From b1eb757e60c155707b8fc1b2497b632246819c7b Mon Sep 17 00:00:00 2001 From: kwolekr Date: Wed, 11 May 2016 03:47:45 -0400 Subject: 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. --- src/cavegen.cpp | 67 +++++++++++++++++++++++---------------------------------- 1 file changed, 27 insertions(+), 40 deletions(-) (limited to 'src/cavegen.cpp') 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 -- cgit v1.2.3