How to pass an std::string to glShaderSource?

Question

I have the following code:

glShaderSource(shader, 1, (const char **)data.c_str(), NULL);

But it makes my program crash. How do I convert

Answer 1

glShaderSource signature is, according to glShaderSource doc:

void glShaderSource(
    GLuint shader,
    GLsizei count,
    const GLchar** string,
    const GLint* length);

where string "Specifies an array of pointers to strings containing the source code to be loaded into the shader". What you're trying to pass is a pointer to a NULL terminated string (that is, a pointer to a const char*).

Unfortunately, I am not familiar with glShaderSource, but I can guess it's not expected a pointer to "some code" but something like this instead:

const char** options =
{
    "option1",
    "option2"
    // and so on
};

From opengl-redbook, you can read an example (I've shortened it in purpose):

const GLchar* shaderSrc[] = {
    "void main()",
    "{",
    "    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;",
    "}"
};
shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(shader, NumberOfLines(shaderSrc), shaderSrc, NULL);