[llvm] [llvm][Support] Add support for executing a detached process (PR #81708)

[Alexandre Ganea via llvm-commits]

================
@@ -260,6 +260,79 @@ TEST_F(ProgramEnvTest, TestExecuteNoWait) {
   ASSERT_GT(LoopCount, 1u) << "LoopCount should be >1";
 }
 
+TEST_F(ProgramEnvTest, TestExecuteNoWaitDetached) {
+  using namespace llvm::sys;
+
+  if (getenv("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT_DETACHED")) {
+    sleep_for(/*seconds=*/5);
+
+#if _WIN32
+    HWND ConsoleWnd = GetConsoleWindow();
+    if (ConsoleWnd == NULL)
+      exit(100);
+    else
+      exit(200);
+#else
+    int ParentSID = std::stoi(
+        std::string(getenv("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT_DETACHED_SID")));
+
+    pid_t ChildSID = ::getsid(0);
+    if (ChildSID == -1) {
+      llvm::errs() << "Could not get process SID: " << strerror(errno) << '\n';
+      exit(1);
+    }
+
+    char *Detached = getenv("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT_DETACHED_TRUE");
+    if (Detached && (ChildSID != ParentSID))
+      exit(100);
+    if (!Detached && (ChildSID == ParentSID))
+      exit(200);
+#endif
+    exit(0);
+  }
+
+  std::string Executable =
+      sys::fs::getMainExecutable(TestMainArgv0, &ProgramTestStringArg1);
+  StringRef argv[] = {
+      Executable, "--gtest_filter=ProgramEnvTest.TestExecuteNoWaitDetached"};
+  addEnvVar("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT_DETACHED=1");
+
+#ifndef _WIN32
+  pid_t SID = ::getsid(0);
+  ASSERT_NE(SID, -1);
+  std::string SIDEnvVar =
+      "LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT_DETACHED_SID=" + std::to_string(SID);
+  addEnvVar(SIDEnvVar);
+#endif
+
+  // DetachProcess = true
+  {
+    std::string Error;
+    bool ExecutionFailed;
+    std::vector<llvm::StringRef> Env = getEnviron();
+    Env.emplace_back("LLVM_PROGRAM_TEST_EXECUTE_NO_WAIT_DETACHED_TRUE=1");
+    ProcessInfo PI1 =
+        ExecuteNoWait(Executable, argv, Env, {}, 0, &Error, &ExecutionFailed,
+                      nullptr, /*DetachedProcess=*/true);
+    ASSERT_FALSE(ExecutionFailed) << Error;
+    ASSERT_NE(PI1.Pid, ProcessInfo::InvalidPid) << "Invalid process id";
+    ProcessInfo WaitResult = Wait(PI1, std::nullopt, &Error);
+    ASSERT_EQ(WaitResult.ReturnCode, 100);
+  }
+
+  // DetachProcess = false
+  {
+    std::string Error;
+    bool ExecutionFailed;
+    ProcessInfo PI2 = ExecuteNoWait(Executable, argv, getEnviron(), {}, 0,
+                                    &Error, &ExecutionFailed, nullptr);
----------------
aganea wrote:

I would add `, /*DetachedProcess=*/false` to make it explicit what we're testing, and not rely on a default value elsewhere.

https://github.com/llvm/llvm-project/pull/81708