Add gops agent

vendor/github.com/google/gops/internal/obj/obj.go

@@ -0,0 +1,306 @@
+// 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 obj
+
+import (
+	"fmt"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// A LineHist records the history of the file input stack, which maps the virtual line number,
+// an incrementing count of lines processed in any input file and typically named lineno,
+// to a stack of file:line pairs showing the path of inclusions that led to that position.
+// The first line directive (//line in Go, #line in assembly) is treated as pushing
+// a new entry on the stack, so that errors can report both the actual and translated
+// line number.
+//
+// In typical use, the virtual lineno begins at 1, and file line numbers also begin at 1,
+// but the only requirements placed upon the numbers by this code are:
+//	- calls to Push, Update, and Pop must be monotonically increasing in lineno
+//	- except as specified by those methods, virtual and file line number increase
+//	  together, so that given (only) calls Push(10, "x.go", 1) and Pop(15),
+//	  virtual line 12 corresponds to x.go line 3.
+type LineHist struct {
+	Top               *LineStack  // current top of stack
+	Ranges            []LineRange // ranges for lookup
+	Dir               string      // directory to qualify relative paths
+	TrimPathPrefix    string      // remove leading TrimPath from recorded file names
+	PrintFilenameOnly bool        // ignore path when pretty-printing a line; internal use only
+	GOROOT            string      // current GOROOT
+}
+
+// A LineStack is an entry in the recorded line history.
+// Although the history at any given line number is a stack,
+// the record for all line processed forms a tree, with common
+// stack prefixes acting as parents.
+type LineStack struct {
+	Parent    *LineStack // parent in inclusion stack
+	Lineno    int        // virtual line number where this entry takes effect
+	File      string     // file name used to open source file, for error messages
+	AbsFile   string     // absolute file name, for pcln tables
+	FileLine  int        // line number in file at Lineno
+	Directive bool
+	Sym       *LSym // for linkgetline - TODO(rsc): remove
+}
+
+func (stk *LineStack) fileLineAt(lineno int) int {
+	return stk.FileLine + lineno - stk.Lineno
+}
+
+// The span of valid linenos in the recorded line history can be broken
+// into a set of ranges, each with a particular stack.
+// A LineRange records one such range.
+type LineRange struct {
+	Start int        // starting lineno
+	Stack *LineStack // top of stack for this range
+}
+
+// startRange starts a new range with the given top of stack.
+func (h *LineHist) startRange(lineno int, top *LineStack) {
+	h.Top = top
+	h.Ranges = append(h.Ranges, LineRange{top.Lineno, top})
+}
+
+// setFile sets stk.File = file and also derives stk.AbsFile.
+func (h *LineHist) setFile(stk *LineStack, file string) {
+	// Note: The exclusion of stk.Directive may be wrong but matches what we've done before.
+	// The check for < avoids putting a path prefix on "<autogenerated>".
+	abs := file
+	if h.Dir != "" && !filepath.IsAbs(file) && !strings.HasPrefix(file, "<") && !stk.Directive {
+		abs = filepath.Join(h.Dir, file)
+	}
+
+	// Remove leading TrimPathPrefix, or else rewrite $GOROOT to literal $GOROOT.
+	if h.TrimPathPrefix != "" && hasPathPrefix(abs, h.TrimPathPrefix) {
+		if abs == h.TrimPathPrefix {
+			abs = ""
+		} else {
+			abs = abs[len(h.TrimPathPrefix)+1:]
+		}
+	} else if hasPathPrefix(abs, h.GOROOT) {
+		abs = "$GOROOT" + abs[len(h.GOROOT):]
+	}
+	if abs == "" {
+		abs = "??"
+	}
+	abs = filepath.Clean(abs)
+	stk.AbsFile = abs
+
+	if file == "" {
+		file = "??"
+	}
+	stk.File = file
+}
+
+// Does s have t as a path prefix?
+// That is, does s == t or does s begin with t followed by a slash?
+// For portability, we allow ASCII case folding, so that hasPathPrefix("a/b/c", "A/B") is true.
+// Similarly, we allow slash folding, so that hasPathPrefix("a/b/c", "a\\b") is true.
+// We do not allow full Unicode case folding, for fear of causing more confusion
+// or harm than good. (For an example of the kinds of things that can go wrong,
+// see http://article.gmane.org/gmane.linux.kernel/1853266.)
+func hasPathPrefix(s string, t string) bool {
+	if len(t) > len(s) {
+		return false
+	}
+	var i int
+	for i = 0; i < len(t); i++ {
+		cs := int(s[i])
+		ct := int(t[i])
+		if 'A' <= cs && cs <= 'Z' {
+			cs += 'a' - 'A'
+		}
+		if 'A' <= ct && ct <= 'Z' {
+			ct += 'a' - 'A'
+		}
+		if cs == '\\' {
+			cs = '/'
+		}
+		if ct == '\\' {
+			ct = '/'
+		}
+		if cs != ct {
+			return false
+		}
+	}
+	return i >= len(s) || s[i] == '/' || s[i] == '\\'
+}
+
+// Push records that at that lineno a new file with the given name was pushed onto the input stack.
+func (h *LineHist) Push(lineno int, file string) {
+	stk := &LineStack{
+		Parent:   h.Top,
+		Lineno:   lineno,
+		FileLine: 1,
+	}
+	h.setFile(stk, file)
+	h.startRange(lineno, stk)
+}
+
+// Pop records that at lineno the current file was popped from the input stack.
