Add labels to tasks (#45)

vendor/honnef.co/go/tools/callgraph/callgraph.go

@@ -0,0 +1,129 @@
+// 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 callgraph defines the call graph and various algorithms
+and utilities to operate on it.
+
+A call graph is a labelled directed graph whose nodes represent
+functions and whose edge labels represent syntactic function call
+sites.  The presence of a labelled edge (caller, site, callee)
+indicates that caller may call callee at the specified call site.
+
+A call graph is a multigraph: it may contain multiple edges (caller,
+*, callee) connecting the same pair of nodes, so long as the edges
+differ by label; this occurs when one function calls another function
+from multiple call sites.  Also, it may contain multiple edges
+(caller, site, *) that differ only by callee; this indicates a
+polymorphic call.
+
+A SOUND call graph is one that overapproximates the dynamic calling
+behaviors of the program in all possible executions.  One call graph
+is more PRECISE than another if it is a smaller overapproximation of
+the dynamic behavior.
+
+All call graphs have a synthetic root node which is responsible for
+calling main() and init().
+
+Calls to built-in functions (e.g. panic, println) are not represented
+in the call graph; they are treated like built-in operators of the
+language.
+
+*/
+package callgraph // import "honnef.co/go/tools/callgraph"
+
+// TODO(adonovan): add a function to eliminate wrappers from the
+// callgraph, preserving topology.
+// More generally, we could eliminate "uninteresting" nodes such as
+// nodes from packages we don't care about.
+
+import (
+	"fmt"
+	"go/token"
+
+	"honnef.co/go/tools/ssa"
+)
+
+// A Graph represents a call graph.
+//
+// A graph may contain nodes that are not reachable from the root.
+// If the call graph is sound, such nodes indicate unreachable
+// functions.
+//
+type Graph struct {
+	Root  *Node                   // the distinguished root node
+	Nodes map[*ssa.Function]*Node // all nodes by function
+}
+
+// New returns a new Graph with the specified root node.
+func New(root *ssa.Function) *Graph {
+	g := &Graph{Nodes: make(map[*ssa.Function]*Node)}
+	g.Root = g.CreateNode(root)
+	return g
+}
+
+// CreateNode returns the Node for fn, creating it if not present.
+func (g *Graph) CreateNode(fn *ssa.Function) *Node {
+	n, ok := g.Nodes[fn]
+	if !ok {
+		n = &Node{Func: fn, ID: len(g.Nodes)}
+		g.Nodes[fn] = n
+	}
+	return n
+}
+
+// A Node represents a node in a call graph.
+type Node struct {
+	Func *ssa.Function // the function this node represents
+	ID   int           // 0-based sequence number
+	In   []*Edge       // unordered set of incoming call edges (n.In[*].Callee == n)
+	Out  []*Edge       // unordered set of outgoing call edges (n.Out[*].Caller == n)
+}
+
+func (n *Node) String() string {
+	return fmt.Sprintf("n%d:%s", n.ID, n.Func)
+}
+
+// A Edge represents an edge in the call graph.
+//
+// Site is nil for edges originating in synthetic or intrinsic
+// functions, e.g. reflect.Call or the root of the call graph.
+type Edge struct {
+	Caller *Node
+	Site   ssa.CallInstruction
+	Callee *Node
+}
+
+func (e Edge) String() string {
+	return fmt.Sprintf("%s --> %s", e.Caller, e.Callee)
+}
+
+func (e Edge) Description() string {
+	var prefix string
+	switch e.Site.(type) {
+	case nil:
+		return "synthetic call"
+	case *ssa.Go:
+		prefix = "concurrent "
+	case *ssa.Defer:
+		prefix = "deferred "
+	}
+	return prefix + e.Site.Common().Description()
+}
+
+func (e Edge) Pos() token.Pos {
+	if e.Site == nil {
+		return token.NoPos
+	}
+	return e.Site.Pos()
+}
+
+// AddEdge adds the edge (caller, site, callee) to the call graph.
+// Elimination of duplicate edges is the caller's responsibility.
+func AddEdge(caller *Node, site ssa.CallInstruction, callee *Node) {
+	e := &Edge{caller, site, callee}
+	callee.In = append(callee.In, e)
+	caller.Out = append(caller.Out, e)
+}

vendor/honnef.co/go/tools/callgraph/static/static.go

@@ -0,0 +1,35 @@
+// Package static computes the call graph of a Go program containing
+// only static call edges.
+package static // import "honnef.co/go/tools/callgraph/static"
+
+import (
+	"honnef.co/go/tools/callgraph"
+	"honnef.co/go/tools/ssa"
+	"honnef.co/go/tools/ssa/ssautil"
+)
+
+// CallGraph computes the call graph of the specified program
+// considering only static calls.
+//
+func CallGraph(prog *ssa.Program) *callgraph.Graph {
+	cg := callgraph.New(nil) // TODO(adonovan) eliminate concept of rooted callgraph
+
+	// TODO(adonovan): opt: use only a single pass over the ssa.Program.
+	// TODO(adonovan): opt: this is slower than RTA (perhaps because
+	// the lower precision means so many edges are allocated)!
+	for f := range ssautil.AllFunctions(prog) {
+		fnode := cg.CreateNode(f)
+		for _, b := range f.Blocks {
+			for _, instr := range b.Instrs {
+				if site, ok := instr.(ssa.CallInstruction); ok {
+					if g := site.Common().StaticCallee(); g != nil {
+						gnode := cg.CreateNode(g)
+						callgraph.AddEdge(fnode, site, gnode)
+					}
+				}
+			}
+		}
+	}
+
+	return cg
+}

