diff --git a/build/jam/BuildSetup b/build/jam/BuildSetup
index a9c2dc432a..c91efe4d08 100644
--- a/build/jam/BuildSetup
+++ b/build/jam/BuildSetup
@@ -1033,15 +1033,12 @@ if $(HAIKU_GCC_VERSION[1]) = 2 {
 			: $(scope) ;
 	}
 } else {
-# TODO: Enable after updating to a newer gcc 4 version that supports -Wno-error!
 	# -Wuninitialized gives too many false positives.
-#	rule EnableWerror dirTokens : scope {
-#		AppendToConfigVar CCFLAGS : HAIKU_TOP $(dirTokens)
-#			: -Werror -Wno-error=uninitialized : $(scope) ;
-#		AppendToConfigVar C++FLAGS : HAIKU_TOP $(dirTokens)
-#			: -Werror -Wno-error=uninitialized : $(scope) ;
-#	}
 	rule EnableWerror dirTokens : scope {
+		AppendToConfigVar CCFLAGS : HAIKU_TOP $(dirTokens)
+			: -Werror -Wno-error=uninitialized : $(scope) ;
+		AppendToConfigVar C++FLAGS : HAIKU_TOP $(dirTokens)
+			: -Werror -Wno-error=uninitialized : $(scope) ;
 	}
 }
 
diff --git a/headers/os/app/PropertyInfo.h b/headers/os/app/PropertyInfo.h
index 780903c511..5990dde892 100644
--- a/headers/os/app/PropertyInfo.h
+++ b/headers/os/app/PropertyInfo.h
@@ -42,7 +42,7 @@ struct _oproperty_info_;
 struct compound_type {
 	struct field_pair {
 #if __GNUC__ > 2
-	const
+		const
 #endif
 		char		*name;			// name of entry in message
 		type_code	type;			// type_code of entry in message
diff --git a/headers/private/storage/sniffer/Parser.h b/headers/private/storage/sniffer/Parser.h
index 2e2e7d86a4..0d5629aa09 100644
--- a/headers/private/storage/sniffer/Parser.h
+++ b/headers/private/storage/sniffer/Parser.h
@@ -54,7 +54,7 @@ typedef enum TokenType {
 	CharacterString,
 	Integer,
 	FloatingPoint
-};
+} TokenType;
 
 /*! \brief Returns a NULL-terminated string contating the
 		   name of the given token type
diff --git a/src/kits/app/Application.cpp b/src/kits/app/Application.cpp
index 51b944941e..3ef471b054 100644
--- a/src/kits/app/Application.cpp
+++ b/src/kits/app/Application.cpp
@@ -1498,7 +1498,7 @@ BApplication::_WindowAt(uint32 index, bool includeMenus) const
 	uint32 count = gLooperList.CountLoopers();
 	for (uint32 i = 0; i < count && index < count; i++) {
 		BWindow* window = dynamic_cast<BWindow*>(gLooperList.LooperAt(i));
-		if (window == NULL || window != NULL && window->fOffscreen 
+		if (window == NULL || (window != NULL && window->fOffscreen)
 			|| (!includeMenus && dynamic_cast<BMenuWindow *>(window) != NULL)) {
 			index++;
 			continue;
diff --git a/src/kits/app/Messenger.cpp b/src/kits/app/Messenger.cpp
index 828df46353..3c005642e7 100644
--- a/src/kits/app/Messenger.cpp
+++ b/src/kits/app/Messenger.cpp
@@ -572,11 +572,11 @@ operator<(const BMessenger &_a, const BMessenger &_b)
 	// 3. fPreferredTarget
 	// fTeam is insignificant
 	return (a.Port() < b.Port()
-			|| a.Port() == b.Port()
+			|| (a.Port() == b.Port()
 				&& (a.Token() < b.Token()
-					|| a.Token() == b.Token()
+					|| (a.Token() == b.Token()
 						&& !a.IsPreferredTarget()
-						&& b.IsPreferredTarget()));
+						&& b.IsPreferredTarget()))));
 }
 
 
diff --git a/src/kits/app/PropertyInfo.cpp b/src/kits/app/PropertyInfo.cpp
index afb5e0791c..10f45b3e09 100644
--- a/src/kits/app/PropertyInfo.cpp
+++ b/src/kits/app/PropertyInfo.cpp
@@ -501,15 +501,15 @@ BPropertyInfo::FreeMem()
 
 	if (fPropInfo != NULL) {
 		for (i = 0; i < fPropCount; i++) {
-			free(fPropInfo[i].name);
-			free(fPropInfo[i].usage);
+			free((char *)fPropInfo[i].name);
+			free((char *)fPropInfo[i].usage);
 
 			for (j = 0; j < 3; j++) {
 				for (k = 0; k < 5; k++) {
 					if (fPropInfo[i].ctypes[j].pairs[k].name == NULL)
 						break;
 
