diff --git a/modules/juce_core/files/juce_DirectoryIterator.cpp b/modules/juce_core/files/juce_DirectoryIterator.cpp
index 5a8a952bca..7bed2d790a 100644
--- a/modules/juce_core/files/juce_DirectoryIterator.cpp
+++ b/modules/juce_core/files/juce_DirectoryIterator.cpp
@@ -24,16 +24,13 @@ namespace juce
 {
 
 DirectoryIterator::DirectoryIterator (const File& directory, bool recursive,
-                                      const String& pattern, const int type)
+                                      const String& pattern, int type)
   : wildCards (parseWildcards (pattern)),
     fileFinder (directory, (recursive || wildCards.size() > 1) ? "*" : pattern),
     wildCard (pattern),
     path (File::addTrailingSeparator (directory.getFullPathName())),
-    index (-1),
-    totalNumFiles (-1),
     whatToLookFor (type),
-    isRecursive (recursive),
-    hasBeenAdvanced (false)
+    isRecursive (recursive)
 {
     // you have to specify the type of files you're looking for!
     jassert ((type & (File::findFiles | File::findDirectories)) != 0);
@@ -53,10 +50,10 @@ StringArray DirectoryIterator::parseWildcards (const String& pattern)
     return s;
 }
 
-bool DirectoryIterator::fileMatches (const StringArray& wildCards, const String& filename)
+bool DirectoryIterator::fileMatches (const StringArray& wildcards, const String& filename)
 {
-    for (int i = 0; i < wildCards.size(); ++i)
-        if (filename.matchesWildcard (wildCards[i], ! File::areFileNamesCaseSensitive()))
+    for (auto& w : wildcards)
+        if (filename.matchesWildcard (w, ! File::areFileNamesCaseSensitive()))
             return true;
 
     return false;
@@ -67,8 +64,8 @@ bool DirectoryIterator::next()
     return next (nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
 }
 
-bool DirectoryIterator::next (bool* const isDirResult, bool* const isHiddenResult, int64* const fileSize,
-                              Time* const modTime, Time* const creationTime, bool* const isReadOnly)
+bool DirectoryIterator::next (bool* isDirResult, bool* isHiddenResult, int64* fileSize,
+                              Time* modTime, Time* creationTime, bool* isReadOnly)
 {
     for (;;)
     {
@@ -156,8 +153,8 @@ float DirectoryIterator::getEstimatedProgress() const
     if (totalNumFiles <= 0)
         return 0.0f;
 
-    const float detailedIndex = (subIterator != nullptr) ? index + subIterator->getEstimatedProgress()
-                                                         : (float) index;
+    auto detailedIndex = (subIterator != nullptr) ? index + subIterator->getEstimatedProgress()
+                                                  : (float) index;
 
     return jlimit (0.0f, 1.0f, detailedIndex / totalNumFiles);
 }
diff --git a/modules/juce_core/files/juce_DirectoryIterator.h b/modules/juce_core/files/juce_DirectoryIterator.h
index 667cd8b49f..44cf38fbfc 100644
--- a/modules/juce_core/files/juce_DirectoryIterator.h
+++ b/modules/juce_core/files/juce_DirectoryIterator.h
@@ -140,11 +140,11 @@ private:
     StringArray wildCards;
     NativeIterator fileFinder;
     String wildCard, path;
-    int index;
-    mutable int totalNumFiles;
+    int index = -1;
+    mutable int totalNumFiles = -1;
     const int whatToLookFor;
     const bool isRecursive;
-    bool hasBeenAdvanced;
+    bool hasBeenAdvanced = false;
     ScopedPointer<DirectoryIterator> subIterator;
     File currentFile;
 
diff --git a/modules/juce_core/files/juce_FileInputStream.cpp b/modules/juce_core/files/juce_FileInputStream.cpp
index 638abf9831..0b6ab6361b 100644
--- a/modules/juce_core/files/juce_FileInputStream.cpp
+++ b/modules/juce_core/files/juce_FileInputStream.cpp
@@ -27,11 +27,7 @@ int64 juce_fileSetPosition (void* handle, int64 pos);
 
