[hist] Prevent out-of-bounds in RRegularAxis

Author: hahnjo

hist/histv7/inc/ROOT/RRegularAxis.hxx

@@ -101,6 +101,9 @@ public:
       }
 
       std::size_t bin = (x - fLow) * fInvBinWidth;
+      if (bin >= fNNormalBins) {
+         bin = fNNormalBins - 1;
+      }
       return {bin, true};
    }
 

hist/histv7/test/hist_regular.cxx

@@ -113,6 +113,16 @@ TEST(RRegularAxis, ComputeLinearizedIndex)
    }
 }
 
+TEST(RRegularAxis, ComputeLinearizedIndexMin)
+{
+   static constexpr std::size_t Bins = 20;
+   const RRegularAxis axis(Bins, {-1, std::numeric_limits<double>::min()});
+
+   auto linIndex = axis.ComputeLinearizedIndex(0);
+   EXPECT_EQ(linIndex.fIndex, Bins - 1);
+   EXPECT_TRUE(linIndex.fValid);
+}
+
 TEST(RRegularAxis, GetLinearizedIndex)
 {
    static constexpr std::size_t Bins = 20;