libutil: return Pid from startProcess, not pid_t

Change-Id: Icc8a15090c77f54ea7d9220aadedcd4a19922814

src/libmain/shared.cc

@@ -354,7 +354,7 @@ RunPager::RunPager()
     Pipe toPager;
     toPager.create();
 
-    pid = Pid{startProcess([&]() {
+    pid = startProcess([&]() {
         if (dup2(toPager.readSide.get(), STDIN_FILENO) == -1)
             throw SysError("dupping stdin");
         if (!getenv("LESS"))
@@ -366,7 +366,7 @@ RunPager::RunPager()
         execlp("less", "less", nullptr);
         execlp("more", "more", nullptr);
         throw SysError("executing '%1%'", pager);
-    })};
+    });
 
     pid.setKillSignal(SIGINT);
     std_out = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 0);

src/libstore/build/hook-instance.cc

@@ -35,7 +35,7 @@ HookInstance::HookInstance()
     builderOut.create();
 
     /* Fork the hook. */
-    pid = Pid{startProcess([&]() {
+    pid = startProcess([&]() {
 
         if (dup2(fromHook.writeSide.get(), STDERR_FILENO) == -1)
             throw SysError("cannot pipe standard error into log file");
@@ -60,7 +60,7 @@ HookInstance::HookInstance()
         execv(buildHook.c_str(), stringsToCharPtrs(args).data());
 
         throw SysError("executing '%s'", buildHook);
-    })};
+    });
 
     pid.setSeparatePG(true);
     fromHook.writeSide.reset();

src/libstore/build/local-derivation-goal.cc

@@ -906,7 +906,7 @@ void LocalDerivationGoal::startBuilder()
         Pipe sendPid;
         sendPid.create();
 
-        Pid helper{startProcess([&]() {
+        Pid helper = startProcess([&]() {
             sendPid.readSide.close();
 
             /* We need to open the slave early, before
@@ -930,11 +930,11 @@ void LocalDerivationGoal::startBuilder()
             if (usingUserNamespace)
                 options.cloneFlags |= CLONE_NEWUSER;
 
-            pid_t child = startProcess([&]() { runChild(); }, options);
+            pid_t child = startProcess([&]() { runChild(); }, options).release();
 
             writeFull(sendPid.writeSide.get(), fmt("%d\n", child));
             _exit(0);
-        })};
+        });
 
         sendPid.writeSide.close();
 
@@ -1010,10 +1010,10 @@ void LocalDerivationGoal::startBuilder()
     } else
 #endif
     {
-        pid = Pid{startProcess([&]() {
+        pid = startProcess([&]() {
             openSlave();
             runChild();
-        })};
+        });
     }
 
     /* parent */
@@ -1570,7 +1570,7 @@ void LocalDerivationGoal::addDependency(const StorePath & path)
                entering its mount namespace, which is not possible
                in multithreaded programs. So we do this in a
                child process.*/
-            Pid child(startProcess([&]() {
+            Pid child = startProcess([&]() {
 
                 if (usingUserNamespace && (setns(sandboxUserNamespace.get(), 0) == -1))
                     throw SysError("entering sandbox user namespace");
@@ -1581,7 +1581,7 @@ void LocalDerivationGoal::addDependency(const StorePath & path)
                 doBind(source, target);
 
                 _exit(0);
-            }));
+            });
 
             int status = child.wait();
             if (status != 0)

src/libstore/ssh.cc

@@ -70,7 +70,7 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string
     }
     Finally cleanup = [&]() { logger->resume(); };
 
-    conn->sshPid = Pid{startProcess([&]() {
+    conn->sshPid = startProcess([&]() {
         restoreProcessContext();
 
         close(in.writeSide.get());
@@ -99,7 +99,7 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string
 
         // could not exec ssh/bash
         throw SysError("unable to execute '%s'", args.front());
-    }, options)};
+    }, options);
 
 
     in.readSide.reset();
@@ -147,7 +147,7 @@ Path SSHMaster::startMaster()
     if (isMasterRunning())
         return state->socketPath;
 
