Compilation issues in OpenGL code with g++ [duplicate]

Question

When I try compiling the opengl Code written in c language with gcc with the following commands it runs fine :

gcc -Wall tutorial10.c -lGL -lglut -lGLU

But when I try doing the same compiling it by using g++

g++ -Wall tutorial10.c -lGL -lglut -lGLU

It starts to give a lot of errors like this :

tutorial10.c: In function ‘void drawRect()’:
tutorial10.c:28:34: error: ‘glClearBufferfv’ was not declared in this scope
tutorial10.c:34:28: error: ‘glUseProgram’ was not declared in this scope
tutorial10.c:36:24: error: ‘glGenBuffers’ was not declared in this scope
tutorial10.c:37:37: error: ‘glBindBuffer’ was not declared in this scope
tutorial10.c:47:71: error: ‘glBufferData’ was not declared in this scope
tutorial10.c:49:52: error: ‘glVertexAttribPointer’ was not declared in this scope
tutorial10.c:50:29: error: ‘glEnableVertexAttribArray’ was not declared in this scope
tutorial10.c:52:60: error: ‘glGetUniformLocation’ was not declared in this scope
tutorial10.c:54:42: error: ‘glUniform4f’ was not declared in this scope
tutorial10.c:59:30: error: ‘glDisableVertexAttribArray’ was not declared in this scope
tutorial10.c: In function ‘int main(int, char**)’:
tutorial10.c:93:34: error: ‘glCreateProgram’ was not declared in this scope
tutorial10.c:95:54: error: ‘glCreateShader’ was not declared in this scope
tutorial10.c:124:76: error: ‘glShaderSource’ was not declared in this scope
tutorial10.c:128:36: error: ‘glCompileShader’ was not declared in this scope
tutorial10.c:134:49: error: ‘glAttachShader’ was not declared in this scope
tutorial10.c:136:29: error: ‘glLinkProgram’ was not declared in this scope
tutorial10.c:147:35: error: ‘glDeleteShader’ was not declared in this scope

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Headers from comment:

#include<stdio.h>
#include<stdlib.h>
#include<GL/glut.h>
#include<malloc.h>
#include<string.h>
#include<math.h>

Answer 1

You don't have opengl functions declarations within your translation unit (most likely, you haven't included <GL/gl.h>).

gcc takes that because older versions of C language allows implicit declarations - whenever you use function, gcc automatically declares it with generic rules. It does NOT mean functions will be called properly - implicit rules are very generic and will cause problems on e.g. float argument types, so expect a lot of bugs here.

You can see warnings about implicit declarations if you add -Wimplicit-function-declaration (or -Wall, which includes this, along with many others) to your cflags.

g++, on other side, enabled C++ mode, which forbids implicit declarations.

To sum it all, don't use implicit declarations unless you truly understand what they do (but in that case you wouldn't want to use them anyway).