Problem trying to open a file with ifstream using CMake - c++

Question

/*
Defines the class Shader.
*/
I am developing an application in C++ with OpenGL and CMake. The structure of my directories is:
tanx
CMakeLists.txt
ext (contains GLFW and glad)
src
TanX.cpp
TanX.h
math (contains a couple of math methods; not very relevant for my problem)
Shader
Shader.h
vertex.glsl
fragment.glsl
CMakeLists.txt
Shader.h ist mainly supposed to read vertex and fragment shader sources from files, compile them and link them to a Shader program. It looks like this:
#ifndef _SHADER_H
#define _SHADER_H
#include <string>
#include <exception>
#include <fstream>
#include <glad.h>
class shader_exception :std::exception {
private:
const char* text;
public:
shader_exception(const char* text)
: text(text) {}
virtual const char* what() const {
return text;
}
};
class Shader {
private:
std::string* vertex_source = new std::string();
std::string* fragment_source = new std::string();
unsigned int vao, vbo, vertex_shader, fragment_shader, program;
public:
Shader(const char* vertex_source_path, const char* fragment_source_path) {
std::ifstream file_reader;
file_reader.open(vertex_source_path);
std::string line;
if (file_reader.is_open()) {
while (getline(file_reader, line)) {
vertex_source->append(line + "\n");
}
file_reader.close();
}
else
throw shader_exception("Could not open vertex shader source file");
file_reader.open(fragment_source_path); // this is where I get an unhandled exception dialog box
if (file_reader.is_open()) {
while (getline(file_reader, line)) {
fragment_source->append(line + "\n");
}
file_reader.close();
}
else
throw shader_exception("Could not open fragment shader file");
const char** vertex_source_c = (const char**)malloc(vertex_source->size());
*vertex_source_c = vertex_source->c_str();
const char** fragment_source_c = (const char**)malloc(fragment_source->size());
*fragment_source_c = fragment_source->c_str();
vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex_shader, 1, vertex_source_c, NULL);
glCompileShader(vertex_shader);
int success;
glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
char infoLog[512];
if (!success) {
glGetShaderInfoLog(vertex_shader, 512, NULL, infoLog);
throw shader_exception(infoLog);
}
glShaderSource(fragment_shader, 1, fragment_source_c, NULL);
glCompileShader(fragment_shader);
glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(fragment_shader, 512, NULL, infoLog);
throw shader_exception(infoLog);
}
program = glCreateProgram();
glAttachShader(program, vertex_shader);
glAttachShader(program, fragment_shader);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(program, 512, NULL, infoLog);
throw shader_exception(infoLog);
}
glDeleteShader(vertex_shader);
glDeleteShader(fragment_shader);
}
Shader() = delete;
void use()
{
glUseProgram(program);
}
~Shader() {
glDeleteProgram(program);
}
};
#endif
In TanX.cpp, I try to create a Shader object like this:
Shader shader("vertex.glsl", "fragment.glsl");
As you can see, the shader source files I'd like to use are vertex.glsl and fragment.glsl which are located in the "Shader" - folder. In order to make them usable to ifstream, the CMakeLists.txt file in the Shader-folder looks like this (This is one of the options mentioned here to make files usable for the program):
configure_file(${CMAKE_CURRENT_SOURCE_DIR}/vertex.glsl ${CMAKE_CURRENT_BINARY_DIR} COPYONLY)
configure_file(${CMAKE_CURRENT_SOURCE_DIR}/fragment.glsl ${CMAKE_CURRENT_BINARY_DIR} COPYONLY)
The top-level CMakeLists.txt file also contains
add_subdirectory("TanX/src/Shader")
so that the CMakeLists.txt file in Shader is executed.
The problem is that when I try to run my code in Visual Studio, I get an unhandled exception in the Shader.h file, at line 45 (where it tries to open fragment.glsl). It is a shader_exception, so apparently opening vertex.glsl failed. The details of the "Exception Unhandled" - Dialog Box: "Unhandled exception at 0x00007FFF43E4A388 in TanX.exe: Microsoft C++ exception: shader_exception at memory location 0x00000028896FF608. occurred". Now I have two questions
1) What do I neeed to do to get ifstream to open vertex.glsl (and then fragment.glsl after that)?
2) Why do I even get an unhandled exception error, shouldn't construction of the Shader-object fail as soon as the exception gets thrown and that lead to the program not even reach line 45?

Answer 1

Right off the bat, this ...
Shader* shader;
try {
*shader = Shader("vertex.glsl", "fragment.glsl");
}
... is undefined behavior, because you are dereferencing an uninitialized pointer (i.e., you haven't allocated any storage for the Shader object). This may not be the only problem but it is a critical one that must be fixed before you can debug further (because the behavior of the program afterward is unpredictable).
You probably meant to write:
shader = new Shader(...);
(And really you should use std::unique_ptr for this rather than a bare pointer, but this is veering out of the scope of the original question. Among other benefits, it makes this kind of error easier to spot and avoid.)
As for other problems, have you checked that the program is run in the directory where the .glsl files are located? Relative paths passed to file streams are interpreted relative to the program's current working directory, not relative to the location of the original source file.
By my count, line 45 is ...
}
... so something seems to be misaligned. It would be helpful to post the actual program output and exception information (or dialog box contents) along with line numbers or an annotation showing the line the debugger is indicating.

Answer 2

The problem was where I put the files to. I put them into the bin folder of the Shader folder, but as it is implemented in the header, the correct place is the bin folder of the top-level folder.