Effectivement, pas de warning, mais:

thunder:~ Fabien$ cat test.cpp && g++ -Wall test.cpp -o test && ./test
#include <iostream>

const int val = 1;

using namespace std;

int main(int argc, char *argv[])
{
	const int *pValOk = &val;
	int *pValNok = (int*)&val;

	*pValNok = 2;
	cout << "Val: " << val << endl << "Val 1: " << *pValOk << endl << "Val 2: " << *pValNok << endl;

	return 0;
}

Bus error

(Mac OS X 10.5.8)
EDIT: ./12 > Ouais c'est ce que je voulais dire par "signification trop importante"