Fix undefined evaluation order when constructing random vectors

MSVC and GCC evaluate parameters in right-to-left order, whereas Clang
evaluates in left-to-right order, and of course, an optimization could
leave the order of evaluation completely indeterminate.

This commit fixes all instances of the error by explicitly assigning the
results of expressions that use PseudoRandom::next() or range() to their
respective vector components.

The right-to-left evaluation behavior is preserved since Clang is much less
commonly used to compile Minetest than GCC and MSVC combined, and would
therefore cause the least harm.

1 files changed, 27 insertions, 40 deletions

diff --git a/src/cavegen.cpp b/src/cavegen.cpp
index 1beac6f27..5728c1337 100644
--- a/src/cavegen.cpp
+++ b/src/cavegen.cpp
@@ -133,11 +133,9 @@ void CavesRandomWalk::makeCave(MMVManip *vm, v3s16 nmin, v3s16 nmax,
 	route_start_y_max = rangelim(route_start_y_max, route_start_y_min, ar.Y - 1);
 
 	// Randomize starting position
-	orp = v3f(
-		(float)(ps->next() % ar.X) + 0.5,
-		(float)(ps->range(route_start_y_min, route_start_y_max)) + 0.5,
-		(float)(ps->next() % ar.Z) + 0.5
-	);
+	orp.Z = (float)(ps->next() % ar.Z) + 0.5;
+	orp.Y = (float)(ps->range(route_start_y_min, route_start_y_max)) + 0.5;
+	orp.X = (float)(ps->next() % ar.X) + 0.5;
 
 	// Add generation notify begin event
 	if (gennotify) {
@@ -164,11 +162,10 @@ void CavesRandomWalk::makeCave(MMVManip *vm, v3s16 nmin, v3s16 nmax,
 void CavesRandomWalk::makeTunnel(bool dirswitch)
 {
 	if (dirswitch && !large_cave) {
-		main_direction = v3f(
-			((float)(ps->next() % 20) - (float)10) / 10,
-			((float)(ps->next() % 20) - (float)10) / 30,
-			((float)(ps->next() % 20) - (float)10) / 10
-		);
+		main_direction.Z = ((float)(ps->next() % 20) - (float)10) / 10;
+		main_direction.Y = ((float)(ps->next() % 20) - (float)10) / 30;
+		main_direction.X = ((float)(ps->next() % 20) - (float)10) / 10;
+
 		main_direction *= (float)ps->range(0, 10) / 10;
 	}
 
@@ -196,17 +193,13 @@ void CavesRandomWalk::makeTunnel(bool dirswitch)
 	v3f vec;
 	// Jump downward sometimes
 	if (!large_cave && ps->range(0, 12) == 0) {
-		vec = v3f(
-			(float)(ps->next() % (maxlen.X * 1)) - (float)maxlen.X / 2,
-			(float)(ps->next() % (maxlen.Y * 2)) - (float)maxlen.Y,
-			(float)(ps->next() % (maxlen.Z * 1)) - (float)maxlen.Z / 2
-		);
+		vec.Z = (float)(ps->next() % (maxlen.Z * 1)) - (float)maxlen.Z / 2;
+		vec.Y = (float)(ps->next() % (maxlen.Y * 2)) - (float)maxlen.Y;
+		vec.X = (float)(ps->next() % (maxlen.X * 1)) - (float)maxlen.X / 2;
 	} else {
-		vec = v3f(
-			(float)(ps->next() % (maxlen.X * 1)) - (float)maxlen.X / 2,
-			(float)(ps->next() % (maxlen.Y * 1)) - (float)maxlen.Y / 2,
-			(float)(ps->next() % (maxlen.Z * 1)) - (float)maxlen.Z / 2
-		);
+		vec.Z = (float)(ps->next() % (maxlen.Z * 1)) - (float)maxlen.Z / 2;
+		vec.Y = (float)(ps->next() % (maxlen.Y * 1)) - (float)maxlen.Y / 2;
+		vec.X = (float)(ps->next() % (maxlen.X * 1)) - (float)maxlen.X / 2;
 	}
 
 	// Do not make caves that are above ground.
@@ -446,11 +439,9 @@ void CavesV6::makeCave(MMVManip *vm, v3s16 nmin, v3s16 nmax,
 	route_start_y_max = rangelim(route_start_y_max, route_start_y_min, ar.Y - 1);
 
 	// Randomize starting position
-	orp = v3f(
-		(float)(ps->next() % ar.X) + 0.5,
-		(float)(ps->range(route_start_y_min, route_start_y_max)) + 0.5,
-		(float)(ps->next() % ar.Z) + 0.5
-	);
+	orp.Z = (float)(ps->next() % ar.Z) + 0.5;
+	orp.Y = (float)(ps->range(route_start_y_min, route_start_y_max)) + 0.5;
+	orp.X = (float)(ps->next() % ar.X) + 0.5;
 
 	// Add generation notify begin event
 	if (gennotify != NULL) {
@@ -477,11 +468,10 @@ void CavesV6::makeCave(MMVManip *vm, v3s16 nmin, v3s16 nmax,
 void CavesV6::makeTunnel(bool dirswitch)
 {
 	if (dirswitch && !large_cave) {
-		main_direction = v3f(
-			((float)(ps->next() % 20) - (float)10) / 10,
-			((float)(ps->next() % 20) - (float)10) / 30,
-			((float)(ps->next() % 20) - (float)10) / 10
-		);
+		main_direction.Z = ((float)(ps->next() % 20) - (float)10) / 10;
+		main_direction.Y = ((float)(ps->next() % 20) - (float)10) / 30;
+		main_direction.X = ((float)(ps->next() % 20) - (float)10) / 10;
+
 		main_direction *= (float)ps->range(0, 10) / 10;
 	}
 
@@ -506,19 +496,16 @@ void CavesV6::makeTunnel(bool dirswitch)
 		);
 	}
 
-	v3f vec(
-		(float)(ps->next() % maxlen.X) - (float)maxlen.X / 2,
-		(float)(ps->next() % maxlen.Y) - (float)maxlen.Y / 2,
-		(float)(ps->next() % maxlen.Z) - (float)maxlen.Z / 2
-	);
+	v3f vec;
+	vec.Z = (float)(ps->next() % maxlen.Z) - (float)maxlen.Z / 2;
+	vec.Y = (float)(ps->next() % maxlen.Y) - (float)maxlen.Y / 2;
+	vec.X = (float)(ps->next() % maxlen.X) - (float)maxlen.X / 2;
 
 	// Jump downward sometimes
 	if (!large_cave && ps->range(0, 12) == 0) {
-		vec = v3f(
-			(float)(ps->next() % maxlen.X) - (float)maxlen.X / 2,
-			(float)(ps->next() % (maxlen.Y * 2)) - (float)maxlen.Y,
-			(float)(ps->next() % maxlen.Z) - (float)maxlen.Z / 2
-		);
+		vec.Z = (float)(ps->next() % maxlen.Z) - (float)maxlen.Z / 2;
+		vec.Y = (float)(ps->next() % (maxlen.Y * 2)) - (float)maxlen.Y;
+		vec.X = (float)(ps->next() % maxlen.X) - (float)maxlen.X / 2;
 	}
 
 	// Do not make caves that are entirely above ground, to fix shadow bugs