Look up executable on PATH when given environment variables.

runtime/bin/process_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/process.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
 #include "bin/fdutils.h"
 #include "bin/thread.h"
 
+extern char **environ;
 
 // ProcessInfo is used to map a process id to the file descriptor for
 // the pipe used to communicate the exit code of the process to Dart.
 // ProcessInfo objects are kept in the static singly-linked
 // ProcessInfoList.
 class ProcessInfo {
  public:
   ProcessInfo(pid_t pid, intptr_t fd) : pid_(pid), fd_(fd) { }
   ~ProcessInfo() {
     int closed = TEMP_FAILURE_RETRY(close(fd_));
@@ skipping 424 matching lines @@
     if (TEMP_FAILURE_RETRY(dup2(read_err[1], STDERR_FILENO)) == -1) {
       ReportChildError(exec_control[1]);
     }
     TEMP_FAILURE_RETRY(close(read_err[1]));
 
     if (working_directory != NULL &&
         TEMP_FAILURE_RETRY(chdir(working_directory)) == -1) {
       ReportChildError(exec_control[1]);
     }
 
-    if (environment != NULL) {
-      TEMP_FAILURE_RETRY(
-          execve(path,
-                 const_cast<char* const*>(program_arguments),
-                 program_environment));
-    } else {
-      TEMP_FAILURE_RETRY(
-          execvp(path, const_cast<char* const*>(program_arguments)));
+    char **orig_environ = environ;
+    if (program_environment != NULL) {
+      environ = program_environment;
     }
+    TEMP_FAILURE_RETRY(
+        execvp(path, const_cast<char* const*>(program_arguments)));
+    // Dead code, unless execvp fails.
+    environ = orig_environ;
+
     ReportChildError(exec_control[1]);
   }
 
   // The arguments and environment for the spawned process are not needed
   // any longer.
   delete[] program_arguments;
   delete[] program_environment;
 
   int event_fds[2];
   result = TEMP_FAILURE_RETRY(pipe(event_fds));
@@ skipping 74 matching lines @@
 
 
 void Process::TerminateExitCodeHandler() {
   ExitCodeHandler::TerminateExitCodeThread();
 }
 
 
 intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(getpid());
 }