Replace M_LOG2E and M_LN2 with custom macros.

For these to exist we would need to define `_USE_MATH_DEFINES` before
`cmath` or `math.h` is first included.  However, we don't
control the include order for projects outside Eigen, so even defining
the macro in `Eigen/Core` does not fix the issue for projects that
end up including `<cmath>` before Eigen does (explicitly or transitively).

To fix this, we define `EIGEN_LOG2E` and `EIGEN_LN2` ourselves.

1 files changed, 4 insertions, 4 deletions

diff --git a/Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h b/Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h
index 45cc780f1..34e2cb1e7 100644
--- a/Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h
+++ b/Eigen/src/Core/arch/Default/GenericPacketMathFunctions.h
@@ -132,10 +132,10 @@ Packet plog_impl_float(const Packet _x)
 
   // Add the logarithm of the exponent back to the result of the interpolation.
   if (base2) {
-    const Packet cst_log2e = pset1<Packet>(static_cast<float>(M_LOG2E));
+    const Packet cst_log2e = pset1<Packet>(static_cast<float>(EIGEN_LOG2E));
     x = pmadd(x, cst_log2e, e);
   } else {
-    const Packet cst_ln2 = pset1<Packet>(static_cast<float>(M_LN2));
+    const Packet cst_ln2 = pset1<Packet>(static_cast<float>(EIGEN_LN2));
     x = pmadd(e, cst_ln2, x);
   }
 
@@ -253,10 +253,10 @@ Packet plog_impl_double(const Packet _x)
 
   // Add the logarithm of the exponent back to the result of the interpolation.
   if (base2) {
-    const Packet cst_log2e = pset1<Packet>(M_LOG2E);
+    const Packet cst_log2e = pset1<Packet>(EIGEN_LOG2E);
     x = pmadd(x, cst_log2e, e);
   } else {
-    const Packet cst_ln2 = pset1<Packet>(M_LN2);
+    const Packet cst_ln2 = pset1<Packet>(EIGEN_LN2);
     x = pmadd(e, cst_ln2, x);
   }