多个char指针（glShaderSource）时发生GLSL编译错误

Question

What's wrong with this code for a 3.30 OpenGL and GLSL version?

    const char *vertSrcs[2] = { "#define A_MACRO\n", vShaderSrc };
    const char *fragSrcs[2] = { "#define A_MACRO\n", fShaderSrc };
    glShaderSource(vId, 2, vertSrcs, NULL);
    glShaderSource(fId, 2, fragSrcs, NULL);

I gather the shader state with GL_COMPILE_STATUS after the its compiled, get this error:

    Vertex shader failed to compile with the following errors:

The purpose for this macro is to change type qualifier on a color I passed from the vertex to the fragment, maybe there is another way to do that using a uniform and the layout but the question is why would the shader fail? I wonder if there is another OpenGL command which must specify the 2 char pointers. By the way, this works:

 ...
 glShaderSource(vId, 1, &vertSrcs[1], NULL);
 ...

EDIT : since I can't answer my own questions, found the solution

Very strange problem, the string loader happens to be the problem. Without using ifstream along with std::ios::in | std::ios::binary flags, the string was loaded with some garbage information to the end even with null terminated, therefore concatenating the strings will produce the error. For some reason the gl compiler didn't complain before with the single string version, besides calling

inStream.flags(std::ios::in | std::ios::binary)

wasn't enough, it need to be specified when opening, didn't find any doc for this.

Answer 1

The very first nonempty line of a GLSL shader must be a #version preprocessor statement. Anything else is an error.