code review 7393063: cmd/go: fix "go run" cgo source when cgo is disabled

src/cmd/go/run.go

 // Copyright 2011 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 main
 
 import (
         "fmt"
         "os"
         "os/exec"
@@ skipping 53 matching lines @@
         if p.Name != "main" {
                 fatalf("go run: cannot run non-main package")
         }
         p.target = "" // must build - not up to date
         var src string
         if len(p.GoFiles) > 0 {
                 src = p.GoFiles[0]
         } else if len(p.CgoFiles) > 0 {
                 src = p.CgoFiles[0]
         } else {
-                fatalf("go run: no suitable source file (cgo disabled?)")

[adg, 2013/02/26 22:01:11]

If we're going to give hints (and I have nothing against hints) then we should
give the correct hint; we have the information.

hint := "check build tags"
if buildContext.CgoDisabled {
  hint += ", cgo is disabled"
}
fatalf("go run: no suitable source file (%s)", hint)

+                // this case could only happen if the provided source uses cgo
+                // while cgo is disabled.
+                hint := ""
+                if !buildContext.CgoEnabled {
+                        hint = " (cgo is disabled)"
+                }
+                fatalf("go run: no suitable source files%s", hint)
         }
         p.exeName = src[:len(src)-len(".go")] // name temporary executable for first go file
         a1 := b.action(modeBuild, modeBuild, p)
         a := &action{f: (*builder).runProgram, args: cmdArgs, deps: []*action{a1}}
         b.do(a)
 }
 
 // runProgram is the action for running a binary that has already
 // been compiled.  We ignore exit status.
 func (b *builder) runProgram(a *action) error {
@@ skipping 13 matching lines @@
         cmdline := stringList(cmdargs...)
         cmd := exec.Command(cmdline[0], cmdline[1:]...)
         cmd.Stdin = os.Stdin
         cmd.Stdout = os.Stdout
         cmd.Stderr = os.Stderr
         startSigHandlers()
         if err := cmd.Run(); err != nil {
                 errorf("%v", err)
         }
 }