 
 //==============================================================================
-FileInputStream::FileInputStream (const File& f)
-    : file (f),
-      fileHandle (nullptr),
-      currentPosition (0),
-      status (Result::ok())
+FileInputStream::FileInputStream (const File& f)  : file (f)
 {
     openHandle();
 }
@@ -53,7 +49,7 @@ int FileInputStream::read (void* buffer, int bytesToRead)
     // sign that something is broken!
     jassert (buffer != nullptr && bytesToRead >= 0);
 
-    const size_t num = readInternal (buffer, (size_t) bytesToRead);
+    auto num = readInternal (buffer, (size_t) bytesToRead);
     currentPosition += (int64) num;
 
     return (int) num;
diff --git a/modules/juce_core/files/juce_FileInputStream.h b/modules/juce_core/files/juce_FileInputStream.h
index 9fd84b0251..bf83dd6628 100644
--- a/modules/juce_core/files/juce_FileInputStream.h
+++ b/modules/juce_core/files/juce_FileInputStream.h
@@ -75,9 +75,9 @@ public:
 private:
     //==============================================================================
     const File file;
-    void* fileHandle;
-    int64 currentPosition;
-    Result status;
+    void* fileHandle = nullptr;
+    int64 currentPosition = 0;
+    Result status { Result::ok() };
 
     void openHandle();
     size_t readInternal (void*, size_t);
diff --git a/modules/juce_core/files/juce_FileOutputStream.cpp b/modules/juce_core/files/juce_FileOutputStream.cpp
index 495104380d..4d8e7b4576 100644
--- a/modules/juce_core/files/juce_FileOutputStream.cpp
+++ b/modules/juce_core/files/juce_FileOutputStream.cpp
@@ -28,11 +28,7 @@ int64 juce_fileSetPosition (void* handle, int64 pos);
 //==============================================================================
 FileOutputStream::FileOutputStream (const File& f, const size_t bufferSizeToUse)
     : file (f),
-      fileHandle (nullptr),
-      status (Result::ok()),
-      currentPosition (0),
       bufferSize (bufferSizeToUse),
-      bytesInBuffer (0),
       buffer (jmax (bufferSizeToUse, (size_t) 16))
 {
     openHandle();
@@ -102,7 +98,7 @@ bool FileOutputStream::write (const void* const src, const size_t numBytes)
         }
         else
         {
-            const ssize_t bytesWritten = writeInternal (src, numBytes);
+            auto bytesWritten = writeInternal (src, numBytes);
 
             if (bytesWritten < 0)
                 return false;
diff --git a/modules/juce_core/files/juce_FileOutputStream.h b/modules/juce_core/files/juce_FileOutputStream.h
index 3e1100ce76..ebe50fe64f 100644
--- a/modules/juce_core/files/juce_FileOutputStream.h
+++ b/modules/juce_core/files/juce_FileOutputStream.h
@@ -94,10 +94,10 @@ public:
 private:
     //==============================================================================
     File file;
-    void* fileHandle;
-    Result status;
-    int64 currentPosition;
-    size_t bufferSize, bytesInBuffer;
+    void* fileHandle = nullptr;
+    Result status { Result::ok() };
+    int64 currentPosition = 0;
+    size_t bufferSize, bytesInBuffer = 0;
     HeapBlock<char> buffer;
 
     void openHandle();
diff --git a/modules/juce_core/files/juce_FileSearchPath.cpp b/modules/juce_core/files/juce_FileSearchPath.cpp
index baa2539f6f..4299ec6fb7 100644
--- a/modules/juce_core/files/juce_FileSearchPath.cpp
+++ b/modules/juce_core/files/juce_FileSearchPath.cpp
@@ -55,8 +55,8 @@ void FileSearchPath::init (const String& path)
     directories.trim();
     directories.removeEmptyStrings();
 
-    for (int i = directories.size(); --i >= 0;)
-        directories.set (i, directories[i].unquoted());
+    for (auto& d : directories)
+        d = d.unquoted();
 }
 
 int FileSearchPath::getNumPaths() const
@@ -64,37 +64,38 @@ int FileSearchPath::getNumPaths() const
     return directories.size();
 }
 