-					free(fPropInfo[i].ctypes[j].pairs[k].name);
+					free((char *)fPropInfo[i].ctypes[j].pairs[k].name);
 				}
 
 				if (fPropInfo[i].ctypes[j].pairs[0].name == NULL)
@@ -523,8 +523,8 @@ BPropertyInfo::FreeMem()
 
 	if (fValueInfo != NULL) {
 		for (i = 0; i < fValueCount; i++) {
-			free(fValueInfo[i].name);
-			free(fValueInfo[i].usage);
+			free((char *)fValueInfo[i].name);
+			free((char *)fValueInfo[i].usage);
 		}
 		free(fValueInfo);
 		fValueInfo = NULL;
diff --git a/src/kits/interface/ColorConversion.cpp b/src/kits/interface/ColorConversion.cpp
index baa6aa9040..d332a1f855 100644
--- a/src/kits/interface/ColorConversion.cpp
+++ b/src/kits/interface/ColorConversion.cpp
@@ -250,7 +250,7 @@ inline
 uint8
 PaletteConverter::IndexForRGB16(uint16 rgb) const
 {
-	return fColorMap->index_map[(rgb >> 1) & 0x7fe0 | rgb & 0x1f];
+	return fColorMap->index_map[((rgb >> 1) & 0x7fe0) | (rgb & 0x1f)];
 }
 
 
@@ -487,7 +487,7 @@ ReadRGB24(const uint8 **source, int32 index)
 void
 WriteGray8(uint8 **dest, uint8 *data, int32 index)
 {
-	**dest = data[2] * 308 + data[1] * 600 + data[0] * 116 >> 10;
+	**dest = (data[2] * 308 + data[1] * 600 + data[0] * 116) >> 10;
 	// this would boost the speed but is less accurate:
 	//*dest = (data[2] << 8) + (data[1] << 9) + (data[0] << 8) >> 10;
 	(*dest)++;
@@ -584,9 +584,9 @@ ConvertBits(const srcByte *srcBits, dstByte *dstBits, int32 srcBitsLength,
 	}
 
 	srcBits = (srcByte*)((uint8*)srcBits + (srcOffsetY * srcBitsPerRow + srcOffsetX
-		* srcBitsPerPixel >> 3));
+		* (srcBitsPerPixel >> 3)));
 	dstBits = (dstByte*)((uint8*)dstBits + (dstOffsetY * dstBitsPerRow + dstOffsetX
-		* dstBitsPerPixel >> 3));
+		* (dstBitsPerPixel >> 3)));
 
 	// Ensure that the width fits
 	int32 srcWidth = (srcBitsPerRow - srcOffsetX * srcBitsPerPixel)
diff --git a/src/kits/interface/ListView.cpp b/src/kits/interface/ListView.cpp
index 3b2e0ad595..0eecf2a9c3 100644
--- a/src/kits/interface/ListView.cpp
+++ b/src/kits/interface/ListView.cpp
@@ -1527,7 +1527,7 @@ BListView::_DeselectAll(int32 exceptFrom, int32 exceptTo)
 bool
 BListView::_TryInitiateDrag(BPoint where)
 {
-	if (!fTrack->try_drag | fTrack->item_index < 0)
+	if (!fTrack->try_drag || fTrack->item_index < 0)
 		return false;
 
 	BPoint offset = where - fTrack->drag_start;
diff --git a/src/kits/interface/Menu.cpp b/src/kits/interface/Menu.cpp
index e2590e9946..6f9808d637 100644
--- a/src/kits/interface/Menu.cpp
+++ b/src/kits/interface/Menu.cpp
@@ -2626,8 +2626,8 @@ BMenu::_OkToProceed(BMenuItem* item)
 	// TODO: I added the check for BMenuBar to solve a problem with Deskbar.
 	// BeOS seems to do something similar. This could also be a bug in Deskbar, though.
 	if ((buttons != 0 && stickyMode)
-		|| (dynamic_cast<BMenuBar *>(this) == NULL
-			&& (buttons == 0 && !stickyMode) || _HitTestItems(where) != item))
+		|| ((dynamic_cast<BMenuBar *>(this) == NULL
+			&& (buttons == 0 && !stickyMode)) || _HitTestItems(where) != item))
 		return false;
 
