diff --git a/lzma/C/LzmaEnc.c b/lzma/C/LzmaEnc.c
index da39520c65..870399d35a 100644
--- a/lzma/C/LzmaEnc.c
+++ b/lzma/C/LzmaEnc.c
@@ -2086,7 +2086,7 @@ void LzmaEnc_Finish(CLzmaEncHandle pp)
   if (p->mtMode)
     MatchFinderMt_ReleaseStream(&p->matchFinderMt);
   #else
-  pp = pp;
+    (void)pp;
   #endif
 }
 
diff --git a/src/actor.h b/src/actor.h
index b7a8614a74..78c82066c1 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -845,7 +845,8 @@ public:
 	DWORD			fillcolor;			// Color to draw when STYLE_Shaded
 
 // interaction info
-	fixed_t			pitch, roll;
+	fixed_t			pitch;
+	angle_t			roll;	// This was fixed_t before, which is probably wrong
 	FBlockNode		*BlockNode;			// links in blocks (if needed)
 	struct sector_t	*Sector;
 	subsector_t *		subsector;
diff --git a/src/b_func.cpp b/src/b_func.cpp
index 1c29c2cf63..2800c01c5d 100644
--- a/src/b_func.cpp
+++ b/src/b_func.cpp
@@ -123,7 +123,7 @@ bool DBot::Check_LOS (AActor *to, angle_t vangle)
 	if (vangle == 0)
 		return false; //Looker seems to be blind.
 
-	return (angle_t)abs (R_PointToAngle2 (player->mo->x, player->mo->y, to->x, to->y) - player->mo->angle) <= vangle/2;
+	return absangle(R_PointToAngle2 (player->mo->x, player->mo->y, to->x, to->y) - player->mo->angle) <= vangle/2;
 }
 
 //-------------------------------------
@@ -210,7 +210,7 @@ void DBot::Dofire (ticcmd_t *cmd)
 			{
 				angle = an;
 				//have to be somewhat precise. to avoid suicide.
-				if (abs (angle - player->mo->angle) < 12*ANGLE_1)
+				if (absangle(angle - player->mo->angle) < 12*ANGLE_1)
 				{
 					t_rocket = 9;
 					no_fire = false;
@@ -252,7 +252,7 @@ shootmissile:
 				angle -= m;
 		}
 
-		if (abs (angle - player->mo->angle) < 4*ANGLE_1)
+		if (absangle(angle - player->mo->angle) < 4*ANGLE_1)
 		{
 			increase = !increase;
 		}
diff --git a/src/d_net.cpp b/src/d_net.cpp
index 9ab4b61799..bc5ccdba95 100644
--- a/src/d_net.cpp
+++ b/src/d_net.cpp
@@ -230,7 +230,7 @@ static struct TicSpecial
 
 		specialsize = MAX(specialsize * 2, needed + 30);
 
-		DPrintf ("Expanding special size to %d\n", specialsize);
+		DPrintf ("Expanding special size to %zu\n", specialsize);
 
