Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/cgo: don't copy a simple variable x in &x[0]

Browse source 
Fixes #30065

Change-Id: I3d0fb03bab397548653d5f3b386cfe2980ac1030
Reviewed-on: https://go-review.googlesource.com/c/160830
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Ian Lance Taylor 2019-02-02 16:03:28 -08:00
parent 8f854244ad
commit 3fc276ccf8
3 changed files with 71 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

38
src/cmd/cgo/gcc.go
View file

@ -1121,14 +1121,19 @@ func (p *Package) mangle(f *File, arg *ast.Expr) (ast.Expr, bool) {
}
// checkIndex checks whether arg has the form &a[i], possibly inside
// type conversions. If so, it writes
// type conversions. If so, then in the general case it writes
// _cgoIndexNN := a
// _cgoNN := &cgoIndexNN[i] // with type conversions, if any
// to sb, and writes
// _cgoCheckPointer(_cgoNN, _cgoIndexNN)
// to sbCheck, and returns true. This tells _cgoCheckPointer to check
// the complete contents of the slice or array being indexed, but no
// other part of the memory allocation.
// to sbCheck, and returns true. If a is a simple variable or field reference,
// it writes
// _cgoIndexNN := &a
// and dereferences the uses of _cgoIndexNN. Taking the address avoids
// making a copy of an array.
//
// This tells _cgoCheckPointer to check the complete contents of the
// slice or array being indexed, but no other part of the memory allocation.
func (p *Package) checkIndex(sb, sbCheck *bytes.Buffer, arg ast.Expr, i int) bool {
// Strip type conversions.
x := arg
@ -1148,13 +1153,23 @@ func (p *Package) checkIndex(sb, sbCheck *bytes.Buffer, arg ast.Expr, i int) boo
return false
}
fmt.Fprintf(sb, "_cgoIndex%d := %s; ", i, gofmtPos(index.X, index.X.Pos()))
addr := ""
deref := ""
if p.isVariable(index.X) {
addr = "&"
deref = "*"
}
fmt.Fprintf(sb, "_cgoIndex%d := %s%s; ", i, addr, gofmtPos(index.X, index.X.Pos()))
origX := index.X
index.X = ast.NewIdent(fmt.Sprintf("_cgoIndex%d", i))
if deref == "*" {
index.X = &ast.StarExpr{X: index.X}
}
fmt.Fprintf(sb, "_cgo%d := %s; ", i, gofmtPos(arg, arg.Pos()))
index.X = origX
fmt.Fprintf(sbCheck, "_cgoCheckPointer(_cgo%d, _cgoIndex%d); ", i, i)
fmt.Fprintf(sbCheck, "_cgoCheckPointer(_cgo%d, %s_cgoIndex%d); ", i, deref, i)
return true
}
@ -1280,6 +1295,17 @@ func (p *Package) isConst(f *File, x ast.Expr) bool {
return false
}
// isVariable reports whether x is a variable, possibly with field references.
func (p *Package) isVariable(x ast.Expr) bool {
switch x := x.(type) {
case *ast.Ident:
return true
case *ast.SelectorExpr:
return p.isVariable(x.X)
}
return false
}
// rewriteUnsafe returns a version of t with references to unsafe.Pointer
// rewritten to use _cgo_unsafe.Pointer instead.
func (p *Package) rewriteUnsafe(t ast.Expr) ast.Expr {