vendor/honnef.co/go/tools/callgraph/util.go

@@ -0,0 +1,181 @@
+// 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 callgraph
+
+import "honnef.co/go/tools/ssa"
+
+// This file provides various utilities over call graphs, such as
+// visitation and path search.
+
+// CalleesOf returns a new set containing all direct callees of the
+// caller node.
+//
+func CalleesOf(caller *Node) map[*Node]bool {
+	callees := make(map[*Node]bool)
+	for _, e := range caller.Out {
+		callees[e.Callee] = true
+	}
+	return callees
+}
+
+// GraphVisitEdges visits all the edges in graph g in depth-first order.
+// The edge function is called for each edge in postorder.  If it
+// returns non-nil, visitation stops and GraphVisitEdges returns that
+// value.
+//
+func GraphVisitEdges(g *Graph, edge func(*Edge) error) error {
+	seen := make(map[*Node]bool)
+	var visit func(n *Node) error
+	visit = func(n *Node) error {
+		if !seen[n] {
+			seen[n] = true
+			for _, e := range n.Out {
+				if err := visit(e.Callee); err != nil {
+					return err
+				}
+				if err := edge(e); err != nil {
+					return err
+				}
+			}
+		}
+		return nil
+	}
+	for _, n := range g.Nodes {
+		if err := visit(n); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// PathSearch finds an arbitrary path starting at node start and
+// ending at some node for which isEnd() returns true.  On success,
+// PathSearch returns the path as an ordered list of edges; on
+// failure, it returns nil.
+//
+func PathSearch(start *Node, isEnd func(*Node) bool) []*Edge {
+	stack := make([]*Edge, 0, 32)
+	seen := make(map[*Node]bool)
+	var search func(n *Node) []*Edge
+	search = func(n *Node) []*Edge {
+		if !seen[n] {
+			seen[n] = true
+			if isEnd(n) {
+				return stack
+			}
+			for _, e := range n.Out {
+				stack = append(stack, e) // push
+				if found := search(e.Callee); found != nil {
+					return found
+				}
+				stack = stack[:len(stack)-1] // pop
+			}
+		}
+		return nil
+	}
+	return search(start)
+}
+
+// DeleteSyntheticNodes removes from call graph g all nodes for
+// synthetic functions (except g.Root and package initializers),
+// preserving the topology.  In effect, calls to synthetic wrappers
+// are "inlined".
+//
+func (g *Graph) DeleteSyntheticNodes() {
+	// Measurements on the standard library and go.tools show that
+	// resulting graph has ~15% fewer nodes and 4-8% fewer edges
+	// than the input.
+	//
+	// Inlining a wrapper of in-degree m, out-degree n adds m*n
+	// and removes m+n edges.  Since most wrappers are monomorphic
+	// (n=1) this results in a slight reduction.  Polymorphic
+	// wrappers (n>1), e.g. from embedding an interface value
+	// inside a struct to satisfy some interface, cause an
+	// increase in the graph, but they seem to be uncommon.
+
+	// Hash all existing edges to avoid creating duplicates.
+	edges := make(map[Edge]bool)
+	for _, cgn := range g.Nodes {
+		for _, e := range cgn.Out {
+			edges[*e] = true
+		}
+	}
+	for fn, cgn := range g.Nodes {
+		if cgn == g.Root || fn.Synthetic == "" || isInit(cgn.Func) {
+			continue // keep
+		}
+		for _, eIn := range cgn.In {
+			for _, eOut := range cgn.Out {
+				newEdge := Edge{eIn.Caller, eIn.Site, eOut.Callee}
+				if edges[newEdge] {
+					continue // don't add duplicate
+				}
+				AddEdge(eIn.Caller, eIn.Site, eOut.Callee)
+				edges[newEdge] = true
+			}
+		}
+		g.DeleteNode(cgn)
+	}
+}
+
+func isInit(fn *ssa.Function) bool {
+	return fn.Pkg != nil && fn.Pkg.Func("init") == fn
+}
+
+// DeleteNode removes node n and its edges from the graph g.
+// (NB: not efficient for batch deletion.)
+func (g *Graph) DeleteNode(n *Node) {
+	n.deleteIns()
+	n.deleteOuts()
+	delete(g.Nodes, n.Func)
+}
+
+// deleteIns deletes all incoming edges to n.
+func (n *Node) deleteIns() {
+	for _, e := range n.In {
+		removeOutEdge(e)
+	}
+	n.In = nil
+}
+
+// deleteOuts deletes all outgoing edges from n.
+func (n *Node) deleteOuts() {
+	for _, e := range n.Out {
+		removeInEdge(e)
+	}
+	n.Out = nil
+}
+
+// removeOutEdge removes edge.Caller's outgoing edge 'edge'.
+func removeOutEdge(edge *Edge) {
+	caller := edge.Caller
+	n := len(caller.Out)
+	for i, e := range caller.Out {
+		if e == edge {
+			// Replace it with the final element and shrink the slice.
+			caller.Out[i] = caller.Out[n-1]
+			caller.Out[n-1] = nil // aid GC
+			caller.Out = caller.Out[:n-1]
+			return
+		}
+	}
+	panic("edge not found: " + edge.String())
+}
+
+// removeInEdge removes edge.Callee's incoming edge 'edge'.
+func removeInEdge(edge *Edge) {
+	caller := edge.Callee
+	n := len(caller.In)
+	for i, e := range caller.In {
+		if e == edge {
+			// Replace it with the final element and shrink the slice.
+			caller.In[i] = caller.In[n-1]
+			caller.In[n-1] = nil // aid GC
+			caller.In = caller.In[:n-1]
+			return
+		}
+	}
+	panic("edge not found: " + edge.String())
+}