QProcess/Unix: update the start error messages to be all similar

The user doesn't care if it happened in the parent process or in the
child.

Windows says "Process failed to start: %1" which is a bit nicer, but I'm
not going to update to that.

Change-Id: If974ba44f84ffc236e48fffd4e48457fac21b248
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

src/corelib/io/qprocess_unix.cpp

@@ -189,6 +189,36 @@ static_assert(std::is_trivial_v<ChildError>);
 static_assert(PIPE_BUF >= sizeof(ChildError)); // PIPE_BUF may be bigger
 #endif
 
+// we need an errno value to use to indicate the child process modifier threw,
+// something the regular operations shouldn't set.
+static constexpr int FakeErrnoForThrow = std::numeric_limits<int>::max();
+
+static QString errorMessageForSyscall(QUtf8StringView fnName, int errnoCode = -1)
+{
+    QString msg = qt_error_string(errnoCode);
+    return QProcess::tr("Child process set up failed: %1: %2").arg(fnName, std::move(msg));
+}
+
+static QString startFailureErrorMessage(ChildError &err, [[maybe_unused]] ssize_t bytesRead)
+{
+    // ChildError is less than the POSIX pipe buffer atomic size, so the read
+    // must not have been truncated
+    Q_ASSERT(bytesRead == sizeof(err));
+
+    qsizetype len = qstrnlen(err.function, sizeof(err.function));
+    const QUtf8StringView complement(err.function, len);
+    if (err.code == FakeErrnoForThrow)
+        return QProcess::tr("Child process modifier threw an exception: %1")
+                .arg(complement);
+    if (err.code == 0)
+        return QProcess::tr("Child process modifier reported error: %1")
+                .arg(complement);
+    if (err.code < 0)
+        return QProcess::tr("Child process modifier reported error: %1: %2")
+                .arg(complement, qt_error_string(-err.code));
+    return errorMessageForSyscall(complement, err.code);
+}
+
 struct QProcessPoller
 {
     QProcessPoller(const QProcessPrivate &proc);
@@ -262,7 +292,7 @@ struct QChildProcess
         if (!d->workingDirectory.isEmpty()) {
             workingDirectory = opendirfd(QFile::encodeName(d->workingDirectory));
             if (workingDirectory < 0) {
-                d->setErrorAndEmit(QProcess::FailedToStart, "chdir: "_L1 + qt_error_string());
+                d->setErrorAndEmit(QProcess::FailedToStart, errorMessageForSyscall("chdir"));
                 d->cleanup();
 
                 // make sure our destructor does nothing
@@ -491,7 +521,7 @@ bool QProcessPrivate::openChannel(Channel &channel)
     if (channel.type == Channel::Normal) {
         // we're piping this channel to our own process
         if (qt_create_pipe(channel.pipe) != 0) {
-            setErrorAndEmit(QProcess::FailedToStart, "pipe: "_L1 + qt_error_string(errno));
+            setErrorAndEmit(QProcess::FailedToStart, errorMessageForSyscall("pipe"));
             return false;
         }
 
@@ -573,7 +603,7 @@ bool QProcessPrivate::openChannel(Channel &channel)
 
             Q_PIPE pipe[2] = { -1, -1 };
             if (qt_create_pipe(pipe) != 0) {
-                setErrorAndEmit(QProcess::FailedToStart, "pipe: "_L1 + qt_error_string(errno));
+                setErrorAndEmit(QProcess::FailedToStart, errorMessageForSyscall("pipe"));
                 return false;
             }
             sink->pipe[0] = pipe[0];
@@ -708,7 +738,7 @@ void QProcessPrivate::startProcess()
         return;
     }
     if (qt_create_pipe(childStartedPipe) != 0) {
-        setErrorAndEmit(QProcess::FailedToStart, "pipe: "_L1 + qt_error_string(errno));
+        setErrorAndEmit(QProcess::FailedToStart, errorMessageForSyscall("pipe"));
         cleanup();
         return;
     }
@@ -778,31 +808,6 @@ void QProcessPrivate::startProcess()
         ::fcntl(stderrChannel.pipe[0], F_SETFL, ::fcntl(stderrChannel.pipe[0], F_GETFL) | O_NONBLOCK);
 }
 
-// we need an errno number to use to indicate the child process modifier threw,
-// something the regular operations shouldn't set.
-static constexpr int FakeErrnoForThrow = std::numeric_limits<int>::max();
-
-static QString startFailureErrorMessage(ChildError &err, [[maybe_unused]] ssize_t bytesRead)
-{
-    // ChildError is less than the POSIX pipe buffer atomic size, so the read
-    // must not have been truncated
-    Q_ASSERT(bytesRead == sizeof(err));
-
-    qsizetype len = qstrnlen(err.function, sizeof(err.function));
-    const QUtf8StringView complement(err.function, len);
-    if (err.code == FakeErrnoForThrow)
-        return QProcess::tr("Child process modifier threw an exception: %1")
-                .arg(complement);
-    if (err.code == 0)
-        return QProcess::tr("Child process modifier reported error: %1")
-                .arg(complement);
-    if (err.code < 0)
-        return QProcess::tr("Child process modifier reported error: %1: %2")
-                .arg(complement, qt_error_string(-err.code));
-    return QProcess::tr("Child process set up failed: %1: %2")
-            .arg(complement, qt_error_string(err.code));
-}
-
 Q_NORETURN void
 failChildProcess(const QProcessPrivate *d, const char *description, int code) noexcept
 {
@@ -1320,7 +1325,7 @@ bool QProcessPrivate::startDetached(qint64 *pid)
 {
     AutoPipe startedPipe, pidPipe;
     if (!startedPipe || !pidPipe) {
-        setErrorAndEmit(QProcess::FailedToStart, "pipe: "_L1 + qt_error_string(errno));
+        setErrorAndEmit(QProcess::FailedToStart, errorMessageForSyscall("pipe"));
         return false;
     }
 
@@ -1359,7 +1364,7 @@ bool QProcessPrivate::startDetached(qint64 *pid)
 
     if (childPid == -1) {
         childProcess.cleanup();
-        setErrorAndEmit(QProcess::FailedToStart, "fork: "_L1 + qt_error_string(savedErrno));
+        setErrorAndEmit(QProcess::FailedToStart, errorMessageForSyscall("fork", savedErrno));
         return false;
     }
 

tests/auto/corelib/io/qprocess/tst_qprocess.cpp

@@ -2884,7 +2884,8 @@ void tst_QProcess::detachedSetNonExistentWorkingDirectory()
     QCOMPARE(process.error(), QProcess::FailedToStart);
 
 #ifdef Q_OS_UNIX
-    QVERIFY2(process.errorString().startsWith("chdir:"), process.errorString().toLocal8Bit());
+    QVERIFY2(process.errorString().contains(": chdir: "), process.errorString().toLocal8Bit());
+    QVERIFY2(process.errorString().contains(qt_error_string(ENOENT)), process.errorString().toLocal8Bit());
 #endif
 }