Adding constexpr qualifier for helper functions #1050 (#1184)

* Adding constexpr for exterior product

* Adding constexpr for conjugate

* Adding constexpr for dot, cross and inverse quaternion functions

* Adding constexpr for quat lerp

* Adding constexpr to quaternion comparison functions

lessThan, lessThanEqual, greaterThan, greaterThanEqual

* Adding constexpr for mix functions

mix(scalar, scalar), mix(vec, vec, vec), mix(vec,vec,scalar)

* Adding constexpr for sign(vec) and sign(genFIType)

* Initialize result lessThan, lessThanEqual, greaterThan, greaterThanEqual

Default ctor used in constexpr contex generates warning on gcc

* Adding constexpr to cross(vec, qua) and cross(qua, vec)

* Adding constexpr to glm::translate

* Adding constexpr for exterior product

* Adding constexpr for conjugate

* Adding constexpr for dot, cross and inverse quaternion functions

* Adding constexpr for quat lerp

* Adding constexpr to quaternion comparison functions

lessThan, lessThanEqual, greaterThan, greaterThanEqual

* Adding constexpr for mix functions

mix(scalar, scalar), mix(vec, vec, vec), mix(vec,vec,scalar)

* Adding constexpr for sign(vec) and sign(genFIType)

* Initialize result lessThan, lessThanEqual, greaterThan, greaterThanEqual

Default ctor used in constexpr contex generates warning on gcc

* Adding constexpr to cross(vec, qua) and cross(qua, vec)

* Adding constexpr to glm::translate

---------

Co-authored-by: RohacekD <[email protected]>

glm/common.hpp

@@ -51,7 +51,7 @@ namespace glm
 	/// @see <a href="http://www.opengl.org/sdk/docs/manglsl/xhtml/sign.xml">GLSL sign man page</a>
 	/// @see <a href="http://www.opengl.org/registry/doc/GLSLangSpec.4.20.8.pdf">GLSL 4.20.8 specification, section 8.3 Common Functions</a>
 	template<length_t L, typename T, qualifier Q>
-	GLM_FUNC_DECL vec<L, T, Q> sign(vec<L, T, Q> const& x);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<L, T, Q> sign(vec<L, T, Q> const& x);
 
 	/// Returns a value equal to the nearest integer that is less then or equal to x.
 	///
@@ -306,13 +306,13 @@ namespace glm
 	/// glm::vec4 u = glm::mix(g, h, r); // Interpolations can be perform per component with a vector for the last parameter.
 	/// @endcode
 	template<typename genTypeT, typename genTypeU>
-	GLM_FUNC_DECL genTypeT mix(genTypeT x, genTypeT y, genTypeU a);
+	GLM_FUNC_DECL GLM_CONSTEXPR genTypeT mix(genTypeT x, genTypeT y, genTypeU a);
 
 	template<length_t L, typename T, typename U, qualifier Q>
-	GLM_FUNC_DECL vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, U, Q> const& a);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, U, Q> const& a);
 
 	template<length_t L, typename T, typename U, qualifier Q>
-	GLM_FUNC_DECL vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, U a);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, U a);
 
 	/// Returns 0.0 if x < edge, otherwise it returns 1.0 for each component of a genType.
 	///

glm/detail/func_common.inl

@@ -80,7 +80,7 @@ namespace detail
 	template<length_t L, typename T, typename U, qualifier Q, bool Aligned>
 	struct compute_mix_vector
 	{
-		GLM_FUNC_QUALIFIER static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, U, Q> const& a)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, U, Q> const& a)
 		{
 			GLM_STATIC_ASSERT(std::numeric_limits<U>::is_iec559 || GLM_CONFIG_UNRESTRICTED_GENTYPE, "'mix' only accept floating-point inputs for the interpolator a");
 
