From 04b08da9af0c450d645ab7389d1467308cfc2db8 Mon Sep 17 00:00:00 2001 From: Michael Stapelberg Date: Mon, 4 Mar 2013 21:27:36 +0100 Subject: Imported Upstream version 1.1~hg20130304 --- doc/go1.1.html | 207 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 207 insertions(+) create mode 100644 doc/go1.1.html (limited to 'doc/go1.1.html') diff --git a/doc/go1.1.html b/doc/go1.1.html new file mode 100644 index 000000000..ae0a09939 --- /dev/null +++ b/doc/go1.1.html @@ -0,0 +1,207 @@ + + +

Introduction to Go 1.1

+ +TODO + - overview + - link back to Go 1 and also Go 1 Compatibility docs. + +

Changes to the language

+ +TODO + +

Integer division by zero

+ +

+In Go 1, integer division by a constant zero produced a runtime panic: +

+ +
+func f(x int) int {
+	return x/0
+}
+
+ +

+In Go 1.1, an integer division by constant zero is not a legal program, so it is a compile-time error. +

+ + +

Changes to the implementations and tools

+ +TODO: more + +

Command-line flag parsing

+ +

+In the gc toolchain, 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. +For example, +go tool 6c -Fw -Dfoo must now be written +go tool 6c -F -w -D foo. +

+ +

Size of int on 64-bit platforms

+ +

+The language allows the implementation to choose whether the int type and uint types are 32 or 64 bits. Previous Go implementations made int and uint 32 bits on all systems. Both the gc and gccgo implementations (TODO: check that gccgo does) now make int and uint 64 bits on 64-bit platforms such as AMD64/x86-64. +Among other things, this enables the allocation of slices with +more than 2 billion elements on 64-bit platforms. +

+ +

+Updating: +Most programs will be unaffected by this change. +Because Go does not allow implicit conversions between distinct +numeric types, +no programs will stop compiling due to this change. +However, programs that contain implicit assumptions +that int is only 32 bits may change behavior. +For example, this code prints a positive number on 64-bit systems and +a negative one on 32-bit systems: + +

+x := ^uint32(0) // x is 0xffffffff
+i := int(x)     // i is -1 on 32-bit systems, 0xffffffff on 64-bit
+fmt.Println(i)
+
+ +

Portable code intending 32-bit sign extension (yielding -1 on all systems) +would instead say: +

+ +
+i := int(int32(x))
+
+ +

Assembler

+ +

+Due to the int and TODO: OTHER changes, +the placement of function arguments on the stack has changed. +Functions written in assembly will need to be revised at least +to adjust frame pointer offsets. +

+ +

Changes to the go tool

+ +

The go tool has acquired several improvements which are intended to improve the experience for new Go users.

+ +

Firstly, when compiling, testing, or running Go code, the go tool will now give more detailed errors messages, including a list of paths searched, when a package cannot be located. +

+ +
+$ go build foo/quxx
+can't load package: package foo/quxx: cannot find package "foo/quxx" in any of:
+        /home/User/go/src/pkg/foo/quxx (from $GOROOT)
+        /home/User/src/foo/quxx (from $GOPATH) 
+
+ +

+Secondly, the go get command no longer allows $GOROOT as the default destination when downloading package source. To use go get command, a valid $GOPATH is now required. +

+ +
+$ GOPATH= go get code.google.com/p/foo/quxx
+package code.google.com/p/foo/quxx: cannot download, $GOPATH not set. For more details see: go help gopath 
+
+ +

Finally, as a result of the previous change, the go get command will also fail when $GOPATH and $GOROOT are set to the same value. +

+ +
+$ GOPATH=$GOROOT go get code.google.com/p/foo/quxx
+warning: GOPATH set to GOROOT (/home/User/go) has no effect
+package code.google.com/p/foo/quxx: cannot download, $GOPATH must not be set to $GOROOT. For more details see: go help gopath
+
+ +

Changes to go fix

+ +

+The go fix 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 +to convert the code to Go 1.0 first. +

+ +

Changes to the standard library

+ +

debug/elf

+

+Previous versions of the debug/elf package intentionally skipped over the first +symbol in the ELF symbol table, since it is always an empty symbol. This symbol +is no longer skipped since indexes into the symbol table returned by debug/elf, +will be different to indexes into the original ELF symbol table. Any code that +calls the debug/elf functions Symbols or ImportedSymbols may need to be +adjusted to account for the additional symbol and the change in symbol offsets. +

+ +

html/template

+ +

+Templates using the undocumented and only partially implemented +"noescape" feature will break: that feature was removed. +

+ +

net

+ +

+The protocol-specific resolvers were formerly +lax about the network name passed in. For example, although the documentation was clear +that the only valid networks for ResolveTCPAddr are "tcp", +"tcp4", and "tcp6", the Go 1.0 implementation silently accepted +any string. The Go 1.1 implementation returns an error if the network is not one of those strings. +The same is true of the other protocol-specific resolvers ResolveIPAddr, ResolveUDPAddr, and +ResolveUnixAddr. +

+ +

+The previous ListenUnixgram returned UDPConn as +arepresentation of the connection endpoint. The Go 1.1 implementation +returns UnixConn to allow reading and writing +with ReadFrom and WriteTo methods on +the UnixConn. +

+ +

time

+

+On FreeBSD, Linux, NetBSD, OS X and OpenBSD, previous versions of the time package +returned times with microsecond precision. The Go 1.1 implementation of time on these +systems now returns times with nanosecond precision. Code may exist that expects to be +able to store such a time in an external format with only microsecond precision, +read it back, and recover exactly the same time instant. +In Go 1.1 the same time will not be recovered, since the external storage +will have discarded nanoseconds. +To address this case, there are two new methods of time.Time, Round and Truncate, +that can be used to remove precision from a time before passing it to +external storage. +

+ +

Exp and old subtrees moved to go.exp subrepo

+ +

+To make it easier for binary distributions to access them if desired, the exp +and old source subtrees, which are not included in binary distributions, +have been moved to the new go.exp subrepository at +code.google.com/p/go.exp. To access the ssa package, +for example, run +

+ +
+$ go get code.google.com/p/go.exp/ssa
+
+ +

+and then in Go source, +

+ +
+import "code.google.com/p/go.exp/ssa"
+
+ +

TODO

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