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Re: 32 bit vs 64 bit Cygwin, followup




Please, no top-posting.

On Nov 28 11:06, Sam Habiel wrote:
> Yaakov,
> 
> On Wed, Nov 28, 2018 at 11:01 AM Yaakov Selkowitz <yselkowi@xxxxxxxxxx> wrote:
> >
> > On Mon, 2018-11-26 at 14:07 -0500, Sam Habiel wrote:
> > > Hello everybody,
> > >
> > > In this message
> > > (https://www.sourceware.org/ml/cygwin/2018-11/msg00190.html), Corinna
> > > (Hi Corinna!) says:
> > >
> > > "Don't do that.  Use 64 bit Cygwin whenever possible.  32 bit is a lost cause."
> > >
> > > I would like to mention why I am still using 32 bit Cygwin.
> > >
> > > I maintain a port of a database called GT.M
> > > (https://en.wikipedia.org/wiki/GT.M) on Cygwin. I work with Electronic
> > > Medical Records that run on this database. GT.M contains a large
> > > amount of assembly code, written to run on the x32 Linux ABI and the
> > > AMD x64 ABI. It's was very easy to get the x32 Linux ABI to run on
> > > Cygwin x32; Cygwin x64 on the other hand uses the Windows x64 ABI,
> > > which is very different than the AMD ABI (more detail here:
> > > https://eli.thegreenplace.net/2011/09/06/stack-frame-layout-on-x86-64/).
> > > I don't have the expertise nor the time to rewrite a lot of assembly
> > > code to use the Windows x64 ABI. There are about 100 source code files
> > > that are in assembly.
> >
> > -mabi=sysv ?
> >
> Are you telling me that gcc has a flag to support AMD ABI on Cygwin
> x64? The assembly code is not standalone; it gets called from C code
> and calls C code.

That's what he's telling you.  However, you have to interact with the MS
ABI(*) as well as soon as you call external library functions so it
makes sense to keep your C code in MS ABI.  For the assembler functions,
you can just tell the compiler they are in SYSV ABI by adding a function
attribute to the declaration:

int asm_func (args) __attribute__ ((sysv_abi))

Good luck,
Corinna

(*) Just keep in mind that Cygwin is LP64, not LLP64:
    https://cygwin.com/faq/faq.html#faq.programming.64bitporting

-- 
Corinna Vinschen
Cygwin Maintainer

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