C++ error C4700: uninitialized local variable 'i' used - c++

Question

1>------ Build started: Project: RageBotGamingEngine, Configuration: Debug Win32 ------
1> Sprite.cpp
1>c:\users\nha\documents\visual studio 2013\projects\ragebotgamingengine\ragebotgamingengine\sprite.cpp(51): error C4700: uninitialized local variable 'i' used
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
Above is what the output logs say.
Below are some related files that could be involved with this problem:
Sprite.cpp
#include "Sprite.h"
#include "Vertex.h"
#include <cstddef>
Sprite::Sprite()
{
_vboID = 0;
}
Sprite::~Sprite()
{
if (_vboID != 0) {
glDeleteBuffers(1, &_vboID);
}
}
void Sprite::init(float x, float y, float width, float height) {
_x = x;
_y = y;
_width = width;
_height = height;
if (_vboID == 0) {
glGenBuffers(1, &_vboID);
}
Vertex vertexData[6];
//First Triangle
vertexData[0].position.x = x + width;
vertexData[0].position.y = y + width;
vertexData[1].position.x = x;
vertexData[1].position.y = y + height;
vertexData[2].position.x = x;
vertexData[2].position.y = y;
//Second Triangle
vertexData[3].position.x = x;
vertexData[3].position.y = y;
vertexData[4].position.x = x + width;
vertexData[4].position.y = y;
vertexData[5].position.x = x + width;
vertexData[5].position.y = y + height;
for (int i; i < 6; i++) {
vertexData[i].color.r = 255;
vertexData[i].color.g = 0;
vertexData[i].color.b = 255;
vertexData[i].color.a = 255;
}
glBindBuffer(GL_ARRAY_BUFFER, _vboID);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
void Sprite::draw() {
glBindBuffer(GL_ARRAY_BUFFER, _vboID);
glEnableVertexAttribArray(0);
//This is position attribute pointer
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, position));
//This is color attribute pointer
glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(Vertex), (void*)offsetof(Vertex, color));
glDrawArrays(GL_TRIANGLES, 0, 6);
glDisableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
I have tried to find the problem but I'm relatively new to OpenGL, SDL, & C++ & as you can imagine it has been a huge hassle because of the fact that the OpenGL wiki isn't exactly easy to follow & consistent. Just about any help would be very much needed as well as appreciated.
I'm trying to create a Game Engine (obviously I'm pretty much un-skilled & lack the time to develop this project)

Answer 1

for (int i; i < 6; i++)
should be
for (int i=0; i < 6; i++)
You declared variable 'i' but forgot to initialise the variable, so it could have any arbitrary value, not necessarily '0'