Re: stack allocation and gcc

[Ihar 'Philips' Filipau]

Richard B. Johnson wrote:
> The caller expects that the space for the second set of local
> variables in the second program unit is not allocated until the
> program unit is entered.
>
> I don't know why he would expect this behavior. Certainly

   It was my first thought actually - when I have started typeing in 
e-mail.

   When I have reached half e-mail - I have understood that this is 
simple performance consideration - stack space is allocated once.

   I have tryed to convert my e-mail to another issue - but seems I did 
it not good enough :-)

   But then I realized that my thinking was wrong - I'm using variables 
in different never overlapping contextes. But space allocated for 
everyone. "if (..) { int i; }; if (...) { int i; }" will result not in 
sizeof(int) stack space allocated - but in sizeof(int)*2.

   It seems that gcc check size required by all top level contextes in 
function - it checks for "if { int a[16] } else { int a[16] }" - space 
allocated correctly.
   But 'if () { int a[16]; }; if () { int a[16] };' seems to break 
something, and sum of the sizes for both if()'s spaces finishes 
allocated on stack. And this was the case with macro in my module.

   I doubt I can write competent report/query to gcc mail list - 
probably it is worth to ask there.

--
Ihar 'Philips' Filipau  / with best regards from Saarbruecken.
--                                                           _ _ _
 "... and for $64000 question, could you get yourself       |_|*|_|
   vaguely familiar with the notion of on-topic posting?"   |_|_|*|
                                -- Al Viro @ LKML           |*|*|*|
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