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// Copyright 2013 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 oracle
import (
"fmt"
"go/ast"
"go/token"
"sort"
"code.google.com/p/go.tools/go/ssa"
"code.google.com/p/go.tools/go/types"
"code.google.com/p/go.tools/oracle/serial"
)
// Callees reports the possible callees of the function call site
// identified by the specified source location.
func callees(o *Oracle, qpos *QueryPos) (queryResult, error) {
pkg := o.prog.Package(qpos.info.Pkg)
if pkg == nil {
return nil, fmt.Errorf("no SSA package")
}
// Determine the enclosing call for the specified position.
var e *ast.CallExpr
for _, n := range qpos.path {
if e, _ = n.(*ast.CallExpr); e != nil {
break
}
}
if e == nil {
return nil, fmt.Errorf("there is no function call here")
}
// TODO(adonovan): issue an error if the call is "too far
// away" from the current selection, as this most likely is
// not what the user intended.
// Reject type conversions.
if qpos.info.IsType(e.Fun) {
return nil, fmt.Errorf("this is a type conversion, not a function call")
}
// Reject calls to built-ins.
if id, ok := unparen(e.Fun).(*ast.Ident); ok {
if b, ok := qpos.info.ObjectOf(id).(*types.Builtin); ok {
return nil, fmt.Errorf("this is a call to the built-in '%s' operator", b.Name())
}
}
buildSSA(o)
// Ascertain calling function and call site.
callerFn := ssa.EnclosingFunction(pkg, qpos.path)
if callerFn == nil {
return nil, fmt.Errorf("no SSA function built for this location (dead code?)")
}
// Find the call site.
site, err := findCallSite(callerFn, e.Lparen)
if err != nil {
return nil, err
}
funcs, err := findCallees(o, site)
if err != nil {
return nil, err
}
return &calleesResult{
site: site,
funcs: funcs,
}, nil
}
func findCallSite(fn *ssa.Function, lparen token.Pos) (ssa.CallInstruction, error) {
for _, b := range fn.Blocks {
for _, instr := range b.Instrs {
if site, ok := instr.(ssa.CallInstruction); ok && instr.Pos() == lparen {
return site, nil
}
}
}
return nil, fmt.Errorf("this call site is unreachable in this analysis")
}
func findCallees(o *Oracle, site ssa.CallInstruction) ([]*ssa.Function, error) {
// Avoid running the pointer analysis for static calls.
if callee := site.Common().StaticCallee(); callee != nil {
switch callee.String() {
case "runtime.SetFinalizer", "(reflect.Value).Call":
// The PTA treats calls to these intrinsics as dynamic.
// TODO(adonovan): avoid reliance on PTA internals.
default:
return []*ssa.Function{callee}, nil // singleton
}
}
// Dynamic call: use pointer analysis.
o.ptaConfig.BuildCallGraph = true
cg := ptrAnalysis(o).CallGraph
cg.DeleteSyntheticNodes()
// Find all call edges from the site.
n := cg.Nodes[site.Parent()]
if n == nil {
return nil, fmt.Errorf("this call site is unreachable in this analysis")
}
calleesMap := make(map[*ssa.Function]bool)
for _, edge := range n.Out {
if edge.Site == site {
calleesMap[edge.Callee.Func] = true
}
}
// De-duplicate and sort.
funcs := make([]*ssa.Function, 0, len(calleesMap))
for f := range calleesMap {
funcs = append(funcs, f)
}
sort.Sort(byFuncPos(funcs))
return funcs, nil
}
type calleesResult struct {
site ssa.CallInstruction
funcs []*ssa.Function
}
func (r *calleesResult) display(printf printfFunc) {
if len(r.funcs) == 0 {
// dynamic call on a provably nil func/interface
printf(r.site, "%s on nil value", r.site.Common().Description())
} else {
printf(r.site, "this %s dispatches to:", r.site.Common().Description())
for _, callee := range r.funcs {
printf(callee, "\t%s", callee)
}
}
}
func (r *calleesResult) toSerial(res *serial.Result, fset *token.FileSet) {
j := &serial.Callees{
Pos: fset.Position(r.site.Pos()).String(),
Desc: r.site.Common().Description(),
}
for _, callee := range r.funcs {
j.Callees = append(j.Callees, &serial.CalleesItem{
Name: callee.String(),
Pos: fset.Position(callee.Pos()).String(),
})
}
res.Callees = j
}
type byFuncPos []*ssa.Function
func (a byFuncPos) Len() int { return len(a) }
func (a byFuncPos) Less(i, j int) bool { return a[i].Pos() < a[j].Pos() }
func (a byFuncPos) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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