 		for (i = 0; i < BACKUPTICS; i++)
 			streams[i] = (BYTE *)M_Realloc (streams[i], specialsize);
diff --git a/src/g_game.cpp b/src/g_game.cpp
index 007604a1cb..c442ee8751 100644
--- a/src/g_game.cpp
+++ b/src/g_game.cpp
@@ -1020,11 +1020,11 @@ void G_Ticker ()
 	{
 		if (playeringame[i])
 		{
-			if ((players[i].playerstate == PST_GONE))
+			if (players[i].playerstate == PST_GONE)
 			{
 				G_DoPlayerPop(i);
 			}
-			if ((players[i].playerstate == PST_REBORN || players[i].playerstate == PST_ENTER))
+			if (players[i].playerstate == PST_REBORN || players[i].playerstate == PST_ENTER)
 			{
 				G_DoReborn(i, false);
 			}
diff --git a/src/g_hexen/a_dragon.cpp b/src/g_hexen/a_dragon.cpp
index 22c92b4d72..fdf2428afe 100644
--- a/src/g_hexen/a_dragon.cpp
+++ b/src/g_hexen/a_dragon.cpp
@@ -78,8 +78,8 @@ static void DragonSeek (AActor *actor, angle_t thresh, angle_t turnMax)
 	if (target->flags&MF_SHOOTABLE && pr_dragonseek() < 64)
 	{ // attack the destination mobj if it's attackable
 		AActor *oldTarget;
-	
-		if (abs(actor->angle-R_PointToAngle2(actor->x, actor->y, 
+
+		if (absangle(actor->angle-R_PointToAngle2(actor->x, actor->y,
 			target->x, target->y)) < ANGLE_45/2)
 		{
 			oldTarget = actor->target;
@@ -121,9 +121,9 @@ static void DragonSeek (AActor *actor, angle_t thresh, angle_t turnMax)
 				}
 				angleToSpot = R_PointToAngle2(actor->x, actor->y, 
 					mo->x, mo->y);
-				if ((angle_t)abs(angleToSpot-angleToTarget) < bestAngle)
+				if (absangle(angleToSpot-angleToTarget) < bestAngle)
 				{
-					bestAngle = abs(angleToSpot-angleToTarget);
+					bestAngle = absangle(angleToSpot-angleToTarget);
 					bestActor = mo;
 				}
 			}
@@ -198,14 +198,14 @@ DEFINE_ACTION_FUNCTION(AActor, A_DragonFlight)
 		}
 		angle = R_PointToAngle2(self->x, self->y, self->target->x,
 			self->target->y);
-		if (abs(self->angle-angle) < ANGLE_45/2 && self->CheckMeleeRange())
+		if (absangle(self->angle-angle) < ANGLE_45/2 && self->CheckMeleeRange())
 		{
 			int damage = pr_dragonflight.HitDice (8);
 			int newdam = P_DamageMobj (self->target, self, self, damage, NAME_Melee);
 			P_TraceBleed (newdam > 0 ? newdam : damage, self->target, self);
 			S_Sound (self, CHAN_WEAPON, self->AttackSound, 1, ATTN_NORM);
 		}
-		else if (abs(self->angle-angle) <= ANGLE_1*20)
+		else if (absangle(self->angle-angle) <= ANGLE_1*20)
 		{
 			self->SetState (self->MissileState);
 			S_Sound (self, CHAN_WEAPON, self->AttackSound, 1, ATTN_NORM);
diff --git a/src/g_hexen/a_heresiarch.cpp b/src/g_hexen/a_heresiarch.cpp
index 15e6da9c18..9ca0a70e80 100644
--- a/src/g_hexen/a_heresiarch.cpp
+++ b/src/g_hexen/a_heresiarch.cpp
@@ -314,7 +314,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_SorcBallOrbit)
 	case SORC_STOPPING:			// Balls stopping
 		if ((parent->StopBall == RUNTIME_TYPE(actor)) &&
 			 (parent->args[1] > SORCBALL_SPEED_ROTATIONS) &&
-			 (abs(angle - (parent->angle>>ANGLETOFINESHIFT)) < (30<<5)))
+			 (absangle(angle - (parent->angle>>ANGLETOFINESHIFT)) < (30<<5)))
 		{
 			// Can stop now
 			actor->target->args[3] = SORC_FIRESPELL;
diff --git a/src/g_hexen/a_hexenspecialdecs.cpp b/src/g_hexen/a_hexenspecialdecs.cpp
index 5485d8d1f2..9d0c098fe4 100644
--- a/src/g_hexen/a_hexenspecialdecs.cpp
+++ b/src/g_hexen/a_hexenspecialdecs.cpp
@@ -109,14 +109,14 @@ DEFINE_ACTION_FUNCTION(AActor, A_PotteryCheck)
 		if (playeringame[i])
 		{
 			AActor *pmo = players[i].mo;
-			if (P_CheckSight (self, pmo) && (abs (R_PointToAngle2 (pmo->x,
+			if (P_CheckSight (self, pmo) && (absangle(R_PointToAngle2 (pmo->x,
 				pmo->y, self->x, self->y) - pmo->angle) <= ANGLE_45))
 			{ // Previous state (pottery bit waiting state)
 				self->SetState (self->state - 1);
 				return;
 			}
 		}
-	}		
+	}
 }
 
 // Lynched corpse (no heart) ------------------------------------------------
diff --git a/src/p_enemy.cpp b/src/p_enemy.cpp
index 24a8506148..55b49b65ed 100644
--- a/src/p_enemy.cpp
+++ b/src/p_enemy.cpp
@@ -2754,7 +2754,7 @@ void A_Face (AActor *self, AActor *other, angle_t max_turn, angle_t max_pitch, a
 
 	// 0 means no limit. Also, if we turn in a single step anyways, no need to go through the algorithms.
 	// It also means that there is no need to check for going past the other.
-	if (max_turn && (max_turn < (angle_t)abs(self->angle - other_angle)))
+	if (max_turn && (max_turn < absangle(self->angle - other_angle)))
 	{
 		if (self->angle > other_angle)
 		{
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 0137ce9e09..608ecb4072 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -2951,7 +2951,7 @@ bool AActor::AdjustReflectionAngle (AActor *thing, angle_t &angle)
 	if (thing->flags4&MF4_SHIELDREFLECT)
 	{
 		// Shield reflection (from the Centaur
-		if (abs (angle - thing->angle)>>24 > 45)
+		if (absangle(angle - thing->angle)>>24 > 45)
 			return true;	// Let missile explode
 
 		if (thing->IsKindOf (RUNTIME_CLASS(AHolySpirit)))	// shouldn't this be handled by another flag???
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index c0810cc291..e374f0249e 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -1311,7 +1311,7 @@ void P_LoadSegs (MapData * map)
 
