There is consensus that the way delegates are currently implemented (effectively untyped void pointer + incorrectly typed function pointer without this parameter) should be revised.
In addition to function pointer problem which is raised in issue 2672 there is also problem with context pointer, but which is expressed not only in the fact that it is void*, but in the fact that it is mutable.
extern(C) @system int printf(const char*, ...);
auto frame1() pure nothrow @safe
{
immutable void delegate() pure nothrow @safe x;
auto tmp = { return x; } ;
return tmp;
}
auto frame2(T)(T t) pure nothrow @safe
{
void delegate() @system x;
x.funcptr = t;
return { return x; } ;
}
void bar() { printf("pure nothrow @safe loophole\n"); } @system
void main() @safe pure nothrow
{
//bar(); Error: ...
auto fm1 = frame1();
auto fm2 = frame2(&bar);
fm1.ptr = fm2.ptr; // from type system point of view it is void*=void*
// but actually void pure nothrow @safe = @system
fm1()();
}
This prints "pure nothrow @safe loophole". It is hole not only with respect to these attributes, but also can be used to reinterpret at runtime different types.
Comment #1 by moonlightsentinel — 2021-11-05T00:18:47Z
*** This issue has been marked as a duplicate of issue 1983 ***