@@ -91,7 +91,7 @@ namespace detail
 	template<length_t L, typename T, qualifier Q, bool Aligned>
 	struct compute_mix_vector<L, T, bool, Q, Aligned>
 	{
-		GLM_FUNC_QUALIFIER static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, bool, Q> const& a)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, bool, Q> const& a)
 		{
 			vec<L, T, Q> Result;
 			for(length_t i = 0; i < x.length(); ++i)
@@ -103,7 +103,7 @@ namespace detail
 	template<length_t L, typename T, typename U, qualifier Q, bool Aligned>
 	struct compute_mix_scalar
 	{
-		GLM_FUNC_QUALIFIER static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, U const& a)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, U const& a)
 		{
 			GLM_STATIC_ASSERT(std::numeric_limits<U>::is_iec559 || GLM_CONFIG_UNRESTRICTED_GENTYPE, "'mix' only accept floating-point inputs for the interpolator a");
 
@@ -114,7 +114,7 @@ namespace detail
 	template<length_t L, typename T, qualifier Q, bool Aligned>
 	struct compute_mix_scalar<L, T, bool, Q, Aligned>
 	{
-		GLM_FUNC_QUALIFIER static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, bool const& a)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static vec<L, T, Q> call(vec<L, T, Q> const& x, vec<L, T, Q> const& y, bool const& a)
 		{
 			return a ? y : x;
 		}
@@ -123,7 +123,7 @@ namespace detail
 	template<typename T, typename U>
 	struct compute_mix
 	{
-		GLM_FUNC_QUALIFIER static T call(T const& x, T const& y, U const& a)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static T call(T const& x, T const& y, U const& a)
 		{
 			GLM_STATIC_ASSERT(std::numeric_limits<U>::is_iec559 || GLM_CONFIG_UNRESTRICTED_GENTYPE, "'mix' only accept floating-point inputs for the interpolator a");
 
@@ -134,7 +134,7 @@ namespace detail
 	template<typename T>
 	struct compute_mix<T, bool>
 	{
-		GLM_FUNC_QUALIFIER static T call(T const& x, T const& y, bool const& a)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static T call(T const& x, T const& y, bool const& a)
 		{
 			return a ? y : x;
 		}
@@ -143,7 +143,7 @@ namespace detail
 	template<length_t L, typename T, qualifier Q, bool isFloat, bool Aligned>
 	struct compute_sign
 	{
-		GLM_FUNC_QUALIFIER static vec<L, T, Q> call(vec<L, T, Q> const& x)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static vec<L, T, Q> call(vec<L, T, Q> const& x)
 		{
 			return vec<L, T, Q>(glm::lessThan(vec<L, T, Q>(0), x)) - vec<L, T, Q>(glm::lessThan(x, vec<L, T, Q>(0)));
 		}
@@ -153,7 +153,7 @@ namespace detail
 	template<length_t L, typename T, qualifier Q, bool Aligned>
 	struct compute_sign<L, T, Q, false, Aligned>
 	{
-		GLM_FUNC_QUALIFIER static vec<L, T, Q> call(vec<L, T, Q> const& x)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static vec<L, T, Q> call(vec<L, T, Q> const& x)
 		{
 			T const Shift(static_cast<T>(sizeof(T) * 8 - 1));
 			vec<L, T, Q> const y(vec<L, typename detail::make_unsigned<T>::type, Q>(-x) >> typename detail::make_unsigned<T>::type(Shift));
@@ -281,7 +281,7 @@ namespace detail
 	// sign
 	// fast and works for any type
 	template<typename genFIType>
-	GLM_FUNC_QUALIFIER genFIType sign(genFIType x)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR genFIType sign(genFIType x)
 	{
 		GLM_STATIC_ASSERT(
 			std::numeric_limits<genFIType>::is_iec559 || (std::numeric_limits<genFIType>::is_signed && std::numeric_limits<genFIType>::is_integer),
@@ -292,7 +292,7 @@ namespace detail
 	}
 
 	template<length_t L, typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<L, T, Q> sign(vec<L, T, Q> const& x)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<L, T, Q> sign(vec<L, T, Q> const& x)
 	{
 		GLM_STATIC_ASSERT(
 			std::numeric_limits<T>::is_iec559 || (std::numeric_limits<T>::is_signed && std::numeric_limits<T>::is_integer),
@@ -523,19 +523,19 @@ namespace detail
 	}
 