 	return true;
diff --git a/src/kits/interface/MenuItem.cpp b/src/kits/interface/MenuItem.cpp
index 22a0721cce..b99f952a31 100644
--- a/src/kits/interface/MenuItem.cpp
+++ b/src/kits/interface/MenuItem.cpp
@@ -755,7 +755,7 @@ BMenuItem::_DrawShortcutSymbol()
 		where.x -= fBounds.Height() - 3;
 
 	const float ascent = MenuPrivate(fSuper).Ascent();
-	if (fShortcutChar < B_SPACE && kUTF8ControlMap[fShortcutChar])
+	if (fShortcutChar < B_SPACE && kUTF8ControlMap[(int)fShortcutChar])
 		_DrawControlChar(fShortcutChar, where + BPoint(0, ascent));
 	else
 		fSuper->DrawChar(fShortcutChar, where + BPoint(0, ascent));
@@ -849,8 +849,8 @@ BMenuItem::_DrawControlChar(char shortcut, BPoint where)
 	// TODO: If needed, take another font for the control characters
 	//	(or have font overlays in the app_server!)
 	const char* symbol = " ";
-	if (kUTF8ControlMap[fShortcutChar])
-		symbol = kUTF8ControlMap[fShortcutChar];
+	if (kUTF8ControlMap[(int)fShortcutChar])
+		symbol = kUTF8ControlMap[(int)fShortcutChar];
 
 	fSuper->DrawString(symbol, where);
 }
diff --git a/src/kits/interface/Slider.cpp b/src/kits/interface/Slider.cpp
index 8b48238334..8ea1d652f9 100644
--- a/src/kits/interface/Slider.cpp
+++ b/src/kits/interface/Slider.cpp
@@ -874,10 +874,12 @@ BSlider::DrawBar()
 		barColor.red	= (fBarColor.red + no_tint.red) / 2;
 		barColor.green	= (fBarColor.green + no_tint.green) / 2;
 		barColor.blue	= (fBarColor.blue + no_tint.blue) / 2;
+		barColor.alpha	= 255;
 
 		fillColor.red	= (fFillColor.red + no_tint.red) / 2;
 		fillColor.green	= (fFillColor.green + no_tint.green) / 2;
 		fillColor.blue	= (fFillColor.blue + no_tint.blue) / 2;
+		fillColor.alpha	= 255;
 	}
 
 	// exclude the block thumb from the bar filling
@@ -1172,8 +1174,8 @@ BSlider::UpdateTextChanged()
 
 	const char* oldUpdateText = fUpdateText;
 	fUpdateText = UpdateText();
-	bool updateTextOnOff = fUpdateText == NULL && oldUpdateText != NULL
-		|| fUpdateText != NULL && oldUpdateText == NULL;
+	bool updateTextOnOff = (fUpdateText == NULL && oldUpdateText != NULL)
+		|| (fUpdateText != NULL && oldUpdateText == NULL);
 
 	float newWidth = 0.0;
 	if (fUpdateText != NULL)
diff --git a/src/kits/interface/SplitLayout.cpp b/src/kits/interface/SplitLayout.cpp
index 7f07976dc7..a10b8306e2 100644
--- a/src/kits/interface/SplitLayout.cpp
+++ b/src/kits/interface/SplitLayout.cpp
@@ -563,8 +563,8 @@ BSplitLayout::StartDraggingSplitter(BPoint point)
 
 	// Things shouldn't be draggable, if we have a >= max layout.
 	BSize size = _SubtractInsets(View()->Frame().Size());
-	if (fOrientation == B_HORIZONTAL && size.width >= fMax.width
-		|| fOrientation == B_VERTICAL && size.height >= fMax.height) {
+	if ((fOrientation == B_HORIZONTAL && size.width >= fMax.width)
+		|| (fOrientation == B_VERTICAL && size.height >= fMax.height)) {
 		return false;
 	}
 
