Add non-blocking Wait() for launched processes

- New ProcessInfo class to encapsulate information about child processes.
- Generalized the Wait() to support non-blocking wait on child processes.
- ExecuteNoWait() now returns a ProcessInfo object with information about
  the launched child. Users will be able to use this object to
  perform non-blocking wait.
- ExecuteNoWait() now accepts an ExecutionFailed param that tells if execution
  failed or not.

These changes will allow users to implement basic process parallel
tools.

Differential Revision: http://llvm-reviews.chandlerc.com/D1728


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191763 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/Support/ProgramTest.cpp

@@ -21,6 +21,20 @@
 extern char **environ;
 #endif
 
+#if defined(LLVM_ON_UNIX)
+#include <unistd.h>
+void sleep_for(unsigned int seconds) {
+  sleep(seconds);
+}
+#elif defined(LLVM_ON_WIN32)
+#include <windows.h>
+void sleep_for(unsigned int seconds) {
+  Sleep(seconds * 1000);
+}
+#else
+#error sleep_for is not implemented on your platform.
+#endif
+
 // From TestMain.cpp.
 extern const char *TestMainArgv0;
 
@@ -88,4 +102,93 @@ TEST(ProgramTest, CreateProcessTrailingSlash) {
   EXPECT_EQ(0, rc);
 }
 
+TEST(ProgramTest, TestExecuteNoWait) {
+  using namespace llvm::sys;
+
+  if (getenv("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT")) {
+    sleep_for(/*seconds*/ 1);
+    exit(0);
+  }
+
+  std::string Executable =
+      sys::fs::getMainExecutable(TestMainArgv0, &ProgramTestStringArg1);
+  const char *argv[] = {
+    Executable.c_str(),
+    "--gtest_filter=ProgramTest.TestExecuteNoWait",
+    0
+  };
+
+  // Add LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT to the environment of the child.
+  std::vector<const char *> envp;
+  CopyEnvironment(envp);
+  envp.push_back("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT=1");
+  envp.push_back(0);
+
+  std::string Error;
+  bool ExecutionFailed;
+  ProcessInfo PI1 =
+      ExecuteNoWait(Executable, argv, &envp[0], 0, 0, &Error, &ExecutionFailed);
+  ASSERT_FALSE(ExecutionFailed) << Error;
+  ASSERT_NE(PI1.Pid, 0) << "Invalid process id";
+
+  unsigned LoopCount = 0;
+
+  // Test that Wait() with WaitUntilTerminates=true works. In this case,
+  // LoopCount should only be incremented once.
+  while (true) {
+    ++LoopCount;
+    ProcessInfo WaitResult = Wait(PI1, 0, true, &Error);
+    ASSERT_TRUE(Error.empty());
+    if (WaitResult.Pid == PI1.Pid)
+      break;
+  }
+
+  EXPECT_EQ(LoopCount, 1u) << "LoopCount should be 1";
+
+  ProcessInfo PI2 =
+      ExecuteNoWait(Executable, argv, &envp[0], 0, 0, &Error, &ExecutionFailed);
+  ASSERT_FALSE(ExecutionFailed) << Error;
+  ASSERT_NE(PI2.Pid, 0) << "Invalid process id";
+
+  // Test that Wait() with SecondsToWait=0 performs a non-blocking wait. In this
+  // cse, LoopCount should be greater than 1 (more than one increment occurs).
+  while (true) {
+    ++LoopCount;
+    ProcessInfo WaitResult = Wait(PI2, 0, false, &Error);
+    ASSERT_TRUE(Error.empty());
+    if (WaitResult.Pid == PI2.Pid)
+      break;
+  }
+
+  ASSERT_GT(LoopCount, 1u) << "LoopCount should be >1";
+}
+
+TEST(ProgramTest, TestExecuteNegative) {
+  std::string Executable = "i_dont_exist";
+  const char *argv[] = { Executable.c_str(), 0 };
+
+  {
+    std::string Error;
+    bool ExecutionFailed;
+    int RetCode =
+        ExecuteAndWait(Executable, argv, 0, 0, 0, 0, &Error, &ExecutionFailed);
+    ASSERT_TRUE(RetCode < 0) << "On error ExecuteAndWait should return 0 or "
+                                "positive value indicating the result code";
+    ASSERT_TRUE(ExecutionFailed);
+    ASSERT_FALSE(Error.empty());
+  }
+
+  {
+    std::string Error;
+    bool ExecutionFailed;
+    ProcessInfo PI =
+        ExecuteNoWait(Executable, argv, 0, 0, 0, &Error, &ExecutionFailed);
+    ASSERT_EQ(PI.Pid, 0)
+        << "On error ExecuteNoWait should return an invalid ProcessInfo";
+    ASSERT_TRUE(ExecutionFailed);
+    ASSERT_FALSE(Error.empty());
+  }
+
+}
+
 } // end anonymous namespace