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The Go programming language
eb592d8289
The escape analysis works by tracing assignment paths from
variables that start with pointer type, or addresses of variables
(addresses are always pointers). It does allow non-pointers
in the path, so that in this code it sees x's value escape into y:
var x *[10]int
y := (*int)(unsafe.Pointer(uintptr(unsafe.Pointer(x))+32))
It must allow uintptr in order to see through this kind of
"pointer arithmetic".
It also traces such values if they end up as uintptrs passed to
functions. This used to be important because packages like
encoding/gob passed around uintptrs holding real pointers.
The introduction of precise collection of stacks has forced
code to be more honest about which declared stack variables
hold pointers and which do not. In particular, the garbage
collector no longer sees pointers stored in uintptr variables.
Because of this, packages like encoding/gob have been fixed.
There is not much point in the escape analysis accepting
uintptrs as holding pointers at call boundaries if the garbage
collector does not.
Excluding uintptr-valued arguments brings the escape
analysis in line with the garbage collector and has the
useful side effect of making arguments to syscall.Syscall
not appear to escape.
That is, this CL should yield the same benefits as
CL 45930043 (rolled back in CL 53870043), but it does
so by making uintptrs less special, not more.
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/53940043
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This is the source code repository for the Go programming language.
For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install-source.html
in your web browser.
After installing Go, you can view a nicely formatted
doc/install-source.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install/source.
Unless otherwise noted, the Go source files are distributed
under the BSD-style license found in the LICENSE file.
--
Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set
the environment variable $GOROOT to the full path of the go
directory (the one containing this README). You can omit the
variable if you unpack it into /usr/local/go, or if you rebuild
from sources by running all.bash (see doc/install.html).
You should also add the Go binary directory $GOROOT/bin
to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might
put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See doc/install.html for more details.