2012/8/8 niXman
> 2012/8/8 Ruben Van Boxem:
> > That's not what was implemented. What was implemented is the
> > native (MSVC compatible?) Win64 native exception handling.
> Why Win64? SEH that, only for Win64 is implemented/works?
>
> P.S.
> Probably my questions seem silly, but I never worked for windows.
> Some years I work as the programmer for Linux, and never thought about
> on how are implemented an exceptions and how many implementations
> exist =)
>
It's not silly, it's actually quite a tale:
0. For MSVC, there are three exception handling models:
http://msdn.microsoft.com/en-us/library/1deeycx5%28v=vs.110%29.aspx
1. SEH for C++ exceptionsas implemented in MSVC for 32-bit is patented.
2. Win64 exception handling is half-documented, and is based on this family
of functions: http://msdn.microsoft.com/en-us/library/ms680615%28v=vs.85%29which
are only supported on Win64 (as you can see on that msdn page)
3. GCC has several exception handling models, among which dw2 and sjlj.
- dw2 is used on Linux as it is something called "zero-cost exception
handling". This means before a C++ "try" block is entered or a function is
called, nothing needs to be done at runtime. The compiler can generate all
necessary stack unwind info at compile time.
- In the sjlj model, which MinGW-w64 recommended for both 32 and 64 bit,
requires a preparation function each time a function is called and/or a try
block is entered. This is not "zero-cost".
- dw2 exceptions cannot propagate through foreign (MSVC compiled) code, so
you could not throw a dw2 exception across a Microsoft compiled DLL.
- sjlj exceptions work in this use case. dw2 ex
4. Win64 eh is very similar to dwarf exceptions, it is also a "zero-cost"
model (often implemented as "table based" eh).
There are other implementations and details I'm getting wrong or omitting,
but this is the story I keep in my head.
>
>
> > It is something like the dw2/sjlj eh, but better: it allows MSVC-code
> > originating exceptions to be thrown over GCC generated code and I would
> > guess vice versa. sjlj does this as well, but this seh does it without
> > performance penalty.
> What it is more preferable to development for windows?
>
see above, dw2 vs sjlj is a performance vs
throw-exceptions-across-foreign-code tradeoff.
Whether it is possible to argue, what SEH always the most preferred choice?
>
The Win64 SEH based C++ EH is always preferred. It is superior to dw2
because it works on x64, and to sjlj because it is a "zero-cost" model as
you can find explained elsewhere.
>
>
> > I have, and Jon_y has built a multilib compiler.
> It is necessary to build in some stages?
> 1) all-target-libgcc
> 2) all-gcc
> 3) all
>
> I am right?
>
I didn't need to do anything special, so I don't think so. You can
cross-compile in the following way:
1. headers+binutils
2. all-gcc
3. crt
4. rest of gcc (including libgcc)
Cheers,
Ruben
PS: if I said something completely wrong, please correct me!
>
> P.P.S.
> Please, delete my e-mail when answering ;)
> Thanks.
>
> --
> Regards,
> niXman
> ___________________________________________________
> Dual-target(32 & 64 bit) MinGW compilers for 32 and 64 bit Windows:
> http://sourceforge.net/projects/mingwbuilds/
>
>
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