Fix "unexpected EOF" errors on macOS

mk/run-test.sh

@@ -27,18 +27,6 @@ run_test () {
 
 run_test
 
-# Hack: Retry the test if it fails with “unexpected EOF reading a line” as these
-# appear randomly without anyone knowing why.
-# See https://github.com/NixOS/nix/issues/3605 for more info
-if [[ $status -ne 0 && $status -ne 99 && \
-    "$(uname)" == "Darwin" && \
-    "$log" =~ "unexpected EOF reading a line" \
-]]; then
-    echo "$post_run_msg [${yellow}FAIL$normal] (possibly flaky, so will be retried)"
-    echo "$log" | sed 's/^/    /'
-    run_test
-fi
-
 if [ $status -eq 0 ]; then
   echo "$post_run_msg [${green}PASS$normal]"
 elif [ $status -eq 99 ]; then

src/libstore/build/hook-instance.cc

@@ -35,7 +35,7 @@ HookInstance::HookInstance()
     /* Fork the hook. */
     pid = startProcess([&]() {
 
-        commonChildInit(fromHook);
+        commonChildInit(fromHook.writeSide.get());
 
         if (chdir("/") == -1) throw SysError("changing into /");
 

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

@@ -292,7 +292,7 @@ void LocalDerivationGoal::closeReadPipes()
     if (hook) {
         DerivationGoal::closeReadPipes();
     } else
-        builderOut.readSide = -1;
+        builderOut.close();
 }
 
 
@@ -802,15 +802,13 @@ void LocalDerivationGoal::startBuilder()
     /* Create the log file. */
     Path logFile = openLogFile();
 
-    /* Create a pipe to get the output of the builder. */
-    //builderOut.create();
-
-    builderOut.readSide = posix_openpt(O_RDWR | O_NOCTTY);
-    if (!builderOut.readSide)
+    /* Create a pseudoterminal to get the output of the builder. */
+    builderOut = posix_openpt(O_RDWR | O_NOCTTY);
+    if (!builderOut)
         throw SysError("opening pseudoterminal master");
 
     // FIXME: not thread-safe, use ptsname_r
-    std::string slaveName(ptsname(builderOut.readSide.get()));
+    std::string slaveName = ptsname(builderOut.get());
 
     if (buildUser) {
         if (chmod(slaveName.c_str(), 0600))
@@ -821,35 +819,14 @@ void LocalDerivationGoal::startBuilder()
     }
 #if __APPLE__
     else {
-        if (grantpt(builderOut.readSide.get()))
+        if (grantpt(builderOut.get()))
             throw SysError("granting access to pseudoterminal slave");
     }
 #endif
 
-    #if 0
-    // Mount the pt in the sandbox so that the "tty" command works.
-    // FIXME: this doesn't work with the new devpts in the sandbox.
-    if (useChroot)
-        dirsInChroot[slaveName] = {slaveName, false};
-    #endif
-
-    if (unlockpt(builderOut.readSide.get()))
+    if (unlockpt(builderOut.get()))
         throw SysError("unlocking pseudoterminal");
 
-    builderOut.writeSide = open(slaveName.c_str(), O_RDWR | O_NOCTTY);
-    if (!builderOut.writeSide)
-        throw SysError("opening pseudoterminal slave");
-
-    // Put the pt into raw mode to prevent \n -> \r\n translation.
-    struct termios term;
-    if (tcgetattr(builderOut.writeSide.get(), &term))
-        throw SysError("getting pseudoterminal attributes");
-
-    cfmakeraw(&term);
-
-    if (tcsetattr(builderOut.writeSide.get(), TCSANOW, &term))
-        throw SysError("putting pseudoterminal into raw mode");
-
     buildResult.startTime = time(0);
 
     /* Fork a child to build the package. */
@@ -897,7 +874,11 @@ void LocalDerivationGoal::startBuilder()
 
         usingUserNamespace = userNamespacesSupported();
 
+        Pipe sendPid;
+        sendPid.create();
+
         Pid helper = startProcess([&]() {
+            sendPid.readSide.close();
 
             /* Drop additional groups here because we can't do it
                after we've created the new user namespace.  FIXME:
@@ -917,13 +898,14 @@ void LocalDerivationGoal::startBuilder()
             if (usingUserNamespace)
                 options.cloneFlags |= CLONE_NEWUSER;
 
-            pid_t child = startProcess([&]() { runChild(); }, options);
+            pid_t child = startProcess([&]() { runChild(slaveName); }, options);
 
-            writeFull(builderOut.writeSide.get(),
-                fmt("%d %d\n", usingUserNamespace, child));
+            writeFull(sendPid.writeSide.get(), fmt("%d\n", child));
             _exit(0);
         });
 
+        sendPid.writeSide.close();
+
         if (helper.wait() != 0)
             throw Error("unable to start build process");
 
@@ -935,10 +917,9 @@ void LocalDerivationGoal::startBuilder()
             userNamespaceSync.writeSide = -1;
         });
 
