diff --git a/src/d_net.c b/src/d_net.c
index f8e5ee032..b4e274fc6 100644
--- a/src/d_net.c
+++ b/src/d_net.c
@@ -66,7 +66,7 @@ static INT32 rebound_head, rebound_tail;
 INT32 net_bandwidth;
 
 /// \brief max length per packet
-INT16 hardware_MAXPACKETLENGTH;
+INT16 hardware_MAXPACKETLENGTH = 0;
 
 boolean (*I_NetGet)(void) = NULL;
 void (*I_NetSend)(void) = NULL;
@@ -106,7 +106,7 @@ INT32 ticruned = 0, ticmiss = 0;
 
 // globals
 INT32 getbps, sendbps;
-float lostpercent, duppercent, gamelostpercent;
+float lostpercent = 0.0f, duppercent = 0.0f, gamelostpercent = 0.0f;
 INT32 packetheaderlength;
 
 boolean Net_GetNetStat(void)
diff --git a/src/d_netcmd.c b/src/d_netcmd.c
index cbbb65c02..8759ada88 100644
--- a/src/d_netcmd.c
+++ b/src/d_netcmd.c
@@ -819,7 +819,7 @@ boolean forceresetplayers = false;
 boolean deferencoremode = false;
 UINT8 splitscreen = 0;
 boolean circuitmap = false;
-INT32 adminplayers[MAXPLAYERS];
+INT32 adminplayers[MAXPLAYERS] = {};
 
 #define VOTEROWS ((cv_votemaxrows.value*3) + ((cv_votemaxrows.value > 1) ? (cv_votemaxrows.value - 1) : 0))
 #define VOTEROWSADDSONE ((cv_votemaxrows.value*3) + 1 + ((cv_votemaxrows.value > 1) ? (cv_votemaxrows.value - 1) : 0))
@@ -3284,8 +3284,7 @@ void D_PickVote(void)
 	SendNetXCmd(XD_PICKVOTE, &buf, 2);
 }
 
-static char *
-ConcatCommandArgv (int start, int end)
+static char *ConcatCommandArgv (int start, int end)
 {
 	char *final;
 
diff --git a/src/filesrch.c b/src/filesrch.c
index 7a5b33464..f09c24aab 100644
--- a/src/filesrch.c
+++ b/src/filesrch.c
@@ -49,7 +49,7 @@ size_t menupathindex[menudepth];
 size_t menudepthleft = menudepth;
 
 char menusearchbuf[MAXSTRINGLENGTH+1];
-textinput_t menusearch;
+textinput_t menusearch = {};
 
 char **dirmenu, **coredirmenu; // core only local for this file
 size_t sizedirmenu, sizecoredirmenu; // ditto
@@ -237,10 +237,13 @@ static boolean filemenucmp(char *haystack, char *needle)
 {
 	static char localhaystack[128];
 	strlcpy(localhaystack, haystack, 128);
+
 	if (!cv_addons_search_case.value)
 		strupr(localhaystack);
+
 	if (cv_addons_search_type.value)
-		return (strstr(localhaystack, needle) != 0);
+		return (strstr(localhaystack, needle) != NULL);
+
 	return (!strncmp(localhaystack, needle, menusearch.length));
 }
 
diff --git a/src/g_game.c b/src/g_game.c
index 875deb445..880e555ce 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -174,13 +174,13 @@ UINT16 skincolor_bluering = SKINCOLOR_PERIWINKLE;
 
 boolean exitfadestarted = false;
 
-cutscene_t *cutscenes[128];
+cutscene_t *cutscenes[128] = {};
 textprompt_t *textprompts[MAX_PROMPTS];
 
 INT16 nextmapoverride;
 UINT8 skipstats;
 
-struct quake quake;
+struct quake quake = {};
 
 // Map Header Information
 mapheader_t** mapheaderinfo = {NULL};
@@ -280,7 +280,7 @@ exitcondition_t g_exit;
 fixed_t gravity;
 fixed_t mapobjectscale;
 
-struct maplighting maplighting;
+struct maplighting maplighting = {};
 
 INT16 autobalance; //for CTF team balance
 INT16 teamscramble; //for CTF team scramble
diff --git a/src/g_input.c b/src/g_input.c
index f0d601f67..d4c8f2ba0 100644
--- a/src/g_input.c
+++ b/src/g_input.c
@@ -135,11 +135,11 @@ static void led_off_handle4(void)
 