-    state->sshMaster = Pid{startProcess([&]() {
+    state->sshMaster = startProcess([&]() {
         restoreProcessContext();
 
         close(out.readSide.get());
@@ -160,7 +160,7 @@ Path SSHMaster::startMaster()
         execvp(args.begin()->c_str(), stringsToCharPtrs(args).data());
 
         throw SysError("unable to execute '%s'", args.front());
-    }, options)};
+    }, options);
 
     out.writeSide.reset();
 

src/libutil/namespaces.cc

@@ -94,7 +94,7 @@ bool userNamespacesSupported()
     static auto res = [&]() -> bool
     {
         try {
-            Pid pid{startProcess([&]() { _exit(0); }, {.cloneFlags = CLONE_NEWUSER})};
+            Pid pid = startProcess([&]() { _exit(0); }, {.cloneFlags = CLONE_NEWUSER});
 
             auto r = pid.wait();
             assert(!r);
@@ -115,7 +115,7 @@ bool mountAndPidNamespacesSupported()
     {
         try {
 
-            Pid pid{startProcess([&]() {
+            Pid pid = startProcess([&]() {
                 /* Make sure we don't remount the parent's /proc. */
                 if (mount(0, "/", 0, MS_PRIVATE | MS_REC, 0) == -1)
                     _exit(1);
@@ -130,7 +130,7 @@ bool mountAndPidNamespacesSupported()
                 _exit(0);
             }, {
                 .cloneFlags = CLONE_NEWNS | CLONE_NEWPID | (userNamespacesSupported() ? CLONE_NEWUSER : 0)
-            })};
+            });
 
             if (pid.wait()) {
                 debug("PID namespaces do not work on this system: cannot remount /proc");

src/libutil/processes.cc

@@ -183,7 +183,7 @@ static int childEntry(void * arg)
 #endif
 
 
-pid_t startProcess(std::function<void()> fun, const ProcessOptions & options)
+Pid startProcess(std::function<void()> fun, const ProcessOptions & options)
 {
     std::function<void()> wrapper = [&]() {
         logger = makeSimpleLogger();
@@ -227,7 +227,7 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options)
 
     if (pid == -1) throw SysError("unable to fork");
 
-    return pid;
+    return Pid{pid};
 }
 
 std::string runProgram(Path program, bool searchPath, const Strings & args,

src/libutil/processes.hh

@@ -62,7 +62,8 @@ struct ProcessOptions
     int cloneFlags = 0;
 };
 
-pid_t startProcess(std::function<void()> fun, const ProcessOptions & options = ProcessOptions());
+[[nodiscard]]
+Pid startProcess(std::function<void()> fun, const ProcessOptions & options = ProcessOptions());
 
 
 /**

src/nix/daemon.cc

@@ -369,7 +369,7 @@ static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
                 processConnection(openUncachedStore(), from, to, trusted, NotRecursive);
 
                 exit(0);
-            }, options);
+            }, options).release();
 
         } catch (Interrupted & e) {
             return;

tests/functional/repl_characterization/test-session.cc

@@ -22,7 +22,7 @@ RunningProcess RunningProcess::start(std::string executable, Strings args)
     procStdout.create();
 
     // This is separate from runProgram2 because we have different IO requirements
-    pid_t pid = startProcess([&]() {
+    auto pid = startProcess([&]() {
         if (dup2(procStdout.writeSide.get(), STDOUT_FILENO) == -1) {
             throw SysError("dupping stdout");
         }
@@ -42,7 +42,7 @@ RunningProcess RunningProcess::start(std::string executable, Strings args)
     procStdin.readSide.close();
 
     return RunningProcess{
-        .pid = pid,
+        .pid = std::move(pid),
         .procStdin = std::move(procStdin),
         .procStdout = std::move(procStdout),
     };

tests/functional/repl_characterization/test-session.hh

@@ -7,13 +7,14 @@
 #include <string>
 
 #include "file-descriptor.hh"
+#include "processes.hh"
 #include "tests/terminal-code-eater.hh"
 
 namespace nix {
 
 struct RunningProcess
 {
-    pid_t pid;
+    Pid pid;
     Pipe procStdin;
     Pipe procStdout;