RFC: [PATCH] Make -static builds work again without crashing
Maarten Lankhorst
m.b.lankhorst at gmail.com
Mon Apr 14 17:11:20 UTC 2008
Hello Denys,
2008/4/14, Denys Vlasenko <vda.linux at googlemail.com>:
> On Monday 14 April 2008 05:06, Maarten Lankhorst wrote:
> > Hi all,
> >
> > After some experimenting I came to the conclusion that the minimum app
> > that won't crash with gcc -static is printf("%.0d", 0); which is
> > essentially a noop printf. So my patch calls that before calling main.
> >
> > Looking for feedback on the patch.
>
>
> ?!
>
> Ths will force stdio to be linked it into every application.
>
> How about fixing the problem instead of papering over it?
>
> I think the possible reason is that _stdio_init is a weak symbol:
>
> extern void weak_function _stdio_init(void) attribute_hidden;
>
> and here we check that it was linked in, only if it was, we run it:
>
> /*
> * Initialize stdio here. In the static library case, this will
> * be bypassed if not needed because of the weak alias above.
> * Thus we get a nice size savings because the stdio functions
> * won't be pulled into the final static binary unless used.
> */
> if (likely(_stdio_init != NULL))
> _stdio_init();
>
> But current gcc assumes (and it's allowed by C standard) that function
> address is never NULL. So it optimizes away this if(), and calls
> _stdio_init() unconditionally. If it indeed is NULL, we crash.
I don't think this is the issue here, if I remove the call to
_stdio_init call in __uClibc_init it will still crash.
Cheers,
Maarten.
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