 // current state of the keys
 // JOYAXISRANGE for fully pressed, 0 for not pressed
-INT32 gamekeydown[MAXDEVICES][NUMINPUTS];
-boolean deviceResponding[MAXDEVICES];
+INT32 gamekeydown[MAXDEVICES][NUMINPUTS] = {};
+boolean deviceResponding[MAXDEVICES] = {false};
 
 // several key codes (or virtual key) per game control
-INT32 gamecontrol[MAXSPLITSCREENPLAYERS][num_gamecontrols][MAXINPUTMAPPING];
+INT32 gamecontrol[MAXSPLITSCREENPLAYERS][num_gamecontrols][MAXINPUTMAPPING] = {};
 
 INT32 gamecontroldefault[num_gamecontrols][MAXINPUTMAPPING] = {
 	[gc_aimforward ] = {KEY_UPARROW,    KEY_AXIS1+2             }, // Left Y-
diff --git a/src/hardware/r_opengl/r_opengl.c b/src/hardware/r_opengl/r_opengl.c
index 3700083e2..099692ea0 100644
--- a/src/hardware/r_opengl/r_opengl.c
+++ b/src/hardware/r_opengl/r_opengl.c
@@ -671,7 +671,7 @@ typedef struct gl_shaderstate_s
 static gl_shaderstate_t gl_shaderstate;
 
 // Shader info
-static float shader_leveltime = 0;
+static float shader_leveltime = 0.0f;
 static float shader_light_x = 0.0f;
 static float shader_light_y = 0.0f;
 static float shader_light_z = 0.0f;
diff --git a/src/i_time.c b/src/i_time.c
index 74380e6f7..f0b2b1ff4 100644
--- a/src/i_time.c
+++ b/src/i_time.c
@@ -21,7 +21,7 @@
 #include "m_fixed.h"
 #include "i_system.h"
 
-timestate_t g_time;
+timestate_t g_time = {};
 
 static CV_PossibleValue_t timescale_cons_t[] = {{FRACUNIT/20, "MIN"}, {20*FRACUNIT, "MAX"}, {0, NULL}};
 consvar_t cv_timescale = CVAR_INIT ("timescale", "1.0", CV_NETVAR|CV_CHEAT|CV_FLOAT, timescale_cons_t, NULL);
diff --git a/src/k_hud.c b/src/k_hud.c
index 6a47c82bc..428db2ed7 100644
--- a/src/k_hud.c
+++ b/src/k_hud.c
@@ -136,7 +136,7 @@ static patch_t *kp_racefinish[6];
 static patch_t *kp_positionnum[NUMPOSNUMS][NUMPOSFRAMES];
 static patch_t *kp_winnernum[NUMPOSFRAMES];
 
-patch_t *kp_facenum[MAXPLAYERS+1];
+patch_t *kp_facenum[MAXPLAYERS+1] = {};
 static patch_t *kp_facehighlight[8];
 
 static patch_t *kp_nocontestminimap;
diff --git a/src/m_cheat.c b/src/m_cheat.c
index f73d42f03..7c2d1abc5 100644
--- a/src/m_cheat.c
+++ b/src/m_cheat.c
@@ -713,7 +713,7 @@ void Command_Resetemeralds_f(void)
 // Devmode
 //
 
-UINT32 cht_debug;
+UINT32 cht_debug = 0;
 
 struct debugFlagNames_s const debug_flag_names[] =
 {
diff --git a/src/m_menu.c b/src/m_menu.c
index bdfee4c42..e460dddc9 100644
--- a/src/m_menu.c
+++ b/src/m_menu.c
@@ -4553,7 +4553,7 @@ INT32 MR_QuitAddons(INT32 choice)
 }
 
 // ---- REPLAY HUT -----
-menudemo_t *demolist;
+menudemo_t *demolist = NULL;
 
 #define DF_ENCORE       0x40
 static INT16 replayScrollTitle = 0;
@@ -5578,7 +5578,7 @@ void M_RefreshPauseMenu(void)
 // SKY ROOM
 // ========
 