@@ -1133,8 +1133,8 @@ void
 BSplitLayout::_InternalGetHeightForWidth(float width, bool realLayout,
 	float* minHeight, float* maxHeight, float* preferredHeight)
 {
-	if (realLayout && fHeightForWidthVerticalLayouterWidth != width
-		|| !realLayout && fCachedHeightForWidthWidth != width) {
+	if ((realLayout && fHeightForWidthVerticalLayouterWidth != width)
+		|| (!realLayout && fCachedHeightForWidthWidth != width)) {
 		// The general strategy is to clone the vertical layouter, which only
 		// knows the general min/max constraints, do a horizontal layout for the
 		// given width, and add the children's height for width constraints to
diff --git a/src/kits/interface/Window.cpp b/src/kits/interface/Window.cpp
index 5d68783f02..f6c79bc22e 100644
--- a/src/kits/interface/Window.cpp
+++ b/src/kits/interface/Window.cpp
@@ -1595,7 +1595,7 @@ void
 BWindow::SetPulseRate(bigtime_t rate)
 {
 	// TODO: What about locking?!?
-	if (rate < 0 || (rate == fPulseRate && !(rate == 0 ^ fPulseRunner == NULL)))
+	if (rate < 0 || (rate == fPulseRate && !((rate == 0) ^ (fPulseRunner == NULL))))
 		return;
 
 	fPulseRate = rate;
diff --git a/src/kits/interface/textview_support/TextGapBuffer.cpp b/src/kits/interface/textview_support/TextGapBuffer.cpp
index 2797a2714f..1310c5c96b 100644
--- a/src/kits/interface/textview_support/TextGapBuffer.cpp
+++ b/src/kits/interface/textview_support/TextGapBuffer.cpp
@@ -172,7 +172,7 @@ TextGapBuffer::SizeGapTo(long inCount)
 const char *
 TextGapBuffer::GetString(int32 fromOffset, int32 *_numBytes)
 {
-	char *result = "";
+	char *result = (char *)"";
 	if (_numBytes == NULL)
 		return result;
 
diff --git a/src/kits/storage/Entry.cpp b/src/kits/storage/Entry.cpp
index fbeb741998..c01420d169 100644
--- a/src/kits/storage/Entry.cpp
+++ b/src/kits/storage/Entry.cpp
@@ -135,8 +135,8 @@ entry_ref::operator==(const entry_ref &ref) const
 	return (device == ref.device
 			&& directory == ref.directory
 			&& (name == ref.name
-				|| name != NULL && ref.name != NULL
-					&& strcmp(name, ref.name) == 0));
+				|| (name != NULL && ref.name != NULL
+					&& strcmp(name, ref.name) == 0)));
 }
 
 /*! \brief Compares the entry_ref with another entry_ref, returning true if they are not equal.
@@ -1095,11 +1095,7 @@ operator<(const entry_ref & a, const entry_ref & b)
 		|| (a.device == b.device
 			&& (a.directory < b.directory
 			|| (a.directory == b.directory
-				&& (a.name == NULL && b.name != NULL
+				&& ((a.name == NULL && b.name != NULL)
 				|| (a.name != NULL && b.name != NULL
 					&& strcmp(a.name, b.name) < 0))))));
 }
-
-
-
-
diff --git a/src/kits/storage/Path.cpp b/src/kits/storage/Path.cpp
index f5844229b9..74a207021f 100644
--- a/src/kits/storage/Path.cpp
+++ b/src/kits/storage/Path.cpp
@@ -390,8 +390,8 @@ BPath::operator==(const BPath &item) const
 bool
 BPath::operator==(const char *path) const
 {
-	return (InitCheck() != B_OK && path == NULL
-			|| fName && path && strcmp(fName, path) == 0);
+	return ((InitCheck() != B_OK && path == NULL)
+			|| (fName != NULL && path != NULL && strcmp(fName, path) == 0));
 }
 
 //! Performs a simple (string-wise) comparison of paths.
diff --git a/src/kits/storage/PathMonitor.cpp b/src/kits/storage/PathMonitor.cpp
index 7be0f2e575..697fdc576b 100644
--- a/src/kits/storage/PathMonitor.cpp
+++ b/src/kits/storage/PathMonitor.cpp
@@ -359,8 +359,8 @@ PathHandler::_EntryCreated(BMessage* message)
 		}
 
