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digitalmars.D.learn - Safe to throw away function arguments with cast?

reply Brian <digitalmars brianguertin.com> writes:
Is it safe to cast a function(or delegate) into one that takes more 
arguments, causing those arguments to be ignored?
Example:

void fn() {
}

auto fptr = cast(void function(int, int))&fn;
fptr(1, 2);

// It seems to work with a simple test case, I'm just afraid of it 
blowing up at me later on.
Dec 04 2008
next sibling parent "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Thu, Dec 4, 2008 at 10:37 AM, Brian <digitalmars brianguertin.com> wrote:

 Is it safe to cast a function(or delegate) into one that takes more
 arguments, causing those arguments to be ignored?
 Example:

 void fn() {
 }

 auto fptr = cast(void function(int, int))&fn;
 fptr(1, 2);

 // It seems to work with a simple test case, I'm just afraid of it
 blowing up at me later on.



No.  According to the D ABI, the callee cleans the stack.  So if you
pass more parameters than the function expects, you'll end up trashing
the stack by leaving extra values on it.
Dec 04 2008
prev sibling next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Thu, 04 Dec 2008 18:37:10 +0300, Brian <digitalmars brianguertin.com>  
wrote:


 Is it safe to cast a function(or delegate) into one that takes more
 arguments, causing those arguments to be ignored?
 Example:

 void fn() {
 }

 auto fptr = cast(void function(int, int))&fn;
 fptr(1, 2);

 // It seems to work with a simple test case, I'm just afraid of it
 blowing up at me later on.



Try using type-safe alternatives:

auto fptr = (int,int) {
     fn();
}
Dec 04 2008
prev sibling parent "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Thu, Dec 4, 2008 at 12:23 PM, Denis Koroskin <2korden gmail.com> wrote:

 On Thu, 04 Dec 2008 18:37:10 +0300, Brian <digitalmars brianguertin.com>
 wrote:


 Is it safe to cast a function(or delegate) into one that takes more
 arguments, causing those arguments to be ignored?
 Example:

 void fn() {
 }

 auto fptr = cast(void function(int, int))&fn;
 fptr(1, 2);

 // It seems to work with a simple test case, I'm just afraid of it
 blowing up at me later on.



 Try using type-safe alternatives:

 auto fptr = (int,int) {
    fn();
 }



That's only safe in the context of the declaring function, in D1 at least.
Dec 04 2008