-File FileSearchPath::operator[] (const int index) const
+File FileSearchPath::operator[] (int index) const
 {
-    return File (directories [index]);
+    return File (directories[index]);
 }
 
 String FileSearchPath::toString() const
 {
-    StringArray directories2 (directories);
-    for (int i = directories2.size(); --i >= 0;)
-        if (directories2[i].containsChar (';'))
-            directories2.set (i, directories2[i].quoted());
+    auto dirs = directories;
 
-    return directories2.joinIntoString (";");
+    for (auto& d : dirs)
+        if (d.containsChar (';'))
+            d = d.quoted();
+
+    return dirs.joinIntoString (";");
 }
 
-void FileSearchPath::add (const File& dir, const int insertIndex)
+void FileSearchPath::add (const File& dir, int insertIndex)
 {
     directories.insert (insertIndex, dir.getFullPathName());
 }
 
 bool FileSearchPath::addIfNotAlreadyThere (const File& dir)
 {
-    for (int i = 0; i < directories.size(); ++i)
-        if (File (directories[i]) == dir)
+    for (auto& d : directories)
+        if (File (d) == dir)
             return false;
 
     add (dir);
     return true;
 }
 
-void FileSearchPath::remove (const int index)
+void FileSearchPath::remove (int index)
 {
     directories.remove (index);
 }
@@ -115,7 +116,7 @@ void FileSearchPath::removeRedundantPaths()
         {
             const File d2 (directories[j]);
 
-            if ((i != j) && (d1.isAChildOf (d2) || d1 == d2))
+            if (i != j && (d1.isAChildOf (d2) || d1 == d2))
             {
                 directories.remove (i);
                 break;
@@ -131,18 +132,13 @@ void FileSearchPath::removeNonExistentPaths()
             directories.remove (i);
 }
 
-int FileSearchPath::findChildFiles (Array<File>& results,
-                                    const int whatToLookFor,
-                                    const bool searchRecursively,
-                                    const String& wildCardPattern) const
+int FileSearchPath::findChildFiles (Array<File>& results, int whatToLookFor,
+                                    bool recurse, const String& wildcard) const
 {
     int total = 0;
 
-    for (int i = 0; i < directories.size(); ++i)
-        total += operator[] (i).findChildFiles (results,
-                                                whatToLookFor,
-                                                searchRecursively,
-                                                wildCardPattern);
+    for (auto& d : directories)
+        total += File (d).findChildFiles (results, whatToLookFor, recurse, wildcard);
 
     return total;
 }
@@ -150,18 +146,16 @@ int FileSearchPath::findChildFiles (Array<File>& results,
 bool FileSearchPath::isFileInPath (const File& fileToCheck,
                                    const bool checkRecursively) const
 {
-    for (int i = directories.size(); --i >= 0;)
+    for (auto& d : directories)
     {
-        const File d (directories[i]);
-
         if (checkRecursively)
         {
-            if (fileToCheck.isAChildOf (d))
+            if (fileToCheck.isAChildOf (File (d)))
                 return true;
         }
         else
         {
-            if (fileToCheck.getParentDirectory() == d)
+            if (fileToCheck.getParentDirectory() == File (d))
                 return true;
         }
     }
diff --git a/modules/juce_core/files/juce_TemporaryFile.cpp b/modules/juce_core/files/juce_TemporaryFile.cpp
index 7010677920..794d6a1a2b 100644
--- a/modules/juce_core/files/juce_TemporaryFile.cpp
+++ b/modules/juce_core/files/juce_TemporaryFile.cpp
@@ -24,7 +24,7 @@ namespace juce
 {
 
 static File createTempFile (const File& parentDirectory, String name,
-                            const String& suffix, const int optionFlags)
+                            const String& suffix, int optionFlags)
 {
     if ((optionFlags & TemporaryFile::useHiddenFile) != 0)
         name = "." + name;
diff --git a/modules/juce_core/files/juce_WildcardFileFilter.cpp b/modules/juce_core/files/juce_WildcardFileFilter.cpp
index 8db43f34e7..03e3085d52 100644
--- a/modules/juce_core/files/juce_WildcardFileFilter.cpp
+++ b/modules/juce_core/files/juce_WildcardFileFilter.cpp
@@ -26,23 +26,22 @@ namespace juce
 static void parseWildcard (const String& pattern, StringArray& result)
 {
     result.addTokens (pattern.toLowerCase(), ";,", "\"'");
-
     result.trim();
     result.removeEmptyStrings();
 