 	template<typename genTypeT, typename genTypeU>
-	GLM_FUNC_QUALIFIER genTypeT mix(genTypeT x, genTypeT y, genTypeU a)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR genTypeT mix(genTypeT x, genTypeT y, genTypeU a)
 	{
 		return detail::compute_mix<genTypeT, genTypeU>::call(x, y, a);
 	}
 
 	template<length_t L, typename T, typename U, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, U a)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, U a)
 	{
 		return detail::compute_mix_scalar<L, T, U, Q, detail::is_aligned<Q>::value>::call(x, y, a);
 	}
 
 	template<length_t L, typename T, typename U, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, U, Q> const& a)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<L, T, Q> mix(vec<L, T, Q> const& x, vec<L, T, Q> const& y, vec<L, U, Q> const& a)
 	{
 		return detail::compute_mix_vector<L, T, U, Q, detail::is_aligned<Q>::value>::call(x, y, a);
 	}

glm/ext/matrix_transform.hpp

@@ -61,7 +61,7 @@ namespace glm
 	/// @see - translate(vec<3, T, Q> const& v)
 	/// @see <a href="https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/glTranslate.xml">glTranslate man page</a>
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL mat<4, 4, T, Q> translate(
+	GLM_FUNC_DECL GLM_CONSTEXPR mat<4, 4, T, Q> translate(
 		mat<4, 4, T, Q> const& m, vec<3, T, Q> const& v);
 
 	/// Builds a rotation 4 * 4 matrix created from an axis vector and an angle.

glm/ext/matrix_transform.inl

@@ -7,7 +7,7 @@ namespace glm
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER mat<4, 4, T, Q> translate(mat<4, 4, T, Q> const& m, vec<3, T, Q> const& v)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR mat<4, 4, T, Q> translate(mat<4, 4, T, Q> const& m, vec<3, T, Q> const& v)
 	{
 		mat<4, 4, T, Q> Result(m);
 		Result[3] = m[0] * v[0] + m[1] * v[1] + m[2] * v[2] + m[3];

glm/ext/quaternion_common.hpp

@@ -62,7 +62,7 @@ namespace glm
 	/// @tparam T A floating-point scalar type
 	/// @tparam Q A value from qualifier enum
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL qua<T, Q> lerp(qua<T, Q> const& x, qua<T, Q> const& y, T a);
+	GLM_FUNC_DECL GLM_CONSTEXPR qua<T, Q> lerp(qua<T, Q> const& x, qua<T, Q> const& y, T a);
 
 	/// Spherical linear interpolation of two quaternions.
 	/// The interpolation always take the short path and the rotation is performed at constant speed.
@@ -96,14 +96,14 @@ namespace glm
 	/// @tparam T A floating-point scalar type
 	/// @tparam Q A value from qualifier enum
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL qua<T, Q> conjugate(qua<T, Q> const& q);
+	GLM_FUNC_DECL GLM_CONSTEXPR qua<T, Q> conjugate(qua<T, Q> const& q);
 
 	/// Returns the q inverse.
 	///
 	/// @tparam T A floating-point scalar type
 	/// @tparam Q A value from qualifier enum
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL qua<T, Q> inverse(qua<T, Q> const& q);
+	GLM_FUNC_DECL GLM_CONSTEXPR qua<T, Q> inverse(qua<T, Q> const& q);
 
 	/// Returns true if x holds a NaN (not a number)
 	/// representation in the underlying implementation's set of

glm/ext/quaternion_common.inl

@@ -26,7 +26,7 @@ namespace glm
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER qua<T, Q> lerp(qua<T, Q> const& x, qua<T, Q> const& y, T a)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR qua<T, Q> lerp(qua<T, Q> const& x, qua<T, Q> const& y, T a)
 	{
 		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'lerp' only accept floating-point inputs");
 
