Language clarification.
The existing rules for selector expressions imply
automatic dereferencing of pointers to struct fields.
They also implied automatic dereferencing of selectors
denoting methods. In almost all cases, such automatic
dereferencing does indeed take place for methods but the
reason is not the selector rules but the fact that method
sets include both methods with T and *T receivers; so for
a *T actual receiver, a method expecting a formal T
receiver, also accepts a *T (and the invocation or method
value expression is the reason for the auto-derefering).
However, the rules as stated so far implied that even in
case of a variable p of named pointer type P, a selector
expression p.f would always be shorthand for (*p).f. This
is true for field selectors f, but cannot be true for
method selectors since a named pointer type always has an
empty method set.
Named pointer types may never appear as anonymous field
types (and method receivers, for that matter), so this
only applies to variables declared of a named pointer
type. This is exceedingly rare and perhaps shouldn't be
permitted in the first place (but we cannot change that).
Amended the selector rules to make auto-deref of values
of named pointer types an exception to the general rules
and added corresponding examples with explanations.
Both gc and gccgo have a bug where they do auto-deref
pointers of named types in method selectors where they
should not:
See http://play.golang.org/p/c6VhjcIVdM , line 45.
Fixes#5769.
Fixes#8989.
LGTM=r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/168790043
People viewing this locally will not have a /s/ on their local godoc.
tip.golang.org doesn't have one either.
Also change all golang.org links to https, to avoid mixed content
warnings when viewing https://golang.org/.
Fixes#9028.
LGTM=bradfitz, r
R=r, bradfitz
CC=adg, golang-codereviews
https://golang.org/cl/168250043
Add a short introductory section saying what most Go
programmers really need to know, which is that you
shouldn't have to read this document to understand
the behavior of your program.
LGTM=bradfitz, adg, tracey.brendan, iant, rsc, dsymonds
R=golang-codereviews, bradfitz, tracey.brendan, adg, iant, rsc, dsymonds
CC=golang-codereviews
https://golang.org/cl/158500043
Not a language change.
This is simply documenting the status quo which permits
builtin function names to be parenthesized in calls; e.g.,
both
len(s)
and
(((len)))(s)
are accepted by all compilers and go/types.
Changed the grammar by merging the details of BuiltinCall
with ordinary Calls. Also renamed the Call production to
Arguments which more clearly identifies that part of the
grammar and also matches better with its counterpart on
the declaration side (Parameters).
The fact that the first argument can be a type (for builtins)
or cannot be a type (for regular function calls) is expressed
in the prose, no need to make the grammar more complicated.
Fixes#9001.
LGTM=iant, r, rsc
R=r, rsc, iant, ken, dave
CC=golang-codereviews
https://golang.org/cl/160570043
Move the release notes into an HTML file.
Start writing the text.
LGTM=rsc
R=golang-codereviews, bradfitz, kamil.kisiel, tracey.brendan, rsc
CC=golang-codereviews
https://golang.org/cl/161350043
Wrong article, one stylistic point that bothers someone (but not me).
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/156680043
The compatibility guideline needs to be clear about this even
though it means adding a clause that was not there from the
beginning. It has always been understood, so this isn't really
a change in policy, just in its expression.
LGTM=bradfitz, gri, rsc
R=golang-codereviews, bradfitz, gri, rsc
CC=golang-codereviews
https://golang.org/cl/162060043
Per suggestion from rsc as a result of the dicussion of
(abandoned) CL 153110044.
Fixes#7192.
LGTM=r, rsc, iant
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/163050043
This new text won't stop the whining but it might focus the whining a little more.
LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/146680044
Not a language change.
Several inaccuracies were fixed:
1) A variable declaration may declare more than just one
variable.
2) Variable initialization follows the rules of assignments,
including n:1 assignments. The existing wording implied a 1:1
or n:n rule and generally was somewhat unspecific.
3) The rules for variable declarations with no types and
untyped initialization expressions had minor holes (issue 8088).
4) Clarified the special cases of assignments of untyped values
(we don't just have untyped constants, but also untyped bools,
e.g. from comparisons). The new wording is more direct.
To that end, introduced the notion of an untyped constant's
"default type" so that the same concept doesn't have to be
repeatedly introduced.
Fixes#8088.
LGTM=iant, r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/142320043
The existing spec rules on package initialization were
contradictory: They specified that 1) dependent variables
are initialized in dependency order, and 2) independent
variables are initialized in declaration order. This 2nd
rule cannot be satisfied in general. For instance, for
var (
c = b + 2
a = 0
b = 1
)
because of its dependency on b, c must be initialized after b,
leading to the partial order b, c. Because a is independent of
b but is declared before b, we end up with the order: a, b, c.