     // special case for *.*, because people use it to mean "any file", but it
     // would actually ignore files with no extension.
-    for (int i = result.size(); --i >= 0;)
-        if (result[i] == "*.*")
-            result.set (i, "*");
+    for (auto& r : result)
+        if (r == "*.*")
+            r = "*";
 }
 
 static bool matchWildcard (const File& file, const StringArray& wildcards)
 {
-    const String filename (file.getFileName());
+    auto filename = file.getFileName();
 
-    for (int i = wildcards.size(); --i >= 0;)
-        if (filename.matchesWildcard (wildcards[i], true))
+    for (auto& w : wildcards)
+        if (filename.matchesWildcard (w, true))
             return true;
 
     return false;
diff --git a/modules/juce_core/streams/juce_BufferedInputStream.cpp b/modules/juce_core/streams/juce_BufferedInputStream.cpp
index d53484fe22..b94ed0e068 100644
--- a/modules/juce_core/streams/juce_BufferedInputStream.cpp
+++ b/modules/juce_core/streams/juce_BufferedInputStream.cpp
@@ -59,8 +59,10 @@ BufferedInputStream::~BufferedInputStream()
 //==============================================================================
 char BufferedInputStream::peekByte()
 {
-    ensureBuffered();
-    return position < lastReadPos ? *(buffer + (int) (position - bufferStart)) : 0;
+    if (! ensureBuffered())
+        return 0;
+
+    return position < lastReadPos ? buffer[(int) (position - bufferStart)] : 0;
 }
 
 int64 BufferedInputStream::getTotalLength()
@@ -84,7 +86,7 @@ bool BufferedInputStream::isExhausted()
     return position >= lastReadPos && source->isExhausted();
 }
 
-void BufferedInputStream::ensureBuffered()
+bool BufferedInputStream::ensureBuffered()
 {
     auto bufferEndOverlap = lastReadPos - bufferOverlap;
 
@@ -100,24 +102,35 @@ void BufferedInputStream::ensureBuffered()
             memmove (buffer, buffer + (int) (position - bufferStart), (size_t) bytesToKeep);
 
             bufferStart = position;
-
             bytesRead = source->read (buffer + bytesToKeep,
                                       (int) (bufferSize - bytesToKeep));
 
+            if (bytesRead < 0)
+                return false;
+
             lastReadPos += bytesRead;
             bytesRead += bytesToKeep;
         }
         else
         {
             bufferStart = position;
-            source->setPosition (bufferStart);
+
+            if (! source->setPosition (bufferStart))
+                return false;
+
             bytesRead = source->read (buffer, bufferSize);
+
+            if (bytesRead < 0)
+                return false;
+
             lastReadPos = bufferStart + bytesRead;
         }
 
         while (bytesRead < bufferSize)
-            buffer [bytesRead++] = 0;
+            buffer[bytesRead++] = 0;
     }
+
+    return true;
 }
 
 int BufferedInputStream::read (void* destBuffer, int maxBytesToRead)
@@ -133,7 +146,8 @@ int BufferedInputStream::read (void* destBuffer, int maxBytesToRead)
     }
 
     if (position < bufferStart || position >= lastReadPos)
-        ensureBuffered();
+        if (! ensureBuffered())
+            return 0;
 
     int bytesRead = 0;
 
@@ -151,12 +165,10 @@ int BufferedInputStream::read (void* destBuffer, int maxBytesToRead)
         }
 
         auto oldLastReadPos = lastReadPos;
-        ensureBuffered();
 