@@ -110,13 +110,13 @@ namespace glm
     }
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER qua<T, Q> conjugate(qua<T, Q> const& q)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR qua<T, Q> conjugate(qua<T, Q> const& q)
 	{
 		return qua<T, Q>::wxyz(q.w, -q.x, -q.y, -q.z);
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER qua<T, Q> inverse(qua<T, Q> const& q)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR qua<T, Q> inverse(qua<T, Q> const& q)
 	{
 		return conjugate(q) / dot(q, q);
 	}

glm/ext/quaternion_geometric.hpp

@@ -53,7 +53,7 @@ namespace glm
 	///
 	/// @see ext_quaternion_geometric
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL T dot(qua<T, Q> const& x, qua<T, Q> const& y);
+	GLM_FUNC_DECL GLM_CONSTEXPR T dot(qua<T, Q> const& x, qua<T, Q> const& y);
 
 	/// Compute a cross product.
 	///
@@ -62,7 +62,7 @@ namespace glm
 	///
 	/// @see ext_quaternion_geometric
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER qua<T, Q> cross(qua<T, Q> const& q1, qua<T, Q> const& q2);
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR qua<T, Q> cross(qua<T, Q> const& q1, qua<T, Q> const& q2);
 
 	/// @}
 } //namespace glm

glm/ext/quaternion_geometric.inl

@@ -1,7 +1,7 @@
 namespace glm
 {
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER T dot(qua<T, Q> const& x, qua<T, Q> const& y)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T dot(qua<T, Q> const& x, qua<T, Q> const& y)
 	{
 		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'dot' accepts only floating-point inputs");
 		return detail::compute_dot<qua<T, Q>, T, detail::is_aligned<Q>::value>::call(x, y);
@@ -24,7 +24,7 @@ namespace glm
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER qua<T, Q> cross(qua<T, Q> const& q1, qua<T, Q> const& q2)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR qua<T, Q> cross(qua<T, Q> const& q1, qua<T, Q> const& q2)
 	{
 		return qua<T, Q>::wxyz(
 			q1.w * q2.w - q1.x * q2.x - q1.y * q2.y - q1.z * q2.z,

glm/gtc/quaternion.hpp

@@ -112,7 +112,7 @@ namespace glm
 	///
 	/// @see ext_quaternion_relational
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL vec<4, bool, Q> lessThan(qua<T, Q> const& x, qua<T, Q> const& y);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<4, bool, Q> lessThan(qua<T, Q> const& x, qua<T, Q> const& y);
 
 	/// Returns the component-wise comparison of result x <= y.
 	///
@@ -121,7 +121,7 @@ namespace glm
 	///
 	/// @see ext_quaternion_relational
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL vec<4, bool, Q> lessThanEqual(qua<T, Q> const& x, qua<T, Q> const& y);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<4, bool, Q> lessThanEqual(qua<T, Q> const& x, qua<T, Q> const& y);
 
 	/// Returns the component-wise comparison of result x > y.
 	///
@@ -130,7 +130,7 @@ namespace glm
 	///
 	/// @see ext_quaternion_relational
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL vec<4, bool, Q> greaterThan(qua<T, Q> const& x, qua<T, Q> const& y);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<4, bool, Q> greaterThan(qua<T, Q> const& x, qua<T, Q> const& y);
 
 	/// Returns the component-wise comparison of result x >= y.
 	///
@@ -139,7 +139,7 @@ namespace glm
 	///
 	/// @see ext_quaternion_relational
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL vec<4, bool, Q> greaterThanEqual(qua<T, Q> const& x, qua<T, Q> const& y);
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<4, bool, Q> greaterThanEqual(qua<T, Q> const& x, qua<T, Q> const& y);
 