 			ptp_angle = R_PointToAngle2 (li->v1->x, li->v1->y, li->v2->x, li->v2->y);
 			dis = 0;
-			delta_angle = (abs(ptp_angle-(segangle<<16))>>ANGLETOFINESHIFT)*360/FINEANGLES;
+			delta_angle = (absangle(ptp_angle-(segangle<<16))>>ANGLETOFINESHIFT)*360/FINEANGLES;
 
 			if (delta_angle != 0)
 			{
diff --git a/src/r_data/colormaps.h b/src/r_data/colormaps.h
index 81f9080e0c..f3a2ad9ff5 100644
--- a/src/r_data/colormaps.h
+++ b/src/r_data/colormaps.h
@@ -56,13 +56,13 @@ extern TArray<FSpecialColormap> SpecialColormaps;
 // some utility functions to store special colormaps in powerup blends
 #define SPECIALCOLORMAP_MASK 0x00b60000
 
-inline int MakeSpecialColormap(int index)
+inline uint32 MakeSpecialColormap(int index)
 {
 	assert(index >= 0 && index < 65536);
 	return index | SPECIALCOLORMAP_MASK;
 }
 
-inline bool IsSpecialColormap(int map)
+inline bool IsSpecialColormap(uint32 map)
 {
 	return (map & 0xFFFF0000) == SPECIALCOLORMAP_MASK;
 }
@@ -86,4 +86,4 @@ extern bool NormalLightHasFixedLights;
 FDynamicColormap *GetSpecialLights (PalEntry lightcolor, PalEntry fadecolor, int desaturate);
 
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/tables.h b/src/tables.h
index 04a66376e6..dbe9af0c17 100644
--- a/src/tables.h
+++ b/src/tables.h
@@ -36,6 +36,7 @@
 #ifndef __TABLES_H__
 #define __TABLES_H__
 
+#include <stdlib.h>
 #include <math.h>
 #include "basictypes.h"
 
@@ -92,14 +93,15 @@ extern fixed_t			finetangent[FINEANGLES/2];
 
 typedef uint32			angle_t;
 
-// Avoid "ambiguous call to overloaded function" errors
-// Only to be used when you have subtracted two angles.
-#ifndef __GNUC__
-inline angle_t abs (angle_t ang)
+// Previously seen all over the place, code like this:  abs(ang1 - ang2)
+// Clang warns (and is absolutely correct) that technically, this
+// could be optimized away and do nothing:
+//   warning: taking the absolute value of unsigned type 'unsigned int' has no effect
+//   note: remove the call to 'abs' since unsigned values cannot be negative
+inline angle_t absangle(angle_t a)
 {
-	return (angle_t)abs((SDWORD)ang);
+	return (angle_t)abs((int32)a);
 }
-#endif
 
 // Effective size is 2049;
 // The +1 size is to handle the case when x==y
diff --git a/tools/zipdir/zipdir.c b/tools/zipdir/zipdir.c
index 1479952e09..db6a57e1ef 100644
--- a/tools/zipdir/zipdir.c
+++ b/tools/zipdir/zipdir.c
@@ -871,8 +871,8 @@ int append_to_zip(FILE *zip_file, file_sorted_t *filep, FILE *ozip, BYTE *odir)
 	LocalFileHeader local;
 	uLong crc;
 	file_entry_t *file;
-	char *readbuf;
-	char *compbuf[2];
+	Byte *readbuf;
+	Byte *compbuf[2];
 	unsigned int comp_len[2];
 	int offset[2];
 	int method[2];
@@ -937,7 +937,7 @@ int append_to_zip(FILE *zip_file, file_sorted_t *filep, FILE *ozip, BYTE *odir)
 	if (odir != NULL && ozip != NULL)
 	{
 		CentralDirectoryEntry *dirent;
-		
+
 		dirent = find_file_in_zip(odir, filep->path_in_zip, len, crc, file->date, file->time);
 		if (dirent != NULL)
 		{
@@ -1256,7 +1256,7 @@ int compress_lzma(Byte *out, unsigned int *outlen, const Byte *in, unsigned int
 
 int compress_bzip2(Byte *out, unsigned int *outlen, const Byte *in, unsigned int inlen)
 {
-	if (BZ_OK == BZ2_bzBuffToBuffCompress(out, outlen, (char *)in, inlen, 9, 0, 0))
+	if (BZ_OK == BZ2_bzBuffToBuffCompress((char *)out, outlen, (char *)in, inlen, 9, 0, 0))
 	{
 		return 0;
 	}
@@ -1525,7 +1525,7 @@ int copy_zip_file(FILE *zip, file_entry_t *file, FILE *ozip, CentralDirectoryEnt
 		return 0;
 	}
 	// Check to be sure name matches.
-	if (strncmp(buf, (char *)(ent + 1), LittleShort(lfh.NameLength)) != 0)
+	if (strncmp((char *)buf, (char *)(ent + 1), LittleShort(lfh.NameLength)) != 0)
 	{
 		free(buf);
 		return 0;