-        if (oldLastReadPos == lastReadPos)
-            break; // if ensureBuffered() failed to read any more data, bail out
-
-        if (isExhausted())
+        if (! ensureBuffered()
+             || oldLastReadPos == lastReadPos
+             || isExhausted())
             break;
     }
 
diff --git a/modules/juce_core/streams/juce_BufferedInputStream.h b/modules/juce_core/streams/juce_BufferedInputStream.h
index 8719b66c5b..8a5da9ab2d 100644
--- a/modules/juce_core/streams/juce_BufferedInputStream.h
+++ b/modules/juce_core/streams/juce_BufferedInputStream.h
@@ -80,7 +80,7 @@ private:
     int bufferSize;
     int64 position, lastReadPos = 0, bufferStart, bufferOverlap = 128;
     HeapBlock<char> buffer;
-    void ensureBuffered();
+    bool ensureBuffered();
 
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (BufferedInputStream)
 };
diff --git a/modules/juce_core/streams/juce_MemoryInputStream.cpp b/modules/juce_core/streams/juce_MemoryInputStream.cpp
index 041b24ec8c..3739af3374 100644
--- a/modules/juce_core/streams/juce_MemoryInputStream.cpp
+++ b/modules/juce_core/streams/juce_MemoryInputStream.cpp
@@ -23,24 +23,19 @@
 namespace juce
 {
 
-MemoryInputStream::MemoryInputStream (const void* const sourceData,
-                                      const size_t sourceDataSize,
-                                      const bool keepInternalCopy)
+MemoryInputStream::MemoryInputStream (const void* sourceData, size_t sourceDataSize, bool keepCopy)
     : data (sourceData),
-      dataSize (sourceDataSize),
-      position (0)
+      dataSize (sourceDataSize)
 {
-    if (keepInternalCopy)
+    if (keepCopy)
         createInternalCopy();
 }
 
-MemoryInputStream::MemoryInputStream (const MemoryBlock& sourceData,
-                                      const bool keepInternalCopy)
+MemoryInputStream::MemoryInputStream (const MemoryBlock& sourceData, bool keepCopy)
     : data (sourceData.getData()),
-      dataSize (sourceData.getSize()),
-      position (0)
+      dataSize (sourceData.getSize())
 {
-    if (keepInternalCopy)
+    if (keepCopy)
         createInternalCopy();
 }
 
@@ -60,14 +55,14 @@ int64 MemoryInputStream::getTotalLength()
     return (int64) dataSize;
 }
 
-int MemoryInputStream::read (void* const buffer, const int howMany)
+int MemoryInputStream::read (void* buffer, int howMany)
 {
     jassert (buffer != nullptr && howMany >= 0);
 
     if (howMany <= 0 || position >= dataSize)
         return 0;
 
-    const size_t num = jmin ((size_t) howMany, dataSize - position);
+    auto num = jmin ((size_t) howMany, dataSize - position);
 
     if (num > 0)
     {
diff --git a/modules/juce_core/streams/juce_MemoryInputStream.h b/modules/juce_core/streams/juce_MemoryInputStream.h
index 86373ca657..8b84816660 100644
--- a/modules/juce_core/streams/juce_MemoryInputStream.h
+++ b/modules/juce_core/streams/juce_MemoryInputStream.h
@@ -71,7 +71,7 @@ public:
 
     //==============================================================================
     int64 getPosition() override;
-    bool setPosition (int64 pos) override;
+    bool setPosition (int64) override;
     int64 getTotalLength() override;
     bool isExhausted() override;
     int read (void* destBuffer, int maxBytesToRead) override;
@@ -79,7 +79,7 @@ public:
 private:
     //==============================================================================
     const void* data;
-    size_t dataSize, position;
+    size_t dataSize, position = 0;
     HeapBlock<char> internalCopy;
 
     void createInternalCopy();
diff --git a/modules/juce_core/streams/juce_SubregionStream.cpp b/modules/juce_core/streams/juce_SubregionStream.cpp
index c7b67900cb..96856a76e0 100644
--- a/modules/juce_core/streams/juce_SubregionStream.cpp
+++ b/modules/juce_core/streams/juce_SubregionStream.cpp
@@ -23,9 +23,9 @@
 namespace juce
 {
 