+func (h *LineHist) Pop(lineno int) {
+	top := h.Top
+	if top == nil {
+		return
+	}
+	if top.Directive && top.Parent != nil { // pop #line level too
+		top = top.Parent
+	}
+	next := top.Parent
+	if next == nil {
+		h.Top = nil
+		h.Ranges = append(h.Ranges, LineRange{lineno, nil})
+		return
+	}
+
+	// Popping included file. Update parent offset to account for
+	// the virtual line number range taken by the included file.
+	// Cannot modify the LineStack directly, or else lookups
+	// for the earlier line numbers will get the wrong answers,
+	// so make a new one.
+	stk := new(LineStack)
+	*stk = *next
+	stk.Lineno = lineno
+	stk.FileLine = next.fileLineAt(top.Lineno)
+	h.startRange(lineno, stk)
+}
+
+// Update records that at lineno the file name and line number were changed using
+// a line directive (//line in Go, #line in assembly).
+func (h *LineHist) Update(lineno int, file string, line int) {
+	top := h.Top
+	if top == nil {
+		return // shouldn't happen
+	}
+	var stk *LineStack
+	if top.Directive {
+		// Update existing entry, except make copy to avoid changing earlier history.
+		stk = new(LineStack)
+		*stk = *top
+	} else {
+		// Push new entry.
+		stk = &LineStack{
+			Parent:    top,
+			Directive: true,
+		}
+	}
+	stk.Lineno = lineno
+	if stk.File != file {
+		h.setFile(stk, file) // only retain string if needed
+	}
+	stk.FileLine = line
+	h.startRange(lineno, stk)
+}
+
+// AddImport adds a package to the list of imported packages.
+func (ctxt *Link) AddImport(pkg string) {
+	ctxt.Imports = append(ctxt.Imports, pkg)
+}
+
+// At returns the input stack in effect at lineno.
+func (h *LineHist) At(lineno int) *LineStack {
+	i := sort.Search(len(h.Ranges), func(i int) bool {
+		return h.Ranges[i].Start > lineno
+	})
+	// Found first entry beyond lineno.
+	if i == 0 {
+		return nil
+	}
+	return h.Ranges[i-1].Stack
+}
+
+// LineString returns a string giving the file and line number
+// corresponding to lineno, for use in error messages.
+func (h *LineHist) LineString(lineno int) string {
+	stk := h.At(lineno)
+	if stk == nil {
+		return "<unknown line number>"
+	}
+
+	filename := stk.File
+	if h.PrintFilenameOnly {
+		filename = filepath.Base(filename)
+	}
+	text := fmt.Sprintf("%s:%d", filename, stk.fileLineAt(lineno))
+	if stk.Directive && stk.Parent != nil {
+		stk = stk.Parent
+		filename = stk.File
+		if h.PrintFilenameOnly {
+			filename = filepath.Base(filename)
+		}
+		text += fmt.Sprintf("[%s:%d]", filename, stk.fileLineAt(lineno))
+	}
+	const showFullStack = false // was used by old C compilers
+	if showFullStack {
+		for stk.Parent != nil {
+			lineno = stk.Lineno - 1
+			stk = stk.Parent
+			text += fmt.Sprintf(" %s:%d", filename, stk.fileLineAt(lineno))
+			if stk.Directive && stk.Parent != nil {
+				stk = stk.Parent
+				text += fmt.Sprintf("[%s:%d]", filename, stk.fileLineAt(lineno))
+			}
+		}
+	}
+	return text
+}
+
+// FileLine returns the file name and line number
+// at the top of the stack for the given lineno.
+func (h *LineHist) FileLine(lineno int) (file string, line int) {
+	stk := h.At(lineno)
+	if stk == nil {
+		return "??", 0
+	}
+	return stk.File, stk.fileLineAt(lineno)
+}
+
+// AbsFileLine returns the absolute file name and line number
+// at the top of the stack for the given lineno.
+func (h *LineHist) AbsFileLine(lineno int) (file string, line int) {
+	stk := h.At(lineno)
+	if stk == nil {
+		return "??", 0
+	}
+	return stk.AbsFile, stk.fileLineAt(lineno)
+}
+
+// This is a simplified copy of linklinefmt above.
+// It doesn't allow printing the full stack, and it returns the file name and line number separately.
+// TODO: Unify with linklinefmt somehow.
+func linkgetline(ctxt *Link, lineno int32) (f *LSym, l int32) {
+	stk := ctxt.LineHist.At(int(lineno))
+	if stk == nil || stk.AbsFile == "" {
+		return Linklookup(ctxt, "??", HistVersion), 0
+	}
+	if stk.Sym == nil {
+		stk.Sym = Linklookup(ctxt, stk.AbsFile, HistVersion)
+	}
+	return stk.Sym, int32(stk.fileLineAt(int(lineno)))
+}
+
+func Linkprfile(ctxt *Link, line int) {
+	fmt.Printf("%s ", ctxt.LineHist.LineString(line))
+}
+
+func fieldtrack(ctxt *Link, cursym *LSym) {
+	p := cursym.Text
+	if p == nil || p.Link == nil { // handle external functions and ELF section symbols
+		return
+	}
+	ctxt.Cursym = cursym
+
+	for ; p != nil; p = p.Link {
+		if p.As == AUSEFIELD {
+			r := Addrel(ctxt.Cursym)
+			r.Off = 0
+			r.Siz = 0
+			r.Sym = p.From.Sym
+			r.Type = R_USEFIELD
+		}
+	}
+}