From c0eb5f89a406243f71eae0b705eba4437d9f8565 Mon Sep 17 00:00:00 2001
From: Antonio Sanchez <cantonios@google.com>
Date: Thu, 6 May 2021 19:49:49 -0700
Subject: Restore ABI compatibility for conj with 3.3, fix conflict with boost.

The boost library unfortunately specializes `conj` for various types and
assumes the original two-template-parameter version.  This changes
restores the second parameter.  This also restores ABI compatibility.

The specialization for `std::complex` is because `std::conj` is not
a device function. For custom complex scalar types, users should provide
their own `conj` implementation.

We may consider removing the unnecessary second parameter in the future - but
this will require modifying boost as well.

Fixes #2112.
---
 Eigen/src/Core/MathFunctions.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'Eigen')

diff --git a/Eigen/src/Core/MathFunctions.h b/Eigen/src/Core/MathFunctions.h
index 67b1d8263..f77724052 100644
--- a/Eigen/src/Core/MathFunctions.h
+++ b/Eigen/src/Core/MathFunctions.h
@@ -260,16 +260,17 @@ struct conj_default_impl<Scalar,true>
   }
 };
 
-template<typename Scalar> struct conj_impl : conj_default_impl<Scalar> {};
+template<typename Scalar, bool IsComplex = NumTraits<Scalar>::IsComplex>
+struct conj_impl : conj_default_impl<Scalar, IsComplex> {};
 
 #if defined(EIGEN_GPU_COMPILE_PHASE)
 template<typename T>
-struct conj_impl<std::complex<T> >
+struct conj_impl<std::complex<T>, true>
 {
   EIGEN_DEVICE_FUNC
   static inline std::complex<T> run(const std::complex<T>& x)
   {
-    return std::complex<T>(x.real(), -x.imag());
+    return std::complex<T>(numext::real(x), -numext::imag(x));
   }
 };
 #endif
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