Replace a few hardcoded paths with defaults from paths.h

This removes at least one special-case we had to have, in Android's lack
of /etc/mnttab. Bionic's _PATH_MOUNTED is already /proc/mounts.

Change-Id: I9407dcf22de6407c83b5fffd14fedc638586d0f9
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/global/qlogging.cpp

@@ -63,6 +63,9 @@
 #if QT_CONFIG(slog2)
 #include <slog2.h>
 #endif
+#if QT_HAS_INCLUDE(<paths.h>)
+#include <paths.h>
+#endif
 
 #ifdef Q_OS_ANDROID
 #include <android/log.h>
@@ -215,8 +218,11 @@ static bool willLogToConsole()
 #  ifdef Q_OS_WIN
     return GetConsoleWindow();
 #  elif defined(Q_OS_UNIX)
+#    ifndef _PATH_TTY
+#    define _PATH_TTY "/dev/tty"
+#    endif
     // if /dev/tty exists, we can only open it if we have a controlling TTY
-    int devtty = qt_safe_open("/dev/tty", O_RDONLY);
+    int devtty = qt_safe_open(_PATH_TTY, O_RDONLY);
     if (devtty == -1 && (errno == ENOENT || errno == EPERM || errno == ENXIO)) {
         // no /dev/tty, fall back to isatty on stderr
         return isatty(STDERR_FILENO);

src/corelib/io/qfilesystemengine_unix.cpp

@@ -55,6 +55,13 @@
 #include <stdio.h>
 #include <errno.h>
 
+#if QT_HAS_INCLUDE(<paths.h>)
+# include <paths.h>
+#endif
+#ifndef _PATH_TMP           // from <paths.h>
+# define _PATH_TMP          "/tmp"
+#endif
+
 #if defined(Q_OS_MAC)
 # include <QtCore/private/qcore_mac_p.h>
 # include <CoreFoundation/CFBundle.h>
@@ -1507,14 +1514,13 @@ QString QFileSystemEngine::tempPath()
 #else
     QString temp = QFile::decodeName(qgetenv("TMPDIR"));
     if (temp.isEmpty()) {
+        if (false) {
 #if defined(Q_OS_DARWIN) && !defined(QT_BOOTSTRAPPED)
-        if (NSString *nsPath = NSTemporaryDirectory()) {
+        } else if (NSString *nsPath = NSTemporaryDirectory()) {
             temp = QString::fromCFString((CFStringRef)nsPath);
-        } else {
-#else
-        {
 #endif
-            temp = QLatin1String("/tmp");
+        } else {
+            temp = QLatin1String(_PATH_TMP);
         }
     }
     return QDir::cleanPath(temp);

src/corelib/io/qprocess.cpp

@@ -99,6 +99,10 @@ QT_END_NAMESPACE
 #include <private/qcore_unix_p.h>
 #endif
 
+#if QT_HAS_INCLUDE(<paths.h>)
+#include <paths.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 /*!
@@ -2638,6 +2642,8 @@ QString QProcess::nullDevice()
 {
 #ifdef Q_OS_WIN
     return QStringLiteral("\\\\.\\NUL");
+#elif defined(_PATH_DEVNULL)
+    return QStringLiteral(_PATH_DEVNULL);
 #else
     return QStringLiteral("/dev/null");
 #endif

src/corelib/io/qstorageinfo_unix.cpp

@@ -107,6 +107,13 @@
 #  endif // QT_LARGEFILE_SUPPORT
 #endif // Q_OS_BSD4
 
+#if QT_HAS_INCLUDE(<paths.h>)
+#  include <paths.h>
+#endif
+#ifndef _PATH_MOUNTED
+#  define _PATH_MOUNTED     "/etc/mnttab"
+#endif
+
 QT_BEGIN_NAMESPACE
 
 class QStorageIterator
@@ -241,11 +248,9 @@ inline QByteArray QStorageIterator::options() const
 
 #elif defined(Q_OS_SOLARIS)
 
-static const char pathMounted[] = "/etc/mnttab";
-
 inline QStorageIterator::QStorageIterator()
 {
-    const int fd = qt_safe_open(pathMounted, O_RDONLY);
+    const int fd = qt_safe_open(_PATH_MOUNTED, O_RDONLY);
     fp = ::fdopen(fd, "r");
 }
 
@@ -282,11 +287,9 @@ inline QByteArray QStorageIterator::device() const
 
 #elif defined(Q_OS_ANDROID)
 
-static const QLatin1String pathMounted("/proc/mounts");
-
 inline QStorageIterator::QStorageIterator()
 {
-    file.setFileName(pathMounted);
+    file.setFileName(_PATH_MOUNTED);
     file.open(QIODevice::ReadOnly | QIODevice::Text);
 }
 
@@ -339,14 +342,13 @@ inline QByteArray QStorageIterator::options() const
 
 #elif defined(Q_OS_LINUX) || defined(Q_OS_HURD)
 
-static const char pathMounted[] = "/etc/mtab";
 static const int bufferSize = 1024; // 2 paths (mount point+device) and metainfo;
                                     // should be enough
 
 inline QStorageIterator::QStorageIterator() :
     buffer(QByteArray(bufferSize, 0))
 {
-    fp = ::setmntent(pathMounted, "r");
+    fp = ::setmntent(_PATH_MOUNTED, "r");
 }
 
 inline QStorageIterator::~QStorageIterator()