RFC: types conflicts

[Peter Mamonov]

Hello, Ahmad,

On Wed, Jul 08, 2020 at 10:02:00AM +0200, Ahmad Fatoum wrote:
> Hello Peter,
> 
> On 7/7/20 3:56 PM, Peter Mamonov wrote:
> > Hello,
> > 
> > I tried to build MicroPython using barebox toolchain and found a number of
> > conflicts between barebox and compiler headers. Below you will find the patch
> > which demostrates some of them. In this particular example the problem arises
> > due to simultaneous inclusion of some compiler headers along with barebox
> > version of `strings.h`, which in turn includes barebox analogs of those headers
> > from `include/linux`. I belive there should be a segregation between headers in
> > `include` and in `include/linux`, i.e. headers from `include/` should not
> > reference <linux/*.h> headers. Yet I understand this is somewhat problematic.
> > What do you think?
> 
> barebox code shouldn't make use of any compiler headers at all, except for <stdarg.h>.
> The only exception are arch/sandbox/os and scripts/, which reference libc headers.
> Everything else should comes out of barebox' include/ directory.
> 
> If you have foreign code that you want to port into barebox, either modify it
> to use barebox headers or change the include order when building it to use _local_
> versions of the headers it requires.

Ok, I've got your point. Yet I want to point out that addition of *unmodified* 
code in a form of git submodule would greatly simplify further support of this 
port. Unfortunately modifying include order will not help in this case, since, 
for example, both `barebox/include/linux/stddef.h` (included from 
`barebox/include/string.h` via <linux/string.h>, etc.) and 
`/usr/lib/gcc-cross/<ARCH>-linux-gnu/X/include/stdbool.h` define `true`/`false` 
macros. On the other hand `/usr/include/linux/stddef.h` and 
`/usr/lib/gcc/<ARCH>-linux-gnu/X/include/stdbool.h` coexist in GNU/Linux system 
nicely, since no header from `/usr/include/` does reference <linux/*.h> 
headers.

> > diff --git a/commands/types_conflict.c b/commands/types_conflict.c
> > new file mode 100644
> > index 0000000000..70fee8d6f4
> > --- /dev/null
> > +++ b/commands/types_conflict.c
> > @@ -0,0 +1,12 @@
> > +#include <stdbool.h>
> > +#include <stdint.h>
> > +#include <stddef.h>
> > +
> > +#include <string.h>
> 
> barebox (except sandbox) is meant to be compiled with freestanding C implementations
> that aren't required to provide a <string.h>. So no barebox code should depend on
> compiler-provided <string.h>.

Actually `string.h` comes from barebox's `include/` dir, while `std*.h` come 
from compiler's include dir. 


PS: By the way, do you think Barebox will benefit from importing MicroPython 
(https://micropython.org/) and exposing some of Barebox APIs to it?

Regards,
Peter