Re: [PATCH] tools/ocaml/Makefile.rules: use correct C flags when compiling OCaml C stubs

[Edwin Torok <edwin.torok@xxxxxxxxx>]

> On 25 Oct 2023, at 15:02, Christian Lindig <christian.lindig@xxxxxxxxx> wrote:
> 
> 
> 
>> On 25 Oct 2023, at 14:52, Edwin Török <edvin.torok@xxxxxxxxxx> wrote:
>> 
>> From: Edwin Török <edwin.torok@xxxxxxxxx>
>> 
>> The code currently uses GCC to compile OCaml C stubs directly,
>> and although in most cases this works, it is not entirely correct.
>> 
>> This will fail if the OCaml runtime has been recompiled to use and link with 
>> ASAN for example
>> (or other situations where a flag needs to be used consistently in 
>> everything that is linked into the same binary).
>> 
>> Use the OCaml compiler instead, which knows how to invoke the correct C 
>> compiler with the correct flags,
>> and append the Xen specific CFLAGS to that instead.
>> 
>> Drop the explicit -fPIC and -I$(ocamlc -where): these will now be provided 
>> by the compiler as needed.
>> 
>> Use -verbose so we see the actuall full C compiler command line invocation 
>> done by the OCaml compiler.
>> 
>> Signed-off-by: Edwin Török <edwin.torok@xxxxxxxxx>
> 
> Acked-by: Christian Lindig <christian.lindig@xxxxxxxxx>
> 
> I like using the OCaml compiler to compile stubs as it knows how to handle C 
> files and will invoke the C compiler with the correct flags. However, this is 
> the kind of change that would be good to have tested on all supported 
> platforms. I therefore invite comments from those who maintain the build 
> process.


There was a CI failure. I've pushed an updated version of this patch here:
https://gitlab.com/xen-project/people/edwintorok/xen/-/commit/137ffad324eb82884e7ac6f46f618459d365693e

If it passes the CI this time I'll send out a V2, looks like the -fPIC flag is 
needed on some platforms and is not automatically added by the OCaml compiler.


Best regards,
--Edwin