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go/src/runtime/runtime.go
Russ Cox 193daab988 cmd/cc, cmd/ld, runtime: disallow conservative data/bss objects
In linker, refuse to write conservative (array of pointers) as the
garbage collection type for any variable in the data/bss GC program.

In the linker, attach the Go type to an already-read C declaration
during dedup. This gives us Go types for C globals for free as long
as the cmd/dist-generated Go code contains the declaration.
(Most runtime C declarations have a corresponding Go declaration.
Both are bss declarations and so the linker dedups them.)

In cmd/dist, add a few more C files to the auto-Go-declaration list
in order to get Go type information for the C declarations into the linker.

In C compiler, mark all non-pointer-containing global declarations
and all string data as NOPTR. This allows them to exist in C files
without any corresponding Go declaration. Count C function pointers
as "non-pointer-containing", since we have no heap-allocated C functions.

In runtime, add NOPTR to the remaining pointer-containing declarations,
none of which refer to Go heap objects.

In runtime, also move os.Args and syscall.envs data into runtime-owned
variables. Otherwise, in programs that do not import os or syscall, the
runtime variables named os.Args and syscall.envs will be missing type
information.

I believe that this CL eliminates the final source of conservative GC scanning
in non-SWIG Go programs, and therefore...

Fixes #909.

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/149770043
2014-09-24 16:55:26 -04:00

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1.2 KiB
Go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime
var ticks struct {
lock mutex
val uint64
}
var tls0 [8]uintptr // available storage for m0's TLS; not necessarily used; opaque to GC
// Note: Called by runtime/pprof in addition to runtime code.
func tickspersecond() int64 {
r := int64(atomicload64(&ticks.val))
if r != 0 {
return r
}
lock(&ticks.lock)
r = int64(ticks.val)
if r == 0 {
t0 := nanotime()
c0 := cputicks()
usleep(100 * 1000)
t1 := nanotime()
c1 := cputicks()
if t1 == t0 {
t1++
}
r = (c1 - c0) * 1000 * 1000 * 1000 / (t1 - t0)
if r == 0 {
r++
}
atomicstore64(&ticks.val, uint64(r))
}
unlock(&ticks.lock)
return r
}
func makeStringSlice(n int) []string {
return make([]string, n)
}
// TODO: Move to parfor.go when parfor.c becomes parfor.go.
func parforalloc(nthrmax uint32) *parfor {
return &parfor{
thr: &make([]parforthread, nthrmax)[0],
nthrmax: nthrmax,
}
}
var envs []string
var argslice []string
// called from syscall
func runtime_envs() []string { return envs }
// called from os
func runtime_args() []string { return argslice }