-        auto ss = tokenizeString<std::vector<std::string>>(readLine(builderOut.readSide.get()));
-        assert(ss.size() == 2);
-        usingUserNamespace = ss[0] == "1";
-        pid = string2Int<pid_t>(ss[1]).value();
+        auto ss = tokenizeString<std::vector<std::string>>(readLine(sendPid.readSide.get()));
+        assert(ss.size() == 1);
+        pid = string2Int<pid_t>(ss[0]).value();
 
         if (usingUserNamespace) {
             /* Set the UID/GID mapping of the builder's user namespace
@@ -993,21 +974,20 @@ void LocalDerivationGoal::startBuilder()
 #endif
     {
         pid = startProcess([&]() {
-            runChild();
+            runChild(slaveName);
         });
     }
 
     /* parent */
     pid.setSeparatePG(true);
-    builderOut.writeSide = -1;
-    worker.childStarted(shared_from_this(), {builderOut.readSide.get()}, true, true);
+    worker.childStarted(shared_from_this(), {builderOut.get()}, true, true);
 
     /* Check if setting up the build environment failed. */
     std::vector<std::string> msgs;
     while (true) {
         std::string msg = [&]() {
             try {
-                return readLine(builderOut.readSide.get());
+                return readLine(builderOut.get());
             } catch (Error & e) {
                 auto status = pid.wait();
                 e.addTrace({}, "while waiting for the build environment for '%s' to initialize (%s, previous messages: %s)",
@@ -1019,7 +999,7 @@ void LocalDerivationGoal::startBuilder()
         }();
         if (msg.substr(0, 1) == "\2") break;
         if (msg.substr(0, 1) == "\1") {
-            FdSource source(builderOut.readSide.get());
+            FdSource source(builderOut.get());
             auto ex = readError(source);
             ex.addTrace({}, "while setting up the build environment");
             throw ex;
@@ -1640,7 +1620,7 @@ void setupSeccomp()
 }
 
 
-void LocalDerivationGoal::runChild()
+void LocalDerivationGoal::runChild(const Path & slaveName)
 {
     /* Warning: in the child we should absolutely not make any SQLite
        calls! */
@@ -1649,7 +1629,22 @@ void LocalDerivationGoal::runChild()
 
     try { /* child */
 
-        commonChildInit(builderOut);
+        /* Open the slave side of the pseudoterminal. */
+        AutoCloseFD builderOut = open(slaveName.c_str(), O_RDWR | O_NOCTTY);
+        if (!builderOut)
+            throw SysError("opening pseudoterminal slave");
+
+        // Put the pt into raw mode to prevent \n -> \r\n translation.
+        struct termios term;
+        if (tcgetattr(builderOut.get(), &term))
+            throw SysError("getting pseudoterminal attributes");
+
+        cfmakeraw(&term);
+
+        if (tcsetattr(builderOut.get(), TCSANOW, &term))
+            throw SysError("putting pseudoterminal into raw mode");
+
+        commonChildInit(builderOut.get());
 
         try {
             setupSeccomp();
@@ -2891,7 +2886,7 @@ void LocalDerivationGoal::deleteTmpDir(bool force)
 bool LocalDerivationGoal::isReadDesc(int fd)
 {
     return (hook && DerivationGoal::isReadDesc(fd)) ||
-        (!hook && fd == builderOut.readSide.get());
+        (!hook && fd == builderOut.get());
 }
 
 

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

@@ -24,8 +24,9 @@ struct LocalDerivationGoal : public DerivationGoal
     /* The path of the temporary directory in the sandbox. */
     Path tmpDirInSandbox;
 
-    /* Pipe for the builder's standard output/error. */
-    Pipe builderOut;
+    /* Master side of the pseudoterminal used for the builder's
+       standard output/error. */
+    AutoCloseFD builderOut;
 
     /* Pipe for synchronising updates to the builder namespaces. */
     Pipe userNamespaceSync;
@@ -168,7 +169,7 @@ struct LocalDerivationGoal : public DerivationGoal
     int getChildStatus() override;
 
     /* Run the builder's process. */
-    void runChild();
+    void runChild(const std::string & slaveName);
 
     /* Check that the derivation outputs all exist and register them
        as valid. */

src/libutil/util.cc

@@ -1968,7 +1968,7 @@ std::string showBytes(uint64_t bytes)
 
 
 // FIXME: move to libstore/build
-void commonChildInit(Pipe & logPipe)
+void commonChildInit(int stderrFd)
 {
     logger = makeSimpleLogger();
 
@@ -1983,7 +1983,7 @@ void commonChildInit(Pipe & logPipe)
         throw SysError("creating a new session");
 
     /* Dup the write side of the logger pipe into stderr. */
-    if (dup2(logPipe.writeSide.get(), STDERR_FILENO) == -1)
+    if (dup2(stderrFd, STDERR_FILENO) == -1)
         throw SysError("cannot pipe standard error into log file");
 
     /* Dup stderr to stdout. */

src/libutil/util.hh

@@ -704,7 +704,7 @@ typedef std::function<bool(const Path & path)> PathFilter;
 extern PathFilter defaultPathFilter;
 
 /* Common initialisation performed in child processes. */
-void commonChildInit(Pipe & logPipe);
+void commonChildInit(int stderrFd);
 
 /* Create a Unix domain socket. */
 AutoCloseFD createUnixDomainSocket();