gcc equivelant of +M2 +DD64 (LP64 issues)

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I am porting a HP10.20 app to HP11.00.  Is 
there a way
to have gcc generate warnings related to LP64 
issues.
e.g.
 
main()
{
long l1;
int i1;
 
i1 = l1;
}
 
Compiled with cc +M2 +DD64 file.c gives the 
following 
warning 720: LP64 migration: Assignment may 
overflow integer "i".