Changing default sizes of data types

[Anirudh]

Is there a way to get different return values for sizeof(int*) etc.
Right now, it is 4 on my machine...I want it to return, say, 3.
Basically, I'd like to play around with alignment issues that might
arise with memory allocation if sizeof(int) != sizeof(int*).

Thanks in advance
Anirudh

 

[Jens.Toerring]

Is there a way to get different return values for sizeof(int*) etc.
Right now, it is 4 on my machine...I want it to return, say, 3.

Write your own compiler;-)

Basically, I'd like to play around with alignment issues that might
arise with memory allocation if sizeof(int) != sizeof(int*).

There are easier way to do unaligned access than fiddling with the
compiler, e.g (untested and error checking omitted for obvious
reasons;-)

char *c = malloc( 2 * sizeof( int ) );
int i;

for ( i = 0; i < sizeof( int ); i++ )
{
* ( int * ) ( c + i ) = i;
print( "%d: %d\n", i, * ( int * ) ( c + i ) );
}

If this crashes with a bus error (or whatever it's called on your
system) you have a system that won't allow unaligned access. If it
does not crash te system the alternatives are either that unaligned
accesses are not flagged or that you have sizeof(int) == 1.

Regards, Jens

 

[Dan Pop]

Is there a way to get different return values for sizeof(int*) etc.
Right now, it is 4 on my machine...I want it to return, say, 3.

Do you realise ALL the implications of changing the size of a data type?
Basically, you have a new implementation, needing its own library and
so on.

Dan

 

[Malcolm]

Is there a way to get different return values for sizeof(int*) etc.
Right now, it is 4 on my machine...I want it to return, say, 3.
Basically, I'd like to play around with alignment issues that might
arise with memory allocation if sizeof(int) != sizeof(int*).

As others have siad, the only way to change the size of an int is to write
your own compiler.
However if the code is portable you should be able to compile it with a
different compiler and see if it still works. For example a lot of old DOS
compilers don't have sizeof(int) == sizeof(int *), so you should be able to
pick up code that makes this assumption.