 		// a new directory to watch for us
-		if (!entryContained && !_CloserToPath(entry)
-			|| parentContained && !_WatchRecursively()
+		if ((!entryContained && !_CloserToPath(entry))
+			|| (parentContained && !_WatchRecursively())
 			|| _AddDirectory(entry, true) != B_OK
 			|| _WatchFilesOnly())
 			notify = parentContained;
@@ -446,7 +446,7 @@ PathHandler::_EntryMoved(BMessage* message)
 				&& (entryContained || _CloserToPath(entry))) {
 				// there is a new directory to watch for us
 				if (entryContained
-					|| parentContained && !_WatchRecursively()) {
+					|| (parentContained && !_WatchRecursively())) {
 					_AddDirectory(entry, true);
 					// NOTE: entry is toast now!
 				} else if (_GetClosest(fPath.Path(), false,
diff --git a/src/kits/storage/Resources.cpp b/src/kits/storage/Resources.cpp
index 70a9ce0b8f..a5cd00c279 100644
--- a/src/kits/storage/Resources.cpp
+++ b/src/kits/storage/Resources.cpp
@@ -288,10 +288,10 @@ BResources::SetToImage(const void *codeOrDataPointer, bool clobber)
 	int32 cookie = 0;
 
 	while (get_next_image_info(B_CURRENT_TEAM, &cookie, &info) == B_OK) {
-		if ((addr_t)info.text <= address
-				&& address - (addr_t)info.text < (addr_t)info.text_size
-			|| (addr_t)info.data <= address
-				&& address - (addr_t)info.data < (addr_t)info.data_size) {
+		if (((addr_t)info.text <= address
+				&& address - (addr_t)info.text < (addr_t)info.text_size)
+			|| ((addr_t)info.data <= address
+				&& address - (addr_t)info.data < (addr_t)info.data_size)) {
 			return SetTo(info.name, clobber);
 		}
 	}
diff --git a/src/kits/storage/ResourcesContainer.cpp b/src/kits/storage/ResourcesContainer.cpp
index bf903f2b33..34f836d4e1 100644
--- a/src/kits/storage/ResourcesContainer.cpp
+++ b/src/kits/storage/ResourcesContainer.cpp
@@ -143,9 +143,9 @@ ResourcesContainer::IndexOf(type_code type, const char *name) const
 	for (int32 i = 0; index == -1 && i < count; i++) {
 		ResourceItem *item = ResourceAt(i);
 		const char *itemName = item->Name();
-		if (item->Type() == type && (name == NULL && itemName == NULL
-									 || name != NULL && itemName != NULL
-										&& !strcmp(name, itemName))) {
+		if (item->Type() == type && ((name == NULL && itemName == NULL)
+									 || (name != NULL && itemName != NULL
+										&& strcmp(name, itemName) == 0))) {
 			index = i;
 		}
 	}
diff --git a/src/kits/storage/Volume.cpp b/src/kits/storage/Volume.cpp
index 0573556330..2a44c6f846 100644
--- a/src/kits/storage/Volume.cpp
+++ b/src/kits/storage/Volume.cpp
@@ -493,7 +493,7 @@ BVolume::KnowsQuery(void) const
 bool
 BVolume::operator==(const BVolume &volume) const
 {
-	return (InitCheck() != B_OK && volume.InitCheck() != B_OK
+	return ((InitCheck() != B_OK && volume.InitCheck() != B_OK)
 			|| fDevice == volume.fDevice);
 }
 
diff --git a/src/kits/storage/disk_device/Partition.cpp b/src/kits/storage/disk_device/Partition.cpp
index 150f36131c..18d4f29092 100644
--- a/src/kits/storage/disk_device/Partition.cpp
+++ b/src/kits/storage/disk_device/Partition.cpp
@@ -1543,7 +1543,7 @@ BPartition::_SupportsOperation(uint32 flag, uint32 whileMountedFlag,
 bool
 BPartition::_SupportsChildOperation(const BPartition* child, uint32 flag) const
 {
-	if (!fDelegate || child && !child->fDelegate)
+	if (!fDelegate || (child && !child->fDelegate))
 		return false;
 
 	uint32 supported = fDelegate->SupportedChildOperations(
diff --git a/src/kits/storage/sniffer/Parser.cpp b/src/kits/storage/sniffer/Parser.cpp
index 5848de4f94..241df7de91 100644
--- a/src/kits/storage/sniffer/Parser.cpp
+++ b/src/kits/storage/sniffer/Parser.cpp
@@ -260,7 +260,7 @@ TokenStream::SetTo(const std::string &string) {
 		tsssEscapeOneOctal,
 		tsssEscapeTwoOctal,
 		tsssEscapeOneHex,
-	};
+	} TokenStreamScannerState;
 	
 	TokenStreamScannerState state = tsssStart;
 	TokenStreamScannerState escapedState = tsssStart;