Stack corruption due to different pointer types

The C programming language allows you to send a float pointer to a function that expects a double pointer, which causes stack corruption. Example code:

	//Stack corruption due to different pointer types.
	//Note1: This code only builds in C. C++ compiler does not build it.
	//Note2: You will see the stack corruption message only when building in debug mode. In release mode, you won't see an error message.
	//Şamil Korkmaz, March 2020
	#include<stdio.h>
	void fun(double *val_d) { //double pointer
	*val_d = 5;
	}
	int main() {
	float val_f1 = 1;
	double val_d = 2;
	val_f1 = val_d; //Assigning a double to a float does not cause problems (as long as double value is small enough to fit into float)
	printf("val_f1: %1.3f\n", val_f1);
	float val_f2 = 10;
	fun(&val_f2); //Sending float pointer to a function that expects double pointer which causes stack corruption.
	printf("val_f2: %1.3f\n", val_f2);
	printf("Press enter...\n");
	getchar();
	}

view raw stackCorruption.c hosted with ❤ by GitHub

When you run it, you will see that the val_f2 is zero (should be 5):

Visual Studio 2015 will only display stack corruption message when you build in debug mode. In release mode, you don't get a message.

If you copy the same code to a cpp file, Visual Studio will use the C++ compiler and it will not build the code, saying that types are incompatible.