) code.
Noteworthy:
- gc already permits a trailing comma at the end of a receiver
declaration:
func (recv T,) m() {}
This is technically a bug with the current spec; this CL will
legalize this notation.
- gccgo produces a misleading error when a trailing comma is used:
error: method has multiple receivers
(even though there's only one receiver)
- Compilers and type-checkers won't need to report errors anymore
if receiver types are parenthesized.
Fixes#4496.
LGTM=iant, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/101500044
This is a clone of 101370043, which I accidentally applied to the
release branch first.
No big deal, it needed to be applied there anyway.
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/108090043
The current wording is reversed in 2 places.
Not sure how it got 4 LGTMs (mine was there as well).
Update #6242.
LGTM=dan.kortschak, r, rsc
R=golang-codereviews, 0xjnml, dan.kortschak, r, rsc
CC=golang-codereviews
https://golang.org/cl/101980047
For incomplete struct S, C.T and C.struct_S were interchangeable in Go 1.2
and earlier, because all incomplete types were interchangeable
(even C.struct_S1 and C.struct_S2).
CL 76450043, which fixed issue 7409, made different incomplete types
different from Go's point of view, so that they were no longer completely
interchangeable.
However, imprecision about C.T and C.struct_S - really the same
underlying C type - is the one behavior enabled by the bug that
is most likely to be depended on by existing cgo code.
Explicitly allow it, to keep that code working.
Fixes#7786.
LGTM=iant, r
R=golang-codereviews, iant, r
CC=golang-codereviews
https://golang.org/cl/98580046
Also made it extra clear for goto statements (even though label scopes
are already limited to the function defining a label).
Fixes#8040.
LGTM=r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/99550043
The spec was unclear about whether blank methods should be
permitted in interface types. gccgo permits at most one, gc
crashes if there are more than one, go/types permits at most
one.
Discussion:
Since method sets of non-interface types never contain methods
with blank names (blank methods are never declared), it is impossible
to satisfy an interface with a blank method.
It is possible to declare variables of assignable interface types
(but not necessarily identical types) containing blank methods, and
assign those variables to each other, but the values of those
variables can only be nil.
There appear to be two "reasonable" alternatives:
1) Permit at most one blank method (since method names must be unique),
and consider it part of the interface. This is what appears to happen
now, with corner-case bugs. Such interfaces can never be implemented.
2) Permit arbitrary many blank methods but ignore them. This appears
to be closer to the handling of blank identifiers in declarations.
However, an interface type literal is not a declaration (it's a type
literal). Also, for struct types, blank identifiers are not ignored;
so the analogy with declarations is flawed.
Both these alternatives don't seem to add any benefit and are likely
(if only slightly) more complicated to explain and implement than
disallowing blank methods in interfaces altogether.
Fixes#6604.
LGTM=r, rsc, iant
R=r, rsc, ken, iant
CC=golang-codereviews
https://golang.org/cl/99410046
The key property here is what the bit pattern represents,
not what its type is. Storing 5 into a pointer is the problem.
Storing a uintptr that holds pointer bits back into a pointer
is not as much of a problem, and not what we are claiming
the runtime will detect.
Longer discussion at
https://groups.google.com/d/msg/golang-nuts/dIGISmr9hw0/0jO4ce85Eh0J
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/98370045
The spec did not specify the order in which
init() functions are called. Specify that
they are called in source order since we have
now also specified the initialization order
of independent variables.
While technically a language change, no
existing code could have relied on this,
so this should not break anything.
Per suggestion from rsc.
LGTM=r, iant
R=rsc, iant, r, ken
CC=golang-codereviews
https://golang.org/cl/98420046
- split description of package initialization and
program execution
- better grouping of concerns in section on package
initialization
- more explicit definition of what constitues a
dependency
- removed language about constant dependencies -
they are computed at compile-time and not
initialized at run-time
- clarified that independent variables are initialized
in declaration order (rather than reference order)
Note that the last clarification is what distinguishes
gc and gccgo at the moment: gc uses reference order
(i.e., order in which variables are referenced in
initialization expressions), while gccgo uses declaration
order for independent variables.
Not a language change. But adopting this CL will
clarify what constitutes a dependency.
Fixes#6703.
LGTM=adonovan, r, iant, rsc
R=r, rsc, iant, ken, adonovan
CC=golang-codereviews
https://golang.org/cl/99020043
The move from 4kB to 8kB in Go 1.2 was to eliminate many stack split hot spots.
The move back to 4kB was predicated on copying stacks eliminating
the potential for hot spots.
Unfortunately, the fact that stacks do not copy 100% of the time means
that hot spots can still happen under the right conditions, and the slowdown
is worse now than it was in Go 1.2. There is a real program in issue 8030 that
sees about a 30x slowdown: it has a reflect call near the top of the stack
which inhibits any stack copying on that segment.
Go back to 8kB until stack copying can be used 100% of the time.
Fixes#8030.
LGTM=khr, dave, iant
R=iant, khr, r, bradfitz, dave
CC=golang-codereviews
https://golang.org/cl/92540043
Make it a little clearer how they are used, in particular that
it is not enough just to return a nil pointer on error, but also
to return an error value explaining the problem.
Fixes#1963.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/97360045
- use previously defined terms (with links) throughout
- specify evaluation order more precisely (in particular,
the evaluation time of rhs expressions in receive cases
was not specified)
- added extra example case
Not a language change.
Description matches observed behavior of code compiled
with gc and gccgo.
Fixes#7669.
LGTM=iant, r, rsc
R=r, rsc, iant, ken, josharian
CC=golang-codereviews
https://golang.org/cl/91230043
This change requires using SWIG version 3.0 or later. Earlier
versions of SWIG do not generate the pragmas required to use
the external linker.
Fixes#7155.
Fixes#7156.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/97120046