-UINT8 skyRoomMenuTranslations[MAXUNLOCKABLES];
+UINT8 skyRoomMenuTranslations[MAXUNLOCKABLES] = {};
 
 static char *M_GetConditionString(condition_t cond)
 {
diff --git a/src/p_maputl.c b/src/p_maputl.c
index 4c89cda17..44fbe9f0f 100644
--- a/src/p_maputl.c
+++ b/src/p_maputl.c
@@ -1490,7 +1490,7 @@ boolean P_BlockThingsIterator(INT32 x, INT32 y, BlockItReturn_t (*func)(mobj_t *
 static intercept_t *intercepts = NULL;
 static intercept_t *intercept_p = NULL;
 
-divline_t g_trace;
+divline_t g_trace = {};
 
 //SoM: 4/6/2000: Remove limit on intercepts.
 static void P_CheckIntercepts(void)
diff --git a/src/p_mobj.c b/src/p_mobj.c
index fb943afb3..2a35f9c72 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -11772,9 +11772,9 @@ void P_RemoveFloorSpriteSlope(mobj_t *mobj)
 //
 // P_RemoveMobj
 //
-mapthing_t *itemrespawnque[ITEMQUESIZE];
-tic_t itemrespawntime[ITEMQUESIZE];
-size_t iquehead, iquetail;
+mapthing_t *itemrespawnque[ITEMQUESIZE] = {};
+tic_t itemrespawntime[ITEMQUESIZE] = {};
+size_t iquehead = 0, iquetail = 0;
 
 #ifdef PARANOIA
 //#define SCRAMBLE_REMOVED // Force debug build to crash when Removed mobj is accessed
diff --git a/src/p_setup.c b/src/p_setup.c
index 5981439db..112378981 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -537,9 +537,9 @@ void P_AllocMapHeader(INT16 i)
 //
 #define MAXLEVELFLATS 256
 
-size_t nummaxflats;
-size_t numlevelflats;
-levelflat_t *levelflats;
+size_t nummaxflats = 0;
+size_t numlevelflats = 0;
+levelflat_t *levelflats = NULL;
 
 //SoM: Other files want this info.
 size_t P_PrecacheLevelFlats(void)
@@ -8148,8 +8148,8 @@ void P_SetupLevelSky(const char *skytexname, boolean global)
 	R_SetupSkyDraw();
 }
 
-static const char *maplumpname;
-lumpnum_t lastloadedmaplumpnum; // for comparative savegame
+static const char *maplumpname = NULL;
+lumpnum_t lastloadedmaplumpnum = LUMPERROR; // for comparative savegame
 
 //
 // P_LevelInitStuff
@@ -8619,7 +8619,7 @@ static void P_InitGametype(void)
 	}
 }
 
-struct minimapinfo minimapinfo;
+struct minimapinfo minimapinfo = {};
 
 static void P_InitMinimapInfo(void)
 {
diff --git a/src/p_user.c b/src/p_user.c
index a5b61fe45..da70f7064 100644
--- a/src/p_user.c
+++ b/src/p_user.c
@@ -2721,7 +2721,7 @@ static void P_DeathThink(player_t *player)
 // P_MoveCamera: make sure the camera is not outside the world and looks at the player avatar
 //
 
-camera_t camera[MAXSPLITSCREENPLAYERS]; // Four cameras, three for splitscreen
+camera_t camera[MAXSPLITSCREENPLAYERS] = {}; // Four cameras, three for splitscreen
 
 static void CV_CamRotate_OnChange(void)
 {
diff --git a/src/r_things.cpp b/src/r_things.cpp
index 24623d6fd..9da9c674d 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -793,7 +793,7 @@ void R_DrawMaskedColumn(drawcolumndata_t* dc, column_t *column, column_t *bright
 	dc->texturemid = basetexturemid;
 }
 
-INT32 lengthcol; // column->length : for flipped column function pointers and multi-patch on 2sided wall = texture->height
+INT32 lengthcol = 0; // column->length : for flipped column function pointers and multi-patch on 2sided wall = texture->height
 
 void R_DrawFlippedMaskedColumn(drawcolumndata_t* dc, column_t *column, column_t *brightmap, INT32 baseclip)
 {
@@ -3992,7 +3992,7 @@ static void R_DrawMaskedList (drawnode_t* head)
 void R_DrawMasked(maskcount_t* masks, INT32 nummasks)
 {
 	ZoneScoped;
-	drawnode_t *heads;	/**< Drawnode lists; as many as number of views/portals. */
+	drawnode_t *heads = NULL;	/**< Drawnode lists; as many as number of views/portals. */
 	INT32 i;
 
 	heads = static_cast<drawnode_t*>(calloc(nummasks, sizeof(drawnode_t)));