Fix Lua PcgRandom

Before, this lua code led to a crash: local pcg = PcgRandom(42) local value = pcg:next() This was because if you called s32 PcgRandom::range(min, max) with the minimum and maximum possible values for s32 integers (which the lua binding code did), u32 PcgRandom::range(bound) got called with 0 as the bound. The bound however is one above the maximum value, so 0 is a "special" value to pass to this function. This commit fixes the lua crash by assigning the RNG's full range to the bound 0, which is also fits to the "maximum is bound - 1" principle, as (u32)-1 is the maximum value in the u32 range.
minetest · Aug 12, 2015 · 738fbc6 · 738fbc6
1 parent f0b3252
commit 738fbc6
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diff --git a/src/noise.cpp b/src/noise.cpp
@@ -90,6 +90,9 @@ u32 PcgRandom::next()
 
 u32 PcgRandom::range(u32 bound)
 {
+	// If the bound is 0, we cover the whole RNG's range
+	if (bound == 0)
+		return next();
 	/*
 	If the bound is not a multiple of the RNG's range, it may cause bias,
 	e.g. a RNG has a range from 0 to 3 and we take want a number 0 to 2.

diff --git a/src/unittest/test_random.cpp b/src/unittest/test_random.cpp
@@ -101,6 +101,9 @@ void TestRandom::testPcgRandomRange()
 
 	EXCEPTION_CHECK(PrngException, pr.range(5, 1));
 
+	// Regression test for bug 3027
+	pr.range(pr.RANDOM_MIN, pr.RANDOM_MAX);
+
 	for (u32 i = 0; i != 32768; i++) {
 		int min = (pr.next() % 3000) - 500;
 		int max = (pr.next() % 3000) - 500;