diff --git a/SConscript b/SConscript
index 8247d5e10..0137e6dac 100644
--- a/SConscript
+++ b/SConscript
@@ -68,7 +68,7 @@ AddSconsOption('opengl-renderer', False, False, "Build with OpenGL renderer supp
 AddSconsOption('renderer', False, False, "Build the save renderer.")
 
 AddSconsOption('wall', False, False, "Error on all warnings.")
-AddSconsOption('no-warnings', True, False, "Disable all compiler warnings (default).")
+AddSconsOption('no-warnings', False, False, "Disable all compiler warnings.")
 AddSconsOption('nolua', False, False, "Disable Lua.")
 AddSconsOption('nofft', False, False, "Disable FFT.")
 AddSconsOption("output", False, True, "Executable output name.")
diff --git a/src/PowderToySDL.cpp b/src/PowderToySDL.cpp
index 78da45825..81f522421 100644
--- a/src/PowderToySDL.cpp
+++ b/src/PowderToySDL.cpp
@@ -948,8 +948,8 @@ int main(int argc, char * argv[])
 			{
 				std::string saveIdPart = "";
 				int saveId;
-				unsigned int hashPos = ptsaveArg.find('#');
-				if(hashPos != std::string::npos)
+				size_t hashPos = ptsaveArg.find('#');
+				if (hashPos != std::string::npos)
 				{
 					saveIdPart = ptsaveArg.substr(7, hashPos-7);
 				}
@@ -957,7 +957,7 @@ int main(int argc, char * argv[])
 				{
 					saveIdPart = ptsaveArg.substr(7);
 				}
-				if(saveIdPart.length())
+				if (saveIdPart.length())
 				{
 #ifdef DEBUG
 					std::cout << "Got Ptsave: id: " <<  saveIdPart << std::endl;
@@ -967,7 +967,7 @@ int main(int argc, char * argv[])
 						throw std::runtime_error("Invalid Save ID");
 
 					SaveInfo * newSave = Client::Ref().GetSave(saveId, 0);
-					if(!newSave)
+					if (!newSave)
 						throw std::runtime_error("Could not load save");
 					GameSave * newGameSave = new GameSave(Client::Ref().GetSaveData(saveId, 0));
 					newSave->SetGameSave(newGameSave);
diff --git a/src/SDLMain.m b/src/SDLMain.m
index 78ef1fe46..63bb32837 100644
--- a/src/SDLMain.m
+++ b/src/SDLMain.m
@@ -395,6 +395,7 @@ void writeUserPreferences(const char * prefData)
     [prefDataNSString release];
 }
 
+//doesn't work on OS X 10.5 or below
 char * readClipboard()
 {
     NSPasteboard *clipboard = [NSPasteboard generalPasteboard];
@@ -416,6 +417,7 @@ char * readClipboard()
     return clipboardDataCopy;
 }
 
+//doesn't work on OS X 10.5 or below
 void writeClipboard(const char * clipboardData)
 {
     NSPasteboard *clipboard = [NSPasteboard generalPasteboard];
diff --git a/src/client/GameSave.cpp b/src/client/GameSave.cpp
index 241f3b451..b85639a79 100644
--- a/src/client/GameSave.cpp
+++ b/src/client/GameSave.cpp
@@ -772,7 +772,7 @@ void GameSave::readOPS(char * data, int dataLength)
 					fanVelY[blockY+y][blockX+x] = (fanData[j++]-127.0f)/64.0f;
 				}
 
-				if (blockMap[y][x] < 0 || blockMap[y][x] >= UI_WALLCOUNT)
+				if (blockMap[y][x] >= UI_WALLCOUNT)
 					blockMap[y][x] = 0;
 			}
 		}
@@ -825,8 +825,6 @@ void GameSave::readOPS(char * data, int dataLength)
 						fprintf(stderr, "Out of range [%d]: %d %d, [%d, %d], [%d, %d]\n", i, x, y, (unsigned)partsData[i+1], (unsigned)partsData[i+2], (unsigned)partsData[i+3], (unsigned)partsData[i+4]);
 						goto fail;
 					}
-					if (partsData[i] >= PT_NUM)
-						partsData[i] = PT_DMND;	//Replace all invalid elements with diamond
 
 					if (newIndex < 0 || newIndex >= NPART)
 						goto fail;
@@ -1295,7 +1293,7 @@ void GameSave::readPSv(char * data, int dataLength)
 						blockMap[y][x]=WL_ALLOWENERGY;
 				}
 
-				if (blockMap[y][x] < 0 || blockMap[y][x] >= UI_WALLCOUNT)
+				if (blockMap[y][x] >= UI_WALLCOUNT)
 					blockMap[y][x] = 0;
 			}
 
diff --git a/src/graphics/Renderer.cpp b/src/graphics/Renderer.cpp
index 5164f4c7c..f40383e73 100644
--- a/src/graphics/Renderer.cpp
+++ b/src/graphics/Renderer.cpp
@@ -201,7 +201,7 @@ void Renderer::clearScreen(float alpha)
 #endif
 }
 #ifdef OGLR
-void Renderer::checkShader(GLuint shader, char * shname)
+void Renderer::checkShader(GLuint shader, const char * shname)
 {
 	GLint status;
 	glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
@@ -214,7 +214,7 @@ void Renderer::checkShader(GLuint shader, char * shname)
 		exit(1);
 	}
 }
-void Renderer::checkProgram(GLuint program, char * progname)
+void Renderer::checkProgram(GLuint program, const char * progname)
 {
 	GLint status;
 	glGetProgramiv(program, GL_LINK_STATUS, &status);
@@ -706,7 +706,7 @@ void Renderer::DrawWalls()
 			if (bmap[y][x])
 			{
 				wt = bmap[y][x];
-				if (wt<0 || wt>=UI_WALLCOUNT)
+				if (wt >= UI_WALLCOUNT)
 					continue;
 				pc = wtypes[wt].colour;
 				gc = wtypes[wt].eglow;
diff --git a/src/graphics/Renderer.h b/src/graphics/Renderer.h
index 574ab072c..3f1392b86 100644
--- a/src/graphics/Renderer.h
+++ b/src/graphics/Renderer.h
@@ -99,8 +99,8 @@ public:
 	void SetSample(int x, int y);
 
 #ifdef OGLR
-	void checkShader(GLuint shader, char * shname);
-	void checkProgram(GLuint program, char * progname);
+	void checkShader(GLuint shader, const char * shname);
+	void checkProgram(GLuint program, const char * progname);
 	void loadShaders();
 	GLuint vidBuf,textTexture;
 	GLint prevFbo;
diff --git a/src/simulation/Simulation.cpp b/src/simulation/Simulation.cpp
index 36f52feca..3a6eac3db 100644
--- a/src/simulation/Simulation.cpp
+++ b/src/simulation/Simulation.cpp
@@ -81,8 +81,10 @@ int Simulation::Load(int fullX, int fullY, GameSave * save)
 		x = int(tempPart.x + 0.5f);
 		y = int(tempPart.y + 0.5f);
 
-		if(tempPart.type >= 0 && tempPart.type < PT_NUM)
+		if (tempPart.type >= 0 && tempPart.type < PT_NUM)
 			tempPart.type = partMap[tempPart.type];
+		else
+			continue;
 
 		if ((player.spwn == 1 && tempPart.type==PT_STKM) || (player2.spwn == 1 && tempPart.type==PT_STKM2))
 			continue;