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Fix undefined evaluation order when constructing random vectors

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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.
This commit is contained in:
kwolekr 2016-05-11 03:47:45 -04:00
parent 5b05f75a27
commit b1eb757e60
2 changed files with 47 additions and 49 deletions
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67
src/cavegen.cpp
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@ -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