cmd/compile: fix TestAssembly on Plan 9

Since CL 23620, TestAssembly is failing on Plan 9.

In CL 23620, the process environment is passed to 'go tool compile'
after setting GOARCH. On Plan 9, if GOARCH is already set in the
process environment, it would take precedence. On Unix, it works
as expected because the first GOARCH found takes precedence.

This change uses the mergeEnvLists function from cmd/go/main.go
to merge the two environment lists such that variables with the
same name in "in" replace those in "out".

Change-Id: Idee22058343932ee18666dda331c562c89c33507
Reviewed-on: https://go-review.googlesource.com/23593
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: David du Colombier <0intro@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/gc/asm_test.go b/src/cmd/compile/internal/gc/asm_test.go
index 73d2e336d225b22ff0fb92500b9f6957aae7fe8d..b44bf77c5daaff2f9d997fa19adbb2d18b703934 100644 (file)
--- a/src/cmd/compile/internal/gc/asm_test.go
+++ b/src/cmd/compile/internal/gc/asm_test.go
@@ -61,7 +61,7 @@ func compileToAsm(dir, arch, pkg string) string {
 
        var stdout, stderr bytes.Buffer
        cmd := exec.Command("go", "tool", "compile", "-S", "-o", filepath.Join(dir, "out.o"), src)
-       cmd.Env = append([]string{"GOARCH=" + arch}, os.Environ()...)
+       cmd.Env = mergeEnvLists([]string{"GOARCH=" + arch}, os.Environ())
        cmd.Stdout = &stdout
        cmd.Stderr = &stderr
        if err := cmd.Run(); err != nil {
@@ -103,3 +103,22 @@ func f(x int) int {
                []string{"\tSHLQ\t\\$5,", "\tLEAQ\t\\(.*\\)\\(.*\\*2\\),"},
        },
 }
+
+// mergeEnvLists merges the two environment lists such that
+// variables with the same name in "in" replace those in "out".
+// This always returns a newly allocated slice.
+func mergeEnvLists(in, out []string) []string {
+       out = append([]string(nil), out...)
+NextVar:
+       for _, inkv := range in {
+               k := strings.SplitAfterN(inkv, "=", 2)[0]
+               for i, outkv := range out {
+                       if strings.HasPrefix(outkv, k) {
+                               out[i] = inkv
+                               continue NextVar
+                       }
+               }
+               out = append(out, inkv)
+       }
+       return out
+}