Re: [seL4] Try two for libsel4 not having a dependency on libc

3 Jul 2015

      Moving sel4_benchmark.h into libsel4 was something I was thinking we might
do. I'm thinking longer maybe it could significantly expand and possibly
have supporting c sources so that's why I kept it separate for now.

On using error rather than message, NP, I chose message because I didn't
want to always force people to change the configuration, but maybe that
would be error is better.

Some what related, I've chosen to always assume putchar would be available
in some configurations, so I created
sel4_debug_printf.h/sel4_debug_assert.h which uses NDEBUG to conditionally
turn off/on asserts and printf. Where as sel4_printf.h/sel4_assert.h
assumes putchar would always be available. So this a different behavior
then previously and people may not like it.

As I said, still quite a bit to discuss and of course, the main one: is
having libsel4 independent of libc something that's desirable? Which,
obviously you don't think it is, but others seem to like it, so we'll see
what happens.
-- Wink

On Thu, Jul 2, 2015, 5:25 PM Matthew Fernandez <
matthew.fernandez@nicta.com.au> wrote:
...
Though I'm still opposed to this change overall, my two cents on the
current state:
- Should we just put the benchmarking code in libsel4bench [0]? I
realise the former is for
benchmarking the kernel and the latter is (arguably) for benchmarking
userspace, but it seems to me
a better home for it.
- You've used `#pragma message` in one instance. I would prefer `#error`
for consistency, though
I'm aware `#pragma message` is more portable. Moreover, why are we
emitting messages here in the
first place? It's a perfectly valid (in fact the default) configuration to
have the benchmarking
syscalls disabled.
[0]: https://github.com/seL4/libsel4bench
...
One other note, this isn't done. It still needs to be integrated with
muslc (libc) and at a minimum
seL4_Halt needs to be properly implemented. And I'm sure there will be
...
needed but I hope we're closer.
On Thu, Jul 2, 2015 at 5:11 PM Wink Saville > wrote:
Here https://github.com/winksaville/sel4-min-sel4/tree/no-libc3
is try #3, I've pasted the
    commit message below as it tells the story, let me know what you
On 03/07/15 10:19, Wink Saville wrote:
plenty of other changes
think:
...
libsel4 with no libc dependency.
         The primary changes are introducing sel4_types.h and removing
std* types
...
plus porting assert and printf code from the kernel to libsel4.
All of
...
this means the code within libsel4 does not overload any
typical libc
...
entities. So now libsel4 uses types like seL4_Uint32 ...
instead of
...
uint32_t. And printf is now seL4_Printf and assert is
seL4_Assert ....
...
I'm also using sel4_ prefixes for various files as I felt it
was more
...
consistent with the names of the entities within the files.
         The only new library is libsel4_benchmark and since it consists
of just
...
sel4_benchmark.h we might want to move that back into libsel4.
I would
...
have liked to move out libsel4_assert, libsel4_printf and
libsel4_putchar
...
but since asserts are used by low level generated code I
couldn't come up
...
with a good way of doing that.
         Finally, the only file modified that effects kernel code is
         kernel/tools/bitfield_gen.py. It needed to be modified as it
generates
...
files for both kernel and user space. And for user space the
generated code
...
(types_gen.h) needed to use the new types and asserts. The
changes should
...
not change what is generated for the kernel and I did a
comparison of
...
kernel_final.{c|s} before and after my change and the only
differences
...
were time stamps
-- Wink
On Mon, Jun 29, 2015 at 7:07 PM Wink Saville 
mailto:wink@saville.com> wrote:
...
Will do.
On Mon, Jun 29, 2015, 7:05 PM Anna Lyons <
Anna.Lyons@nicta.com.au
...
mailto:Anna.Lyons@nicta.com.au> wrote:
Hi,
>
             > Currently there is at least one known problem, I modified
             > bitfield_gen.py so types_gen.h has no asserts since at
the moment the
...
> kernel uses assert and userspace is libsel4_assert. We
could either do
...
> something like I've done and remove them or change the
kernel to use
...
> libsel4_assert or something else.
             >
The asserts are really important to avoid horrible bugs when
using
...
functions created by the bitfield generator, so if we go
ahead with this
...
let's make sure they survive in some form.
Cheers,
            Anna.
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