glad.c unable to find glad/glad.h, but main.cpp can - c++

Question

I've been trying to set up a build environment for OpenGL using glfw3 and GLAD. I'm currently using WSL2 Ubuntu with an X Server for compilation and a makefile.
However, when I run my make I receive the following error:
src/glad.c:25:10: fatal error: glad/glad.h: No such file or directory
25 | #include <glad/glad.h>
This is odd to me because it seems that the makefile is able to compile the main.cpp file and create a main.o despite also including "glad/glad.h"
File structure:
-HelloTriangle
--include
---glad
----glad.h
---KHR
----khrplatform.h
--src
---glad.c
---main.cpp
--makefile
This is my make file:
BASE_OBJS = main.o glad.o
SRC_PATH = src
OBJS = $(addprefix $(SRC_PATH)/, $(BASE_OBJS))
CXX = g++
CXXFLAGS = -g -Iinclude
LDFLAGS =
LDLIBS = -lglfw -lGL -lX11 -lpthread -lXrandr -lXi -ldl
HelloTriangle: $(OBJS)
$(CXX) -o $# $(LDFLAGS) $^ $(LDLIBS)
clean:
rm $(OBJS)
This is my main.cpp:
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#define WINDOW_WIDTH 800
#define WINDOW_HEIGHT 600
/*
Function to handle window resizing
*/
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
int main() {
/*
Initialize GLFW
Sets version to Core profile 3.3
*/
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
/*
Initialize a window context for OpenGL
Defines the windows width, height, and title
*/
GLFWwindow* window = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, "Hello Triangle", NULL, NULL);
if(window == NULL) {
std::cout << "Failed to create GLFW window" <<std::endl;
glfwTerminate();
return -1;
}
/*
Initialize GLAD
Handles OS-specific function pointers
*/
if(!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
/*
Handle window resizing
*/
glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
/*
Render loop
*/
while(!glfwWindowShouldClose(window)) {
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height) { glViewport(0, 0, width, height); }

Answer 1

You seem to set the CXXFLAGS (for the C++ compiler), but your glad.c is compiled with the C-compiler (which checks CFLAGS)