From a19feeb31b3e39caccb8f6d275664fc6baf2c894 Mon Sep 17 00:00:00 2001
From: Benny Scetbun <benny@zen.ly>
Date: Fri, 15 Jun 2018 19:02:44 +0200
Subject: [PATCH] turn relative path to absolute path in environment's cgo's
 flags

---
 go/tools/builders/asm.go     |  2 +-
 go/tools/builders/compile.go |  2 +-
 go/tools/builders/env.go     | 46 ++++++++++++++++++++++--------------
 go/tools/builders/stdlib.go  |  6 +++++
 4 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/go/tools/builders/asm.go b/go/tools/builders/asm.go
index b3a2a71bec..1370fc3a40 100644
--- a/go/tools/builders/asm.go
+++ b/go/tools/builders/asm.go
@@ -52,7 +52,7 @@ func run(args []string) error {
 	// Build source with the assembler.
 	goargs := goenv.goTool("asm", toolArgs...)
 	goargs = append(goargs, source)
-	absArgs(goargs, []string{"I", "o", "trimpath"})
+	absArgs(goargs, []string{"-I", "-o", "-trimpath"})
 	return goenv.runCommand(goargs)
 }
 
diff --git a/go/tools/builders/compile.go b/go/tools/builders/compile.go
index 5acce68cae..30c8e2f3c8 100644
--- a/go/tools/builders/compile.go
+++ b/go/tools/builders/compile.go
@@ -118,7 +118,7 @@ func run(args []string) error {
 	for _, f := range files {
 		goargs = append(goargs, f.filename)
 	}
-	absArgs(goargs, []string{"I", "o", "trimpath"})
+	absArgs(goargs, []string{"-I", "-o", "-trimpath"})
 	return goenv.runCommand(goargs)
 }
 
diff --git a/go/tools/builders/env.go b/go/tools/builders/env.go
index b0dd62a3c5..ec1b6a1367 100644
--- a/go/tools/builders/env.go
+++ b/go/tools/builders/env.go
@@ -27,6 +27,13 @@ import (
 	"strings"
 )
 
+var (
+	// cgoEnvVars is the list of all cgo environment variable
+	cgoEnvVars = []string{"CGO_CFLAGS", "CGO_CXXFLAGS", "CGO_CPPFLAGS", "CGO_LDFLAGS"}
+	// cgoAbsEnvFlags are all the flags that need absolute path in cgoEnvVars
+	cgoAbsEnvFlags = []string{"-I", "-L", "-isysroot", "-isystem", "-iquote", "-include", "-gcc-toolchain", "--sysroot"}
+)
+
 // env holds a small amount of Go environment and toolchain information
 // which is common to multiple builders. Most Bazel-agnostic build information
 // is collected in go/build.Default though.
@@ -100,6 +107,17 @@ func (e *env) runCommandToFile(w io.Writer, args []string) error {
 	return runAndLogCommand(cmd, e.verbose)
 }
 
+func absEnv(envNameList []string, argList []string) error {
+	for _, envName := range envNameList {
+		splitedEnv := strings.Fields(os.Getenv(envName))
+		absArgs(splitedEnv, argList)
+		if err := os.Setenv(envName, strings.Join(splitedEnv, " ")); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func runAndLogCommand(cmd *exec.Cmd, verbose bool) error {
 	if verbose {
 		formatCommand(os.Stderr, cmd)
@@ -144,29 +162,21 @@ func absArgs(args []string, flags []string) {
 			absNext = false
 			continue
 		}
-		if !strings.HasPrefix(args[i], "-") {
-			continue
-		}
-		var flag, value string
-		var separate bool
-		if j := strings.IndexByte(args[i], '='); j >= 0 {
-			flag = args[i][:j]
-			value = args[i][j+1:]
-		} else {
-			separate = true
-			flag = args[i]
-		}
-		flag = strings.TrimLeft(args[i], "-")
 		for _, f := range flags {
-			if flag != f {
+			if !strings.HasPrefix(args[i], f) {
 				continue
 			}
-			if separate {
+			possibleValue := args[i][len(f):]
+			if len(possibleValue) == 0 {
 				absNext = true
-			} else {
-				value = abs(value)
-				args[i] = fmt.Sprintf("-%s=%s", flag, value)
+				break
+			}
+			separator := ""
+			if possibleValue[0] == '=' {
+				possibleValue = possibleValue[1:]
+				separator = "="
 			}
+			args[i] = fmt.Sprintf("%s%s%s", f, separator, abs(possibleValue))
 			break
 		}
 	}
diff --git a/go/tools/builders/stdlib.go b/go/tools/builders/stdlib.go
index 53e00142ce..622f06a8fa 100644
--- a/go/tools/builders/stdlib.go
+++ b/go/tools/builders/stdlib.go
@@ -87,6 +87,12 @@ func run(args []string) error {
 	installArgs = append(installArgs, "-ldflags="+allSlug+strings.Join(ldflags, " "))
 	installArgs = append(installArgs, "-asmflags="+allSlug+strings.Join(asmflags, " "))
 
+	// Modifying CGO flags to use only absolute path
+	// because go is having its own sandbox, all CGO flags must use absolute path
+	if err := absEnv(cgoEnvVars, cgoAbsEnvFlags); err != nil {
+		return fmt.Errorf("error modifying cgo environment to absolute path: %v", err)
+	}
+
 	for _, target := range []string{"std", "runtime/cgo"} {
 		if err := goenv.runCommand(append(installArgs, target)); err != nil {
 			return err