qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-22 03:34:40 -07:00
Code Releases Activity

doc/go1.1.html: document the surrogate and BOM changes

Browse Source 
R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7853048
This commit is contained in:
Rob Pike 2013-03-18 22:50:32 -07:00
parent 646e54106d
commit b89a2bcf01
1 changed files with 53 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
doc/go1.1.html
View File

@ -34,13 +34,14 @@ In Go 1.1, an integer division by constant zero is not a legal program, so it is
<h2 id="impl">Changes to the implementations and tools</h2>
<li>TODO: more</li>
<li>TODO: unicode: surrogate halves in compiler, libraries, runtime</li>
<p>
TODO: more
</p>
<h3 id="gc-flag">Command-line flag parsing</h3>
<p>
In the gc toolchain, the compilers and linkers now use the
In the gc tool chain, the compilers and linkers now use the
same command-line flag parsing rules as the Go flag package, a departure
from the traditional Unix flag parsing. This may affect scripts that invoke
the tool directly.
@ -82,6 +83,52 @@ would instead say:
i := int(int32(x))
</pre>
<h3 id="unicode_surrogates">Unicode</h3>
<p>
To make it possible to represent code points greater than 65535 in UTF-16,
Unicode defines <em>surrogate halves</em>,
a range of code points to be used only in the assembly of large values, and only in UTF-16.
The code points in that surrogate range are illegal for any other purpose.
In Go 1.1, this constraint is honored by the compiler, libraries, and run-time:
a surrogate half is illegal as a rune value, when encoded as UTF-8, or when
encoded in isolation as UTF-16.
When encountered, for example in converting from a rune to UTF-8, it is
treated as an encoding error and will yield the replacement rune,
<a href="/pkg/unicode/utf8/#RuneError"><code>utf8.RuneError</code></a>,
U+FFFD.
</p>
<p>
This program,
</p>
<pre>
import "fmt"
func main() {
fmt.Printf("%+q\n", string(0xD800))
}
</pre>
<p>
printed <code>"\ud800"</code> in Go 1.0, but prints <code>"\ufffd"</code> in Go 1.1.
</p>
<p>
The Unicode byte order marks U+FFFE and U+FEFF, encoded in UTF-8, are now permitted as the first
character of a Go source file.
Even though their appearance in the byte-order-free UTF-8 encoding is clearly unnecessary,
some editors add them as a kind of "magic number" identifying a UTF-8 encoded file.
</p>
<p>
<em>Updating</em>:
Most programs will be unaffected by the surrogate change.
Programs that depend on the old behavior should be modified to avoid the issue.
The byte-order-mark change is strictly backwards- compatible.
</p>
<h3 id="asm">Assembler</h3>
<p>
@ -127,7 +174,7 @@ package code.google.com/p/foo/quxx: cannot download, $GOPATH must not be set to
<p>
The <code>go fix</code> command no longer applies fixes to update code from
before Go 1 to use Go 1 APIs. To update pre-Go 1 code to Go 1.1, use a Go 1.0 toolchain
before Go 1 to use Go 1 APIs. To update pre-Go 1 code to Go 1.1, use a Go 1.0 tool chain
to convert the code to Go 1.0 first.
</p>
@ -176,7 +223,7 @@ The same is true of the other protocol-specific resolvers <code>ResolveIPAddr</c
<p>
The previous <code>ListenUnixgram</code> returned <code>UDPConn</code> as
arepresentation of the connection endpoint. The Go 1.1 implementation
a representation of the connection endpoint. The Go 1.1 implementation
returns <code>UnixConn</code> to allow reading and writing
with <code>ReadFrom</code> and <code>WriteTo</code> methods on
the <code>UnixConn</code>.
@ -381,7 +428,7 @@ The new method <a href="/pkg/os/#FileMode.IsRegular"><code>os.FileMode.IsRegular
<li>
The <a href="/pkg/regexp/"><code>regexp</code></a> package
now supports Unix-original lefmost-longest matches through the
now supports Unix-original leftmost-longest matches through the
<a href="/pkg/regexp/#Regexp.Longest"><code>Regexp.Longest</code></a>
method, while
<a href="/pkg/regexp/#Regexp.Split"><code>Regexp.Split</code></a> slices