fix undefined behaviour in various places

these were found by UBSan in clang builds. they don't show up in gcc
builds

src/boss.c

@@ -195,6 +195,10 @@ void draw_boss(Boss *boss) {
 			hpspan += boss->attacks[prevspell].hp;
 		}
 
+		if(!maxhpspan) {
+			return;
+		}
+
 		glPushMatrix();
 		glTranslatef(10,2,0);
 		glScalef((VIEWPORT_W-60)/(float)maxhpspan,1,1);

src/color.c

@@ -12,16 +12,25 @@
 static const float conv = 1.0f / CLR_ONEVALUE;
 
 Color rgba(float r, float g, float b, float a) {
-    return ((((Color)(CLR_ONEVALUE * (r)) & CLR_CMASK) << CLR_R) + \
-            (((Color)(CLR_ONEVALUE * (g)) & CLR_CMASK) << CLR_G) + \
-            (((Color)(CLR_ONEVALUE * (b)) & CLR_CMASK) << CLR_B) + \
-            (((Color)(CLR_ONEVALUE * (a)) & CLR_CMASK) << CLR_A));
+    assert(!r || isnormal(r));
+    assert(!g || isnormal(g));
+    assert(!b || isnormal(b));
+    assert(!a || isnormal(a));
+
+    return ((((Color)(ColorComponent)(CLR_ONEVALUE * (r)) & CLR_CMASK) << CLR_R) + \
+            (((Color)(ColorComponent)(CLR_ONEVALUE * (g)) & CLR_CMASK) << CLR_G) + \
+            (((Color)(ColorComponent)(CLR_ONEVALUE * (b)) & CLR_CMASK) << CLR_B) + \
+            (((Color)(ColorComponent)(CLR_ONEVALUE * (a)) & CLR_CMASK) << CLR_A));
 }
 
 Color rgb(float r, float g, float b) {
-    return ((((Color)(CLR_ONEVALUE * (r)) & CLR_CMASK) << CLR_R) + \
-            (((Color)(CLR_ONEVALUE * (g)) & CLR_CMASK) << CLR_G) + \
-            (((Color)(CLR_ONEVALUE * (b)) & CLR_CMASK) << CLR_B) + \
+    assert(!r || isnormal(r));
+    assert(!g || isnormal(g));
+    assert(!b || isnormal(b));
+
+    return ((((Color)(ColorComponent)(CLR_ONEVALUE * (r)) & CLR_CMASK) << CLR_R) + \
+            (((Color)(ColorComponent)(CLR_ONEVALUE * (g)) & CLR_CMASK) << CLR_G) + \
+            (((Color)(ColorComponent)(CLR_ONEVALUE * (b)) & CLR_CMASK) << CLR_B) + \
             (CLR_ONEVALUE << CLR_A));
 }
 

src/laser.c

@@ -233,6 +233,10 @@ int collision_line(complex a, complex b, complex c, float r) {
 	la = a*conj(a);
 	lm = m*conj(m);
 
+	if(!lm) {
+		return 0;
+	}
+
 	d = -(creal(a)*creal(m)+cimag(a)*cimag(m))/lm;
 
 	s = d*d - (la - r*r)/lm;

src/menu/mainmenu.c

@@ -173,9 +173,15 @@ void draw_main_menu(MenuData *menu) {
 		float ry = sin(913*i+137*cycle);
 		float rz = sin(1303*i+89631*cycle);
 		float r = sqrt(rx*rx+ry*ry+rz*rz);
+
+		if(!r) {
+			continue;
+		}
+
 		rx /= r;
 		ry /= r;
 		rz /= r;
+
 		if(posx > SCREEN_W+20 || posy < -20 || posy > SCREEN_H+20)
 			continue;
 

src/stagedraw.c

@@ -229,7 +229,7 @@ static void stage_draw_objects(void) {
 
 		if(boss_is_dying(global.boss)) {
 			float t = (global.frames - global.boss->current->endtime)/(float)BOSS_DEATH_DELAY + 1;
-			f -= t*(t-0.7)/(1-t);
+			f -= t*(t-0.7)/max(0.01, 1-t);
 		}
 
 		glScalef(f,f,f);

src/stages/stage3_events.c

@@ -680,6 +680,10 @@ void stage3_boss_a2_warnlaser_logic(Laser *l, int time) {
 		return;
 	}
 
+	if(time < 0) {
+		return;
+	}
+
 	l->width = laser_charge(l, time, 90, 10);
 	l->color = mix_colors(rgb(1, 0.2, 0.2), rgb(0.2, 0.2, 1), time / l->deathtime);
 }

src/util.c

@@ -278,7 +278,7 @@ void limit_frame_rate(uint64_t *lasttime) {
     }
 
     double passed = (double)(SDL_GetPerformanceCounter() - *lasttime) / SDL_GetPerformanceFrequency();
-    double delay = 1.0 / FPS - passed;
+    double delay = max(0, 1.0 / FPS - passed);
     uint32_t delay_ms = (uint32_t)(delay * 1000.0);
 
     if(delay > 0 && delay_ms > 0) {