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build: MSVC workaround for empty base classes #730

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Merged
merged 1 commit into from
Oct 9, 2025
Merged

build: MSVC workaround for empty base classes #730

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10 changes: 10 additions & 0 deletions src/core/include/mp-units/bits/hacks.h
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,16 @@ MP_UNITS_DIAGNOSTIC_POP

#endif

#if MP_UNITS_COMP_MSVC

#define MP_UNITS_EMPTY_BASES_WORKAROUND __declspec(empty_bases)

#else

#define MP_UNITS_EMPTY_BASES_WORKAROUND

#endif

#if !defined MP_UNITS_API_NO_CRTP && __cpp_explicit_this_parameter

#define MP_UNITS_API_NO_CRTP 1
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6 changes: 4 additions & 2 deletions src/core/include/mp-units/framework/unit.h
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Expand Up @@ -226,7 +226,7 @@ struct propagate_point_origin<U, true> {
};

template<UnitMagnitude auto M, Unit U>
struct scaled_unit_impl : detail::unit_interface, detail::propagate_point_origin<U> {
struct MP_UNITS_EMPTY_BASES_WORKAROUND scaled_unit_impl : detail::unit_interface, detail::propagate_point_origin<U> {
using _base_type_ = scaled_unit_impl; // exposition only
static constexpr UnitMagnitude auto _mag_ = M;
static constexpr U _reference_unit_{};
Expand Down Expand Up @@ -461,7 +461,9 @@ struct common_unit final : decltype(detail::get_common_scaled_unit(U1{}, U2{}, R
namespace detail {

template<typename... Expr>
struct derived_unit_impl : detail::unit_interface, detail::expr_fractions<one, Expr...> {
struct MP_UNITS_EMPTY_BASES_WORKAROUND derived_unit_impl :
detail::unit_interface,
detail::expr_fractions<one, Expr...> {
using _base_type_ = derived_unit_impl; // exposition only
};

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