UV Mapping issue artifact on Sphere OpenGl - c++

Question

I am UV mapping a 2D Texture on a 3d sphere X, Y, Z coordinates, by using the formula
u = (0.5 + atan2(X, Y) / (2 * glm::pi<double>()));
v = (0.5 - asin(Z) / glm::pi<double>());
in modern openGL C++.
I dont know why there is this artifact in the sphere. Cant figure it out.

Answer 1

Ok, I have figured and corrected this out, thought I will answer here finally now.
Big thanks to BDL and Rabbid76.
Whenever u == 0, I added the same vertex position (X Y Z) to the vertices vector (or array) and also increased the index, but hardcoding the texture u to be 1.0f this time.
No issues now, the seam looks perfect now.

Answer 2

This is detail of a textured sphere geometry which is indexed. You should use index for better performance:
m_meridians and m_latitudes are detail level of sphere.
for (size_t i = 0; i < m_meridians + 1; i++)
{
for (size_t j = 0; j < m_latitudes + 2; j++)
{
// texCoord in the range [(0,0), (1,1)]
QVector2D texCoord((float)i / m_meridians, (float)j / (m_latitudes+1));
// theta = longitude from 0 to 2pi
// phi = latitude from -pi/2 to pi/2
double theta, phi;
theta = 2*M_PI * texCoord.x();
phi = M_PI * texCoord.y() - M_PI_2;
QVector3D pos;
pos.setY((float)std::sin(phi));
pos.setX((float)std::cos(phi) * std::cos(theta));
pos.setZ((float)std::cos(phi) * std::sin(theta));
m_vertices.push_back({pos, texCoord});
}
}
// Calculate triangle indices
for (size_t i = 0; i < m_meridians; i++)
{
// Construct triangles between successive meridians
for (size_t j = 0; j < m_latitudes + 1; j++)
{
m_indices.push_back(i * (m_latitudes+2) + j);
m_indices.push_back(i * (m_latitudes+2) + j+1);
m_indices.push_back((i+1) * (m_latitudes+2) + j+1);
m_triangleCount++;
m_indices.push_back((i+1) * (m_latitudes+2) + j+1);
m_indices.push_back((i+1) * (m_latitudes+2) + j);
m_indices.push_back(i * (m_latitudes+2) + j);
m_triangleCount++;
}
}