On Wed, 01 Apr 2009 07:54:20 -0700, Ian Lance Taylor <i...@google.com>
wrote:
> "Vincent R." <foru...@smartmobili.com> writes:
>
>> Now the question is can we declare a function with an eh region and will
>> it
>> construct prologue and epilogue ?
>
> The instructions are already in a function. Why do you need a separate
> prologue and epilogue for them?
>
> Maybe I am missing the point here. It seems to me that the __except
> keyword as you described it can be implemented by a transformation from
> C++ to C++. gcc already knows how to handle exception regions; you
> don't have to teach it anything in that area. You just have to generate
> the correct GIMPLE or GENERIC in the frontend. You are talking about
> creating a new function, but I just don't see any reason to do so. You
> already have a function, and you can just create exception regions in
> that function. The code in the exception region can call other
> functions, etc. What am I missing?
>
> Ian
Yes I think I don't explain things very clearly, so what is important to
know is that the __except keyword
can be passed instructions(case 1) or directly a function(case 2).
in the case 1) ie if you declare something like :
...
__except( printf("hello gcc"), 1)
and I look at asm generated I can notice that the instructions inside the
patenthesis will be put inside a function
because I can notice a prologue and epilogue.
int main()
{
...
__except(puts("in filter"), EXCEPTION_EXECUTE_HANDLER)
{
...
}
} // main
...
So on a arm plateform here is the annoted asm (asm + source code), I have
only pasted the __except part :
And we can see that just after the closing } for main there is a prologue
followed by the instructions
originally in the __except and then the epilogue.
// main }
; 128 : __except(puts("in filter"), EXCEPTION_EXECUTE_HANDLER){
str lr, [sp, #-4]! <<<< function prologue
|$...@wmain|
|$l...@wmain|
ldr r0, [pc, #8]
bl puts
mov r0, #1
|$...@wmain|
ldr pc, [sp], #4 <<<< function epilogue
so instructions inside __except parenthesis are put in something that looks
like a function
Do I need to explain more ?
