GL_LINE_STRIP always terminates at the origin - opengl

Question

I mean for the following code to draw a horizontal line across the screen. Instead, it draws the line and then draws a line that fades off towards the origin. A picture is posted below.
I think that the critical pieces of code are
float vertices[] =
{
-0.5, 0.7, 1, 1, 1,
0.5, 0.7, 1, 1, 1
};
and
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
while (not glfwWindowShouldClose(window))
{
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_LINE_STRIP, 0, sizeof(vertices)/sizeof(float));
glfwSwapBuffers(window);
glfwPollEvents();
}
The full code is
# include <GL/glew.h>
# include <GLFW/glfw3.h>
const GLchar * vertex_shader_source =
"\
# version 150 core\n\
in vec2 position;\
in vec3 color;\
out vec3 Color;\
void main() { Color = color; gl_Position = vec4(position, 0, 1); }\
";
const GLchar * fragment_shader_source =
"\
# version 150 core\n\
in vec3 Color;\
out vec4 outColor;\
void main() { outColor = vec4(Color, 1.0); }\
";
float vertices[] =
{
-0.5, 0.7, 1, 1, 1,
0.5, 0.7, 1, 1, 1
};
int main (int argc, char ** argv)
{
// ---- INITIALIZE STUFF ---- //
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
GLFWwindow * window = glfwCreateWindow(800, 600, "open-gl", nullptr, nullptr);
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE;
glewInit();
// ---- MAKE SHADERS ---- //
GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
glCompileShader(vertex_shader);
GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
glCompileShader(fragment_shader);
GLuint shader_program = glCreateProgram();
glAttachShader(shader_program, vertex_shader);
glAttachShader(shader_program, fragment_shader);
glBindFragDataLocation(shader_program, 0, "outColor");
glLinkProgram(shader_program);
glUseProgram(shader_program);
// ---- MAKE VERTEX BUFFER OBJECT ---- //
GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
// ---- MAKE VERTEX ARRAY OBJECT ---- //
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
GLint posAttrib = glGetAttribLocation(shader_program, "position");
GLint colAttrib = glGetAttribLocation(shader_program, "color");
glEnableVertexAttribArray(posAttrib);
glEnableVertexAttribArray(colAttrib);
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 5*sizeof(float), 0);
glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, 5*sizeof(float), (void*)(2*sizeof(float)));
// ---- DO OTHER THINGS ---- //
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
while (not glfwWindowShouldClose(window))
{
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_LINE_STRIP, 0, sizeof(vertices)/sizeof(float));
glfwSwapBuffers(window);
glfwPollEvents();
}
// ---- CLEAN UP ---- //
glDeleteProgram(shader_program);
glDeleteShader(vertex_shader);
glDeleteShader(fragment_shader);
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &vbo);
glfwTerminate();
return 0;
}
The output is
I have no idea what the problem is; I have searched the internet, but I cannot find anyone who has had a similar problem. The best that I have found is someone who said that OpenGL implementations do not tend to do lines very well. This does not happen with GL_LINES, however.
I am using OpenGL 3.2 with GLFW and GLEW. I have an Acer Aspire v5-571P-6648; I do not know specifically what model of graphics card it has, but I can look for it.

Answer 1

You last argument for
glDrawArrays(GL_LINE_STRIP, 0, sizeof(vertices)/sizeof(float));
is wrong, it should be 2 (see https://www.opengl.org/sdk/docs/man/html/glDrawArrays.xhtml).