Any error in second cpp file not recognised - c++

Question

I have 1 header file and 2 .cpp files (I've included main.cpp) and work on CodeBlocks. My problem is that compiler not see the errors in the second .cpp file (graph_interface.cpp) when I build it. Do you have any suggestions? Where am I going wrong?.
Simply I get the output even I did the wrong thing in graph_implementation.cpp file:
Target is up to date.
Nothing to be done (all items are up-to-date).
For example, my code in main.cpp
//main.cpp
#include "graph_interface.h"
int main(int argc,char *argv[])
{
return 0;
}
graph_interface.h file
#ifndef GRAPH_INTERFACE_H_INCLUDED
#define GRAPH_INTERFACE_H_INCLUDED
typedef struct{int v;int w;} Edge;
Edge EDGE(int,int);
typedef struct graph *Graph;
Graph GRAPHinit(int);
void GRAPHinsertE(Graph,Edge);
void GRAPHremoveE(Graph,Edge);
int GRAPHedges(Edge[],Graph G);
Graph GRAPHcopy(Graph);
void GRAPHdestroy(Graph);
#endif // GRAPH_INTERFACE_H_INCLUDED
And other cpp file graph_implementation.cpp
#include "graph_interface.h"
using namespace std;
struct graph{
int V;
int E;
int **adj;
};
Graph GRAPHinit(int V){
Graph G=malloc(sizeof *G);
G->V=V;
G->E=0;
G->adj=MATRIXint(V,V,0);
return G;
;// not give anything
}

Answer 1

If you're expecting the line:
;// not give anything
to produce an error, the reason you aren't seeing one is because empty statements are perfectly legal in C++; This line does not contain any error.
// complete, legal C++ program
int main() {
;
}
Using new/delete or malloc/free this way goes against modern C++ practice because it's very difficult to do correctly. Modern practice would be more like:
class Graph {
int V;
Matrix adj;
public:
Graph(int V)
: V(V), adj(V*V, 0)
{}
}
int main() {
Graph g; // automatically initialized and destroyed correctly
// ...
}