- Fix most GCC warnings in the backend/common code code.

* Most of them were just signedness issues. Hopefully I got everything right here.
* 3rd party stuff deliberately not touched.

source/common/console/c_dispatch.cpp

@@ -209,7 +209,7 @@ void C_DoCommand (const char *cmd, int keynum)
 	else
 	{
 		beg = cmd;
-		for (end = cmd+1; *end > ' ' || *end < 0; ++end)
+		for (end = cmd+1; *end > ' ' || (signed char)(*end) < 0; ++end)
 			;
 	}
 

source/common/filesystem/source/file_whres.cpp

@@ -91,8 +91,8 @@ bool FWHResFile::Open(LumpFilterInfo*)
 		uint32_t offset = LittleLong(directory[k*3]) * 4096;
 		uint32_t length = LittleLong(directory[k*3+1]);
 		if (length == 0) break;
-		char num[5];
+		char num[6];
-		snprintf(num, 5, "/%04d", k);
+		snprintf(num, 6, "/%04d", k);
 		std::string synthname = BaseName;
 		synthname += num;
 		Lumps[i].LumpNameSetup(synthname.c_str(), stringpool);

source/common/filesystem/source/file_zip.cpp

@@ -297,7 +297,7 @@ bool FZipFile::Open(LumpFilterInfo* filter, FileSystemMessageFunc Printf)
 			// at least one of the more common definition lumps must be present.
 			for (auto &p : filter->requiredPrefixes)
 			{ 
-				if (name.find(name0 + p) == 0 || name.rfind(p) == ptrdiff_t(name.length() - p.length()))
+				if (name.find(name0 + p) == 0 || name.rfind(p) == size_t(name.length() - p.length()))
 				{
 					foundspeciallump = true;
 					break;

source/common/filesystem/source/files_decompress.cpp

@@ -173,7 +173,7 @@ public:
 
 	ptrdiff_t Read (void *buffer, ptrdiff_t len) override
 	{
-		int err;
+		int err = 0;
 
 		if (File == nullptr)
 		{

source/common/filesystem/source/filesystem.cpp

@@ -147,7 +147,7 @@ struct FileSystem::LumpRecord
 			{
 				std::string longName = LongName;
 				ptrdiff_t encodedResID = longName.find_last_of(".{");
-				if (resourceId == -1 && encodedResID != std::string::npos)
+				if (resourceId == -1 && (size_t)encodedResID != std::string::npos)
 				{
 					const char* p = LongName + encodedResID;
 					char* q;
@@ -978,7 +978,7 @@ void FileSystem::MoveLumpsInFolder(const char *path)
 
 int FileSystem::FindLump (const char *name, int *lastlump, bool anyns)
 {
-	if (*lastlump >= FileInfo.size()) return -1;
+	if ((size_t)*lastlump >= FileInfo.size()) return -1;
 	union
 	{
 		char name8[8];

source/common/filesystem/source/resourcefile.cpp

@@ -415,7 +415,7 @@ void FResourceFile::PostProcessArchive(void *lumps, size_t lumpsize, LumpFilterI
 	ptrdiff_t lastpos = -1;
 	std::string file;
 	std::string& LumpFilter = filter->dotFilter;
-	while ((len = LumpFilter.find_first_of('.', lastpos+1)) != LumpFilter.npos)
+	while (size_t(len = LumpFilter.find_first_of('.', lastpos+1)) != LumpFilter.npos)
 	{
 		max -= FilterLumps(std::string(LumpFilter, 0, len), lumps, lumpsize, max);
 		lastpos = len;

source/common/textures/animlib.cpp

@@ -222,7 +222,7 @@ int32_t ANIM_LoadAnim(anim_t *anim, const uint8_t *buffer, size_t length)
 	if (memcmp(buffer, "LPF ", 4)) return -1;
 
 	length -= sizeof(lpfileheader)+128+768;
-	if (length < 0)
+	if ((signed)length < 0)
 		return -1;
 
 	anim->curlpnum = 0xffff;
@@ -244,7 +244,7 @@ int32_t ANIM_LoadAnim(anim_t *anim, const uint8_t *buffer, size_t length)
 	lpheader.framesPerSecond = LittleShort(lpheader.framesPerSecond);
 
 	length -= lpheader.nLps * sizeof(lp_descriptor);
-	if (length < 0)
+	if ((signed)length < 0)
 		return -2;
 
 	buffer += sizeof(lpfileheader)+128;

source/common/textures/formats/qoitexture.cpp

@@ -59,7 +59,7 @@ FImageSource *QOIImage_TryCreate(FileReader &file, int lumpnum)
 {
 	QOIHeader header;
 
-	if (file.GetLength() < (sizeof(header) + 8))
+	if ((size_t)file.GetLength() < (sizeof(header) + 8))
 	{
 		return nullptr;
 	}
@@ -86,7 +86,7 @@ FQOITexture::FQOITexture(int lumpnum, QOIHeader& header)
 	LeftOffset = TopOffset = 0;
 	Width = header.width;
 	Height = header.height;
-	if (header.channels == 3) bMasked = bTranslucent = false;
+	if (header.channels == 3) bMasked = (bTranslucent = false);
 }
 
 PalettedPixels FQOITexture::CreatePalettedPixels(int conversion, int frame)

source/common/textures/texturemanager.cpp

@@ -1632,7 +1632,7 @@ void FTextureManager::Listaliases()
 
 void FTextureManager::SetLinkedTexture(int lump, FGameTexture* tex)
 {
-	if ((size_t)lump < fileSystem.GetNumEntries())
+	if (lump < fileSystem.GetNumEntries())
 	{
 		linkedMap.Insert(lump, tex);
 	}
@@ -1646,7 +1646,7 @@ void FTextureManager::SetLinkedTexture(int lump, FGameTexture* tex)
 
 FGameTexture* FTextureManager::GetLinkedTexture(int lump)
 {
-	if ((size_t)lump < fileSystem.GetNumEntries())
+	if (lump < fileSystem.GetNumEntries())
 	{
 		auto check = linkedMap.CheckKey(lump);
 		if (check) return *check;

source/common/utility/zstring.cpp

@@ -842,12 +842,12 @@ void FString::StripLeftRight ()
 	if (max == 0) return;
 	for (i = 0; i < max; ++i)
 	{
-		if (Chars[i] < 0 || !isspace((unsigned char)Chars[i]))
+		if ((signed char)Chars[i] < 0 || !isspace((unsigned char)Chars[i]))
 			break;
 	}
 	for (j = max - 1; j >= i; --j)
 	{
-		if (Chars[j] < 0 || !isspace((unsigned char)Chars[j]))
+		if ((signed char)Chars[j] < 0 || !isspace((unsigned char)Chars[j]))
 			break;
 	}
 	if (i == 0 && j == max - 1)

source/core/gamefuncs.cpp

@@ -1285,7 +1285,7 @@ int FindBestSector(const DVector3& pos)
 
 int isAwayFromWall(DCoreActor* ac, double delta)
 {
-	sectortype* s1;
+	sectortype* s1 = nullptr;
 
 	updatesector(ac->spr.pos + DVector2(delta, delta), &s1);
 	if (s1 == ac->sector())

source/core/vmexports.cpp

@@ -800,7 +800,7 @@ void tspritetype_setSpritePic(tspritetype* targ, DCoreActor* self, unsigned z)
 	{
 		targ->setspritetexture(spriteset[z]);
 	}
-	else if (z == ~0)
+	else if ((signed)z == ~0)
 	{
 		targ->setspritetexture(self->dispictex);
 	}