From e849b3424a46ac1c742cd5a9340deaaa790f12e3 Mon Sep 17 00:00:00 2001
From: Cheng <zcbenz@gmail.com>
Date: Thu, 21 Mar 2024 13:28:05 +0900
Subject: [PATCH] Do not use static constexpr in header (#863)

Doing so results in each compilation unit (.cpp file) having its own
copy of the variable, while inline constexpr makes sure there is only
one copy.
---
 mlx/dtype.h         | 26 +++++++++++++-------------
 mlx/types/complex.h |  4 ++--
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/mlx/dtype.h b/mlx/dtype.h
index fec1725f3..cb5f79849 100644
--- a/mlx/dtype.h
+++ b/mlx/dtype.h
@@ -46,22 +46,22 @@ struct Dtype {
   };
 };
 
-static constexpr Dtype bool_{Dtype::Val::bool_, sizeof(bool)};
+inline constexpr Dtype bool_{Dtype::Val::bool_, sizeof(bool)};
 
-static constexpr Dtype uint8{Dtype::Val::uint8, sizeof(uint8_t)};
-static constexpr Dtype uint16{Dtype::Val::uint16, sizeof(uint16_t)};
-static constexpr Dtype uint32{Dtype::Val::uint32, sizeof(uint32_t)};
-static constexpr Dtype uint64{Dtype::Val::uint64, sizeof(uint64_t)};
+inline constexpr Dtype uint8{Dtype::Val::uint8, sizeof(uint8_t)};
+inline constexpr Dtype uint16{Dtype::Val::uint16, sizeof(uint16_t)};
+inline constexpr Dtype uint32{Dtype::Val::uint32, sizeof(uint32_t)};
+inline constexpr Dtype uint64{Dtype::Val::uint64, sizeof(uint64_t)};
 
-static constexpr Dtype int8{Dtype::Val::int8, sizeof(int8_t)};
-static constexpr Dtype int16{Dtype::Val::int16, sizeof(int16_t)};
-static constexpr Dtype int32{Dtype::Val::int32, sizeof(int32_t)};
-static constexpr Dtype int64{Dtype::Val::int64, sizeof(int64_t)};
+inline constexpr Dtype int8{Dtype::Val::int8, sizeof(int8_t)};
+inline constexpr Dtype int16{Dtype::Val::int16, sizeof(int16_t)};
+inline constexpr Dtype int32{Dtype::Val::int32, sizeof(int32_t)};
+inline constexpr Dtype int64{Dtype::Val::int64, sizeof(int64_t)};
 
-static constexpr Dtype float16{Dtype::Val::float16, sizeof(uint16_t)};
-static constexpr Dtype float32{Dtype::Val::float32, sizeof(float)};
-static constexpr Dtype bfloat16{Dtype::Val::bfloat16, sizeof(uint16_t)};
-static constexpr Dtype complex64{Dtype::Val::complex64, sizeof(complex64_t)};
+inline constexpr Dtype float16{Dtype::Val::float16, sizeof(uint16_t)};
+inline constexpr Dtype float32{Dtype::Val::float32, sizeof(float)};
+inline constexpr Dtype bfloat16{Dtype::Val::bfloat16, sizeof(uint16_t)};
+inline constexpr Dtype complex64{Dtype::Val::complex64, sizeof(complex64_t)};
 
 Dtype promote_types(const Dtype& t1, const Dtype& t2);
 
diff --git a/mlx/types/complex.h b/mlx/types/complex.h
index 539974d33..dad0b322f 100644
--- a/mlx/types/complex.h
+++ b/mlx/types/complex.h
@@ -10,7 +10,7 @@ struct complex64_t;
 struct complex128_t;
 
 template <typename T>
-static constexpr bool can_convert_to_complex128 =
+inline constexpr bool can_convert_to_complex128 =
     !std::is_same_v<T, complex128_t> && std::is_convertible_v<T, double>;
 
 struct complex128_t : public std::complex<double> {
@@ -28,7 +28,7 @@ struct complex128_t : public std::complex<double> {
 };
 
 template <typename T>
-static constexpr bool can_convert_to_complex64 =
+inline constexpr bool can_convert_to_complex64 =
     !std::is_same_v<T, complex64_t> && std::is_convertible_v<T, float>;
 
 struct complex64_t : public std::complex<float> {