Re: egcs, RFC: patch for possible -Wmissing-noreturn warning

["Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu>]

 > From: Martin Mares <mj@ucw.cz>
 > 
 > Hello,
 > 
 > > 	Looking at these functions, they clearly fall off their ends.  Eg:
 > > 
 > >  > static inline void
 > >  > fde_insert (fde_accumulator *accu, fde *this_fde)
 > >  > {
 > >  >   accu->linear.array[accu->linear.count++] = this_fde;
 > >  > }
 > > 
 > > 	So why is the test flagging them? Is there another bit I need to
 > > check besides:
 > > current_function_returns_null && current_function_returns_value ??
 > 
 > It is not as simple as it might look on the first sight. It's easy
 > to prove there exists _no_ algorithm distinguishing functions that
 > really return.
 > 
 > [...]
 > 
 > There are three possible cases:
 > 
 > [1] Functions that contain no jumps. They always return and there
 > is nothing to check.
 > -- 
 > Martin `MJ' Mares   <mj@ucw.cz>   http://atrey.karlin.mff.cuni.cz/~mj/

	Yes, but IMHO, this isn't the halting problem.  Its not
whether it *will* return but whether its *possible* to return.  Ie,
what are the exit points of the function?  Does it `return', fall off
its end or call abort/exit/longjmp/{some other `noreturn' function}?

	If its only the first two, or some combination of all three,
its *possible* to return.  If its only the third case, then its a
`noreturn' function.

	Gcc has code to detect this stuff and its failing in the above
case which is a one line assignment statement.  Clearly this static
inline function returns.  So I'm convinced its either a bug or I'm not
checking all the appropriate bits. 

		--Kaveh
--
Kaveh R. Ghazi			Engagement Manager / Project Services
ghazi@caip.rutgers.edu		Icon CMT Corp.