cmd/cgo: do not use gcc -xc - to compile standard input

We have private reports of compilers that mishandle that.
Write to a temporary file instead.

Change-Id: I92e3cf4274b1a8048741e07fb52b8900c93b915e
Reviewed-on: https://go-review.googlesource.com/19616
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/cgo/util.go b/src/cmd/cgo/util.go
index 3adb8e87836c21adc289b70711ebfbb326370b81..52ca160ad9be8890974698ddd449581e9861c7d3 100644 (file)
--- a/src/cmd/cgo/util.go
+++ b/src/cmd/cgo/util.go
@@ -8,6 +8,7 @@ import (
        "bytes"
        "fmt"
        "go/token"
+       "io/ioutil"
        "os"
        "os/exec"
 )
@@ -16,6 +17,43 @@ import (
 // It returns the output to standard output and standard error.
 // ok indicates whether the command exited successfully.
 func run(stdin []byte, argv []string) (stdout, stderr []byte, ok bool) {
+       if i := find(argv, "-xc"); i >= 0 && argv[len(argv)-1] == "-" {
+               // Some compilers have trouble with standard input.
+               // Others have trouble with -xc.
+               // Avoid both problems by writing a file with a .c extension.
+               f, err := ioutil.TempFile("", "cgo-gcc-input-")
+               if err != nil {
+                       fatalf("%s", err)
+               }
+               name := f.Name()
+               f.Close()
+               if err := ioutil.WriteFile(name+".c", stdin, 0666); err != nil {
+                       os.Remove(name)
+                       fatalf("%s", err)
+               }
+               defer os.Remove(name)
+               defer os.Remove(name + ".c")
+
+               // Build new argument list without -xc and trailing -.
+               new := append(argv[:i:i], argv[i+1:len(argv)-1]...)
+
+               // Since we are going to write the file to a temporary directory,
+               // we will need to add -I . explicitly to the command line:
+               // any #include "foo" before would have looked in the current
+               // directory as the directory "holding" standard input, but now
+               // the temporary directory holds the input.
+               // We've also run into compilers that reject "-I." but allow "-I", ".",
+               // so be sure to use two arguments.
+               // This matters mainly for people invoking cgo -godefs by hand.
+               new = append(new, "-I", ".")
+
+               // Finish argument list with path to C file.
+               new = append(new, name+".c")
+
+               argv = new
+               stdin = nil
+       }
+
        p := exec.Command(argv[0], argv[1:]...)
        p.Stdin = bytes.NewReader(stdin)
        var bout, berr bytes.Buffer
@@ -30,6 +68,15 @@ func run(stdin []byte, argv []string) (stdout, stderr []byte, ok bool) {
        return
 }
 
+func find(argv []string, target string) int {
+       for i, arg := range argv {
+               if arg == target {
+                       return i
+               }
+       }
+       return -1
+}
+
 func lineno(pos token.Pos) string {
        return fset.Position(pos).String()
 }