CODEWITHSUNDEEP
c++openglglsl
Berry
Berry

Reputation: 23

Why do I get a linking error when there should be nothing wrong

I'm a Java developer and I recently switched to C++. I've been trying to make a little OpenGL program and I ran into a problem. Whenever I try compiling my shader program it gives a linking error. Here it is:

ERROR::SHADER::PROGRAML::LINKING_ERROR
Link info
---------
error: "TexCoord" not declared as an output from the previous stage

Here are the shader files:

Vertex:

#version 440 core

layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;

out vec3 ourColor;
out vec2 TexCoord;

void main()
{
    gl_Position = vec4(aPos, 1.0);
    ourColor = aColor;
    TexCoord = vec2(aTexCoord.x, aTexCoord.y);
}

Fragment

#version 440 core

out vec4 FragColor;

in vec3 ourColor;
in vec2 TexCoord;

// texture sampler
uniform sampler2D texture1;

void main()
{
    FragColor = texture(texture1, TexCoord);
}

And here is the shader creation:

int success;
char infoLog[512];

const char* vertexSource;
const char* fragmentSource;

// Load in shader source

std::ifstream inFile;

inFile.open(vertexPath);

std::string temp = "";
std::string source = "";

if (inFile.is_open())
{
    while (std::getline(inFile, temp))
        source += temp + "\n";
}
else
{
    std::cout << "ERROR::SHADER::VERTEX::COULD_NOT_OPEN_SOURCE_FILE" << std::endl;
}

inFile.close();

vertexSource = source.c_str();

temp = "";
source = "";

inFile.open(fragmentPath);

if (inFile.is_open())
{
    while (std::getline(inFile, temp))
        source += temp + "\n";
}
else
{
    std::cout << "ERROR::SHADER::FRAGMENT::COULD_NOT_OPEN_SOURCE_FILE" << std::endl;
}

inFile.close();

fragmentSource = source.c_str();

unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexSource, nullptr);
glCompileShader(vertexShader);

glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
    glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
    std::cout << "ERROR::SHADER::VERTEX::COULD_NOT_COMPILE\n" << infoLog << std::endl;
}

unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentSource, nullptr);
glCompileShader(fragmentShader);

glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
    glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
    std::cout << "ERROR::SHADER::FRAGMENT::COULD_NOT_COMPILE\n" << infoLog << std::endl;
}

// Program

ID = glCreateProgram();
glAttachShader(ID, vertexShader);
glAttachShader(ID, fragmentShader);
glLinkProgram(ID);

glGetProgramiv(ID, GL_LINK_STATUS, &success);
if (!success)
{
    glGetProgramInfoLog(ID, 512, nullptr, infoLog);
    std::cout << "ERROR::SHADER::PROGRAML::LINKING_ERROR\n" << infoLog << std::endl;
}

glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
glUseProgram(0);

To my understanding, I should only be getting this error if the two variables that I'm trying to link aren't the same name or type, but they are. I just don't understand.

Thanks.

Upvotes: 0

Views: 108

Answers (1)

G.M.
G.M.

Reputation: 12879

You essentially have...

std::string source;
const char *vertexSource;
const char *fragmentSource;

...read into source...

vertexSource = source.c_str();

...read into source...

fragmentSource = source.c_str();

The pointer stored in vertexSource will be invalidated by the second read into source. From the documentation

The pointer obtained from c_str() may be invalidated by:

  • Passing a non-const reference to the string to any standard library function, or
  • Calling non-const member functions on the string, excluding operator[], at(), front(), back(), begin(), rbegin(), end() and rend().

Upvotes: 2

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