proposal: add -Werror-implicit-function-declaration to the default optflags

[Dave Jones]

On Mon, Mar 24, 2008 at 10:03:30PM +0100, Hans de Goede wrote:
 > Hi all,
 > 
 > This is a new thread spawning from the "3.6% of heads up: Please correct your 
 > #includes or optflags use" thread.
 > 
 > I would like to propose to add "-Werror-implicit-function-declaration" to the 
 > default optflags. Why? Because missing prototypes can cause all sorts of problems:
 > 
 > Anything (any function) that returns a pointer, will be a problem when compiled 
 > on 64 bit without a prototype, as the compiler will assume the return type is 
 > an int, and then cast that to a pointer as needed.
 > 
 > Anything returning a float / double will be a problem regardless of 32/64 bits 
 > as only 32 bits of the returned floating point number will be taken and 
 > interpreted as an int (and then cast back to a float / double if used as such).
 > 
 > Any function called with arguments of different type then expected (for example 
 > a float, where the function expects an int or visa versa) will have the same 
 > problem.
 > 
 > Which is why I say: fix them all.

I agree with the sentiment, but I don't think the timing is right.
This really needs to be done right after a release, so we've got plenty of
time to fix some of them.  It isn't always as simple as "just add a #include".
I looked into some of the warnings coming from the X server a month or so ago,
and there's what appears to be some pretty icky layering violations.

Going from "this really shouldn't be doing that" to "this doesn't build any more"
and adding a ton of work to peoples plates right before we ship a release
sounds like a guaranteed way to make sure we miss the release date.

	Dave

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