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Re: statement expressions and extended asm bug?
Nathan Sidwell wrote:
> inline int foo (int arg_)
> {
> int result __asm("d0");
> int arg __asm("d1"); // for sake of argument
>
> arg = arg_;
> asm ("call whereever": "=r(result)" :"r(arg)" : ...);
>
> return result;
> }
>
> This is subtly different from the statement expression form, because
> the result of a C statement expression can be an lvalue, whereas here
> it is an rvalue. (in g++, statement expressions always produce a result
> 'as-if' by 'return').
More to the point, calling the foo(arg) above from different function
arguments isn't a sequence-point violation, unlike calling the
statement-expressions.
function(foo(arg1), foo(arg2));
could evaluate the two calls to foo() in either order, but it must
finish one completely before the other.
Perhaps this is a flaw in GCC's implementation of
statement-expression, because s-e is intended for use in macros
function-like macros -- whose callers don't know they are calling a
macro.
-- Jamie