Add more tests for corner cases of log1p and expm1. Add handling of infinite arguments to log1p such that log1p(inf) = inf.

1 files changed, 2 insertions, 1 deletions

diff --git a/Eigen/src/Core/MathFunctions.h b/Eigen/src/Core/MathFunctions.h
index fcf62011e..fbec39d83 100644
--- a/Eigen/src/Core/MathFunctions.h
+++ b/Eigen/src/Core/MathFunctions.h
@@ -551,7 +551,8 @@ namespace std_fallback {
     Scalar x1p = RealScalar(1) + x;
     Scalar log_1p = log(x1p);
     const bool is_small = numext::equal_strict(x1p, Scalar(1));
-    return is_small ? x : x * (log_1p / (x1p - RealScalar(1)));
+    const bool is_inf = numext::equal_strict(x1p, log_1p);
+    return (is_small || is_inf) ? x : x * (log_1p / (x1p - RealScalar(1)));
   }
 }