diff --git a/modules/juce_core/files/juce_File.cpp b/modules/juce_core/files/juce_File.cpp
index 2202344a9c..598717e5aa 100644
--- a/modules/juce_core/files/juce_File.cpp
+++ b/modules/juce_core/files/juce_File.cpp
@@ -1009,6 +1009,19 @@ public:
             expect (mb[0] == '0');
         }
 
+        {
+            expect (tempFile.getSize() == 10);
+            FileOutputStream fo (tempFile);
+            expect (fo.openedOk());
+
+            expect (fo.setPosition  (7));
+            expect (fo.truncate().wasOk());
+            expect (tempFile.getSize() == 7);
+            fo.write ("789", 3);
+            fo.flush();
+            expect (tempFile.getSize() == 10);
+        }
+
         beginTest ("Memory-mapped files");
 
         {
diff --git a/modules/juce_core/files/juce_FileOutputStream.h b/modules/juce_core/files/juce_FileOutputStream.h
index 870c3b14b4..6d078c11dc 100644
--- a/modules/juce_core/files/juce_FileOutputStream.h
+++ b/modules/juce_core/files/juce_FileOutputStream.h
@@ -80,6 +80,12 @@ public:
     */
     bool openedOk() const noexcept                      { return status.wasOk(); }
 
+    /** Attempts to truncate the file to the current write position.
+        To truncate a file to a specific size, first use setPosition() to seek to the
+        appropriate location, and then call this method.
+    */
+    Result truncate();
+
     //==============================================================================
     void flush();
     int64 getPosition();
diff --git a/modules/juce_core/native/juce_posix_SharedCode.h b/modules/juce_core/native/juce_posix_SharedCode.h
index 4fd41ec9d5..51f58b14e0 100644
--- a/modules/juce_core/native/juce_posix_SharedCode.h
+++ b/modules/juce_core/native/juce_posix_SharedCode.h
@@ -280,6 +280,11 @@ namespace
     {
         return value == -1 ? getResultForErrno() : Result::ok();
     }
+
+    int getFD (void* handle) noexcept
+    {
+        return (int) (pointer_sized_int) handle;
+    }
 }
 
 bool File::isDirectory() const
@@ -399,10 +404,10 @@ Result File::createDirectoryInternal (const String& fileName) const
     return getResultForReturnValue (mkdir (fileName.toUTF8(), 0777));
 }
 
-//==============================================================================
+//=====================================================================
 int64 juce_fileSetPosition (void* handle, int64 pos)
 {
-    if (handle != 0 && lseek ((int) (pointer_sized_int) handle, pos, SEEK_SET) == pos)
+    if (handle != 0 && lseek (getFD (handle), pos, SEEK_SET) == pos)
         return pos;
 
     return -1;
@@ -424,7 +429,7 @@ void FileInputStream::closeHandle()
 {
     if (fileHandle != 0)
     {
-        close ((int) (pointer_sized_int) fileHandle);
+        close (getFD (fileHandle));
         fileHandle = 0;
     }
 }
@@ -435,7 +440,7 @@ size_t FileInputStream::readInternal (void* const buffer, const size_t numBytes)
 
     if (fileHandle != 0)
     {
-        result = ::read ((int) (pointer_sized_int) fileHandle, buffer, numBytes);
+        result = ::read (getFD (fileHandle), buffer, numBytes);
 
         if (result < 0)
         {
@@ -488,7 +493,7 @@ void FileOutputStream::closeHandle()
 {
     if (fileHandle != 0)
     {
-        close ((int) (pointer_sized_int) fileHandle);
+        close (getFD (fileHandle));
         fileHandle = 0;
     }
 }
@@ -499,7 +504,7 @@ int FileOutputStream::writeInternal (const void* const data, const int numBytes)
 
     if (fileHandle != 0)
     {
-        result = ::write ((int) (pointer_sized_int) fileHandle, data, numBytes);
+        result = ::write (getFD (fileHandle), data, numBytes);
 
         if (result == -1)
             status = getResultForErrno();
@@ -511,10 +516,19 @@ int FileOutputStream::writeInternal (const void* const data, const int numBytes)
 void FileOutputStream::flushInternal()
 {
     if (fileHandle != 0)
-        if (fsync ((int) (pointer_sized_int) fileHandle) == -1)
+        if (fsync (getFD (fileHandle)) == -1)
             status = getResultForErrno();
 }
 
+Result FileOutputStream::truncate()
+{
+    if (fileHandle == 0)
+        return status;
+
+    flush();
+    return getResultForReturnValue (ftruncate (getFD (fileHandle), (off_t) currentPosition));
+}
+
 //==============================================================================
 MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMode mode)
     : address (nullptr),
diff --git a/modules/juce_core/native/juce_win32_Files.cpp b/modules/juce_core/native/juce_win32_Files.cpp
index f9b30bab98..8dabf7db03 100644
--- a/modules/juce_core/native/juce_win32_Files.cpp
+++ b/modules/juce_core/native/juce_win32_Files.cpp
@@ -289,6 +289,16 @@ void FileOutputStream::flushInternal()
             status = WindowsFileHelpers::getResultForLastError();
 }
 
+Result FileOutputStream::truncate()
+{
+    if (fileHandle == nullptr)
+        return status;
+
+    flush();
+    return SetEndOfFile ((HANDLE) fileHandle) ? Result::ok()
+                                              : WindowsFileHelpers::getResultForLastError();
+}
+
 //==============================================================================
 MemoryMappedFile::MemoryMappedFile (const File& file, MemoryMappedFile::AccessMode mode)
     : address (nullptr),
diff --git a/modules/juce_gui_basics/layout/juce_Viewport.cpp b/modules/juce_gui_basics/layout/juce_Viewport.cpp
index 7edd16eb4b..22c2d6ef91 100644
--- a/modules/juce_gui_basics/layout/juce_Viewport.cpp
+++ b/modules/juce_gui_basics/layout/juce_Viewport.cpp
@@ -185,7 +185,7 @@ void Viewport::updateVisibleArea()
     const bool canShowHBar = showHScrollbar && canShowAnyBars;
     const bool canShowVBar = showVScrollbar && canShowAnyBars;
 
-    bool hBarVisible, vBarVisible;
+    bool hBarVisible = false, vBarVisible = false;
     Rectangle<int> contentArea;
 
     for (int i = 3; --i >= 0;)