-SubregionStream::SubregionStream (InputStream* const sourceStream,
-                                  const int64 start, const int64 length,
-                                  const bool deleteSourceWhenDestroyed)
+SubregionStream::SubregionStream (InputStream* sourceStream,
+                                  int64 start, int64 length,
+                                  bool deleteSourceWhenDestroyed)
   : source (sourceStream, deleteSourceWhenDestroyed),
     startPositionInSourceStream (start),
     lengthOfSourceStream (length)
@@ -39,7 +39,7 @@ SubregionStream::~SubregionStream()
 
 int64 SubregionStream::getTotalLength()
 {
-    const int64 srcLen = source->getTotalLength() - startPositionInSourceStream;
+    auto srcLen = source->getTotalLength() - startPositionInSourceStream;
 
     return lengthOfSourceStream >= 0 ? jmin (lengthOfSourceStream, srcLen)
                                      : srcLen;
diff --git a/modules/juce_core/zip/juce_GZIPDecompressorInputStream.cpp b/modules/juce_core/zip/juce_GZIPDecompressorInputStream.cpp
index 0bae4d39d6..72a18ff20f 100644
--- a/modules/juce_core/zip/juce_GZIPDecompressorInputStream.cpp
+++ b/modules/juce_core/zip/juce_GZIPDecompressorInputStream.cpp
@@ -191,10 +191,7 @@ GZIPDecompressorInputStream::GZIPDecompressorInputStream (InputStream* source, b
   : sourceStream (source, deleteSourceWhenDestroyed),
     uncompressedStreamLength (uncompressedLength),
     format (f),
-    isEof (false),
-    activeBufferSize (0),
     originalSourcePos (source->getPosition()),
-    currentPos (0),
     buffer ((size_t) GZIPDecompressHelper::gzipDecompBufferSize),
     helper (new GZIPDecompressHelper (f))
 {
@@ -204,10 +201,7 @@ GZIPDecompressorInputStream::GZIPDecompressorInputStream (InputStream& source)
   : sourceStream (&source, false),
     uncompressedStreamLength (-1),
     format (zlibFormat),
-    isEof (false),
-    activeBufferSize (0),
     originalSourcePos (source.getPosition()),
-    currentPos (0),
     buffer ((size_t) GZIPDecompressHelper::gzipDecompBufferSize),
     helper (new GZIPDecompressHelper (zlibFormat))
 {
@@ -229,11 +223,11 @@ int GZIPDecompressorInputStream::read (void* destBuffer, int howMany)
     if (howMany > 0 && ! isEof)
     {
         int numRead = 0;
-        uint8* d = static_cast<uint8*> (destBuffer);
+        auto d = static_cast<uint8*> (destBuffer);
 
         while (! helper->error)
         {
-            const int n = helper->doNextBlock (d, (unsigned int) howMany);
+            auto n = helper->doNextBlock (d, (unsigned int) howMany);
             currentPos += n;
 
             if (n == 0)
diff --git a/modules/juce_core/zip/juce_GZIPDecompressorInputStream.h b/modules/juce_core/zip/juce_GZIPDecompressorInputStream.h
index a7edadc04d..171ccd8ef9 100644
--- a/modules/juce_core/zip/juce_GZIPDecompressorInputStream.h
+++ b/modules/juce_core/zip/juce_GZIPDecompressorInputStream.h
@@ -82,9 +82,9 @@ private:
     OptionalScopedPointer<InputStream> sourceStream;
     const int64 uncompressedStreamLength;
     const Format format;
-    bool isEof;
-    int activeBufferSize;
-    int64 originalSourcePos, currentPos;
+    bool isEof = false;
+    int activeBufferSize = 0;
+    int64 originalSourcePos, currentPos = 0;
     HeapBlock<uint8> buffer;
 
     class GZIPDecompressHelper;