golang init 代码
文件路径：/src/cmd/compile/internal/pkginit/init.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 pkginit
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/noder"
"cmd/compile/internal/objw"
"cmd/compile/internal/staticinit"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/src"
)
/ MakeInit creates a synthetic init function to handle any
/ package-scope initialization statements.
/
/ TODO(mdempsky): Move into noder, so that the types2-based frontends
/ can use Info.InitOrder instead.
func MakeInit() {
nf := initOrder(typecheck.Target.Decls)
if len(nf) == 0 {
return
}
/ Make a function that contains all the initialization statements.
base.Pos = nf[0].Pos() / prolog/epilog gets line number of first init stmt
initializers := typecheck.Lookup("init")
fn := typecheck.DeclFunc(initializers, nil, nil, nil)
for _, dcl := range typecheck.InitTodoFunc.Dcl {
dcl.Curfn = fn
}
fn.Dcl = append(fn.Dcl, typecheck.InitTodoFunc.Dcl...)
typecheck.InitTodoFunc.Dcl = nil
/ Suppress useless "can inline" diagnostics.
/ Init functions are only called dynamically.
fn.SetInlinabilityChecked(true)
fn.Body = nf
typecheck.FinishFuncBody()
typecheck.Func(fn)
ir.WithFunc(fn, func() {
typecheck.Stmts(nf)
})
typecheck.Target.Decls = append(typecheck.Target.Decls, fn)
/ Prepend to Inits, so it runs first, before any user-declared init
/ functions.
typecheck.Target.Inits = append([]*ir.Func{fn}, typecheck.Target.Inits...)
if typecheck.InitTodoFunc.Dcl != nil {
/ We only generate temps using InitTodoFunc if there
/ are package-scope initialization statements, so
/ something's weird if we get here.
base.Fatalf("InitTodoFunc still has declarations")
}
typecheck.InitTodoFunc = nil
}
/ Task makes and returns an initialization record for the package.
/ See runtime/proc.go:initTask for its layout.
/ The 3 tasks for initialization are:
/ 1. Initialize all of the packages the current package depends on.
/ 2. Initialize all the variables that have initializers.
/ 3. Run any init functions.
func Task() *ir.Name {
var deps []*obj.LSym / initTask records for packages the current package depends on
var fns []*obj.LSym / functions to call for package initialization
/ Find imported packages with init tasks.
for _, pkg := range typecheck.Target.Imports {
n := typecheck.Resolve(ir.NewIdent(base.Pos, pkg.Lookup(".inittask")))
if n.Op() == ir.ONONAME {
continue
}
if n.Op() != ir.ONAME || n.(*ir.Name).Class != ir.PEXTERN {
base.Fatalf("bad inittask: %v", n)
}
deps = append(deps, n.(*ir.Name).Linksym())
}
if base.Flag.ASan {
/ Make an initialization function to call runtime.asanregisterglobals to register an
/ array of instrumented global variables when -asan is enabled. An instrumented global
/ variable is described by a structure.
/ See the _asan_global structure declared in src/runtime/asan/asan.go.
/
/ func init {
/ var globals []_asan_global {...}
/ asanregisterglobals(&globals[0], len(globals))
/ }
for _, n := range typecheck.Target.Externs {
if canInstrumentGlobal(n) {
name := n.Sym().Name
InstrumentGlobalsMap[name] = n
InstrumentGlobalsSlice = append(InstrumentGlobalsSlice, n)
}
}
ni := len(InstrumentGlobalsMap)
if ni != 0 {
/ Make an init._ function.
base.Pos = base.AutogeneratedPos
typecheck.DeclContext = ir.PEXTERN
name := noder.Renameinit()
fnInit := typecheck.DeclFunc(name, nil, nil, nil)
/ Get an array of intrumented global variables.
globals := instrumentGlobals(fnInit)
/ Call runtime.asanregisterglobals function to poison redzones.
/ runtime.asanregisterglobals(unsafe.Pointer(&globals[0]), ni)
asanf := typecheck.NewName(ir.Pkgs.Runtime.Lookup("asanregisterglobals"))
ir.MarkFunc(asanf)
asanf.SetType(types.NewSignature(types.NoPkg, nil, nil, []*types.Field{
types.NewField(base.Pos, nil, types.Types[types.TUNSAFEPTR]),
types.NewField(base.Pos, nil, types.Types[types.TUINTPTR]),
}, nil))
asancall := ir.NewCallExpr(base.Pos, ir.OCALL, asanf, nil)
asancall.Args.Append(typecheck.ConvNop(typecheck.NodAddr(
ir.NewIndexExpr(base.Pos, globals, ir.NewInt(0))), types.Types[types.TUNSAFEPTR]))
asancall.Args.Append(typecheck.ConvNop(ir.NewInt(int64(ni)), types.Types[types.TUINTPTR]))
fnInit.Body.Append(asancall)
typecheck.FinishFuncBody()
typecheck.Func(fnInit)
ir.CurFunc = fnInit
typecheck.Stmts(fnInit.Body)
ir.CurFunc = nil
typecheck.Target.Decls = append(typecheck.Target.Decls, fnInit)
typecheck.Target.Inits = append(typecheck.Target.Inits, fnInit)
}
}
/ Record user init functions.
for _, fn := range typecheck.Target.Inits {
if fn.Sym().Name == "init" {
/ Synthetic init function for initialization of package-scope
/ variables. We can use staticinit to optimize away static
/ assignments.
s := staticinit.Schedule{
Plans: make(map[ir.Node]*staticinit.Plan),
Temps: make(map[ir.Node]*ir.Name),
}
for _, n := range fn.Body {
s.StaticInit(n)
}
fn.Body = s.Out
ir.WithFunc(fn, func() {
typecheck.Stmts(fn.Body)
})
if len(fn.Body) == 0 {
fn.Body = []ir.Node{ir.NewBlockStmt(src.NoXPos, nil)}
}
}
/ Skip init functions with empty bodies.
if len(fn.Body) == 1 {
if stmt := fn.Body[0]; stmt.Op() == ir.OBLOCK && len(stmt.(*ir.BlockStmt).List) == 0 {
continue
}
}
fns = append(fns, fn.Nname.Linksym())
}
if len(deps) == 0 && len(fns) == 0 && types.LocalPkg.Path != "main" && types.LocalPkg.Path != "runtime" {
return nil / nothing to initialize
}
/ Make an .inittask structure.
sym := typecheck.Lookup(".inittask")
task := typecheck.NewName(sym)
task.SetType(types.Types[types.TUINT8]) / fake type
task.Class = ir.PEXTERN
sym.Def = task
lsym := task.Linksym()
ot := 0
ot = objw.Uintptr(lsym, ot, 0) / state: not initialized yet
ot = objw.Uintptr(lsym, ot, uint64(len(deps)))
ot = objw.Uintptr(lsym, ot, uint64(len(fns)))
for _, d := range deps {
ot = objw.SymPtr(lsym, ot, d, 0)
}
for _, f := range fns {
ot = objw.SymPtr(lsym, ot, f, 0)
}
/ An initTask has pointers, but none into the Go heap.
/ It's not quite read only, the state field must be modifiable.
objw.Global(lsym, int32(ot), obj.NOPTR)
return task
}