But a is also independent of c and is declared after c, so the
order b, c, a should also be valid in contradiction to a, b, c.
The new rules are given in form of an algorithm which outlines
initialization order explicitly.
gccgo and go/types already follow these rules.
Fixes#8485.
LGTM=iant, r, rsc
R=r, rsc, iant, ken, gordon.klaus, adonovan
CC=golang-codereviews
https://golang.org/cl/142880043
The proposed text in the last CL had a comma that was missing from the submitted spec.
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/150720043
This CL adjusts code referring to src/pkg to refer to src.
Immediately after submitting this CL, I will submit
a change doing 'hg mv src/pkg/* src'.
That change will be too large to review with Rietveld
but will contain only the 'hg mv'.
This CL will break the build.
The followup 'hg mv' will fix it.
For more about the move, see golang.org/s/go14nopkg.
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/134570043
Preparation for fixing issue 5769 (method selectors
do not auto-dereference): The actual fix may require
some cleanups in all these sections, and syntactically,
method expressions and method values are selector
expressions. Moving them next to each other so that
it's easy to see the actual changes (next CL).
No content changes besides the section moves.
LGTM=iant, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/132300043
The file is used by assembly code to define symbols like NOSPLIT.
Having it hidden inside the cmd directory makes it hard to access
outside the standard repository.
Solution: As with a couple of other files used by cgo, copy the
file into the pkg directory and add a -I argument to the assembler
to access it. Thus one can write just
#include "textflag.h"
in .s files.
The names in runtime are not updated because in the boot sequence the
file has not been copied yet when runtime is built. All other .s files
in the repository are updated.
Changes to doc/asm.html, src/cmd/dist/build.c, and src/cmd/go/build.go
are hand-made. The rest are just the renaming done by a global
substitution. (Yay sam).
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/128050043
You talked me into it. This and other links should be updated
once the new import paths for the subrepos are established.
LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/124260043
Add a clause to the doc comment for the package and a
paragraph in the compatibility document explaining the
situation.
LGTM=bradfitz, adg, rsc
R=golang-codereviews, adg, bradfitz, minux, rsc
CC=golang-codereviews
https://golang.org/cl/129820043
Technically a language change, this cleanup is a completely
backward compatible change that brings the boolean results
of comma-ok expressions in line with the boolean results of
comparisons: they are now all untyped booleans.
The implementation effort should be minimal (less than a
handfull lines of code, depending how well factored the
implementation of comma-ok expressions is).
Fixes#8189.
LGTM=iant, r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/112320045
golang.org now serves HTTPS with a valid cert, so it's reasonable
that users should click through to the HTTPS versions of *.golang.org
and other known sites.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/112650043
I've found this very useful for generating
good test case lists for -short mode for
the disassemblers.
Fixes#7959.
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/98150043
This is a fully backward-compatible language change.
There are not a lot of cases in the std library, but
there are some. Arguably this makes the syntax a bit
more regular - any trailing index variable that is _
can be left away, and there's some analogy to type
switches where the temporary can be left away.
Implementation-wise the change should be trivial as
it can be done completely syntactically. For instance,
the respective change in go/parser is a dozen lines
(see https://golang.org/cl/112970044 ).
Fixes#6102.
LGTM=iant, r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/104680043
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
- A channel may be used between any number of goroutines,
not just two.
- Replace "passing a value" (which is not further defined)
by "sending and receiving a value".
- Made syntax production more symmetric.
- Talk about unbuffered channels before buffered channels.
- Clarify what the comma,ok receive values mean (issue 7785).
Not a language change.
Fixes#7785.
LGTM=rsc, r, iant
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/94030045
This is a clarification of what happens already.
Not a language change.
Fixes#7137.
LGTM=iant, r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/96000044
If the underlying type of a type T is a boolean, numeric,
or string type, then T is also a boolean, numeric, or
string type, respectively.
Not a language change.
Fixes#7551.
LGTM=iant, rsc, robert.hencke, r
R=r, rsc, iant, ken, robert.hencke
CC=golang-codereviews
https://golang.org/cl/100130044
Currently tip.golang.org leads to golang.org and
local godoc also leads to golang.org (when you don't have internet connectivity).
LGTM=crawshaw
R=golang-codereviews, crawshaw
CC=golang-codereviews
https://golang.org/cl/100200043
We will serve downloads from here until we work out a better plan.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/95980044