 	/// Build a look at quaternion based on the default handedness.
 	///

glm/gtc/quaternion.inl

@@ -129,36 +129,36 @@ namespace glm
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<4, bool, Q> lessThan(qua<T, Q> const& x, qua<T, Q> const& y)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<4, bool, Q> lessThan(qua<T, Q> const& x, qua<T, Q> const& y)
 	{
-		vec<4, bool, Q> Result;
+		vec<4, bool, Q> Result(false, false, false, false);
 		for(length_t i = 0; i < x.length(); ++i)
 			Result[i] = x[i] < y[i];
 		return Result;
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<4, bool, Q> lessThanEqual(qua<T, Q> const& x, qua<T, Q> const& y)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<4, bool, Q> lessThanEqual(qua<T, Q> const& x, qua<T, Q> const& y)
 	{
-		vec<4, bool, Q> Result;
+		vec<4, bool, Q> Result(false, false, false, false);
 		for(length_t i = 0; i < x.length(); ++i)
 			Result[i] = x[i] <= y[i];
 		return Result;
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<4, bool, Q> greaterThan(qua<T, Q> const& x, qua<T, Q> const& y)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<4, bool, Q> greaterThan(qua<T, Q> const& x, qua<T, Q> const& y)
 	{
-		vec<4, bool, Q> Result;
+		vec<4, bool, Q> Result(false, false, false, false);
 		for(length_t i = 0; i < x.length(); ++i)
 			Result[i] = x[i] > y[i];
 		return Result;
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<4, bool, Q> greaterThanEqual(qua<T, Q> const& x, qua<T, Q> const& y)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<4, bool, Q> greaterThanEqual(qua<T, Q> const& x, qua<T, Q> const& y)
 	{
-		vec<4, bool, Q> Result;
+		vec<4, bool, Q> Result(false, false, false, false);
 		for(length_t i = 0; i < x.length(); ++i)
 			Result[i] = x[i] >= y[i];
 		return Result;

glm/gtx/exterior_product.hpp

@@ -37,7 +37,7 @@ namespace glm
 	///
 	/// @see <a href="https://en.wikipedia.org/wiki/Exterior_algebra#Cross_and_triple_products">Exterior product</a>
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL T cross(vec<2, T, Q> const& v, vec<2, T, Q> const& u);
+	GLM_FUNC_DECL GLM_CONSTEXPR T cross(vec<2, T, Q> const& v, vec<2, T, Q> const& u);
 
 	/// @}
 } //namespace glm

glm/gtx/exterior_product.inl

@@ -8,7 +8,7 @@ namespace detail
 	template<typename T, qualifier Q, bool Aligned>
 	struct compute_cross_vec2
 	{
-		GLM_FUNC_QUALIFIER static T call(vec<2, T, Q> const& v, vec<2, T, Q> const& u)
+		GLM_FUNC_QUALIFIER GLM_CONSTEXPR static T call(vec<2, T, Q> const& v, vec<2, T, Q> const& u)
 		{
 			GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'cross' accepts only floating-point inputs");
 
@@ -18,7 +18,7 @@ namespace detail
 }//namespace detail
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER T cross(vec<2, T, Q> const& x, vec<2, T, Q> const& y)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR T cross(vec<2, T, Q> const& x, vec<2, T, Q> const& y)
 	{
 		return detail::compute_cross_vec2<T, Q, detail::is_aligned<Q>::value>::call(x, y);
 	}

glm/gtx/quaternion.hpp

@@ -43,7 +43,7 @@ namespace glm
 	///
 	/// @see gtx_quaternion
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL vec<3, T, Q> cross(
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<3, T, Q> cross(
 		qua<T, Q> const& q,
 		vec<3, T, Q> const& v);
 
@@ -51,7 +51,7 @@ namespace glm
 	///
 	/// @see gtx_quaternion
 	template<typename T, qualifier Q>
-	GLM_FUNC_DECL vec<3, T, Q> cross(
+	GLM_FUNC_DECL GLM_CONSTEXPR vec<3, T, Q> cross(
 		vec<3, T, Q> const& v,
 		qua<T, Q> const& q);
 

glm/gtx/quaternion.inl

@@ -12,13 +12,13 @@ namespace glm
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<3, T, Q> cross(vec<3, T, Q> const& v, qua<T, Q> const& q)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<3, T, Q> cross(vec<3, T, Q> const& v, qua<T, Q> const& q)
 	{
 		return inverse(q) * v;
 	}
 
 	template<typename T, qualifier Q>
-	GLM_FUNC_QUALIFIER vec<3, T, Q> cross(qua<T, Q> const& q, vec<3, T, Q> const& v)
+	GLM_FUNC_QUALIFIER GLM_CONSTEXPR vec<3, T, Q> cross(qua<T, Q> const& q, vec<3, T, Q> const& v)
 	{
 		return q * v;
 	}