self-mutating issues at the moment of change permisions - c++

Question

I am creating a self-mutation under Windows, but when I try to change my permissions page boundaries, it works under Dev C++, but the same code doesn't work under Visual Studio 2017. Once I compile it works, but it always return me original function result 1, mutation 1 when it should be 42.
Dev C++
int change_page_permissions_of_address(void *addr) {
// Move the pointer to the page boundary
int page_size = getpagesize();
DWORD dwOldProtect;
addr -= (unsigned uintptr_t)addr % page_size; // it works under dev c++
if(VirtualProtect(addr, page_size, PAGE_EXECUTE_READWRITE,&dwOldProtect) == -1) {
return -1;
}
return 0;
}
Visual Studio 2017
int change_page_permissions_of_address(void* address) {
// Move the pointer to the page boundary
unsigned char* addr = reinterpret_cast<unsigned char *>(address); // cast before operation
int page_size = getpagesize();
DWORD dwOldProtect;
addr -= (uintptr_t)addr % page_size; // doesnt work under visual studio
if (VirtualProtect(addr, page_size, PAGE_EXECUTE_READWRITE, &dwOldProtect) == -1) {
return -1;
}
return 0;
}
main
int main(){
void *foo_addr = (void*)foo;
if(change_page_permissions_of_address(foo_addr) == -1) {
fprintf(stderr, "Error while changing page permissions of foo(): %s\n", strerror(errno));
return 1;
}
// Call the unmodified foo()
puts("Calling foo...");
foo();
// Change the immediate value in the addl instruction in foo() to 42
unsigned char *instruction = (unsigned char*)foo_addr + 18;
*instruction = 0x2A;
// Call the modified foo()
puts("Calling foo..., but I am the self-modifying");
foo();
return 0;
}
self-mutation_visual