klibc - Jun 2018 - [PATCH] kbuild: add -ffreestanding to required flags

New clang versions need the '-ffreestanding' flag because new changes
convert
system calls to their unlocked versions, which don't exist in the kernel
library.

Signed-off-by: Bill Wendling <morbo at google.com>

diff --git a/scripts/Kbuild.klibc b/scripts/Kbuild.klibc
index f500d535..9cf4b2d9 100644
--- a/scripts/Kbuild.klibc
+++ b/scripts/Kbuild.klibc
@@ -67,7 +67,8 @@ include $(srctree)/scripts/Kbuild.include
 #
---------------------------------------------------------------------------

 KLIBCREQFLAGS     := $(call cc-option, -fno-stack-protector, ) \
-                     $(call cc-option, -fwrapv, )
+                     $(call cc-option, -fwrapv, ) \
+                     $(call cc-option, -ffreestanding, )
 KLIBCARCHREQFLAGS : KLIBCOPTFLAGS     : KLIBCWARNFLAGS    := -W -Wall
-Wno-sign-compare -Wno-unused-parameter

-- 
Bill Wendling | SWE | wcw <morbo at google.com>@google.com <morbo at
google.com> |
 408-921-0157
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Bill Wendling dixit:
>New clang versions need the '-ffreestanding' flag because new
changes
>convert system calls to their unlocked versions, which don't exist in
>the kernel library.
This is probably wrong, a libc is not, in contrast to a bootloader
or kernel, a freestanding environment.

For the case of GCC, -ffreestanding is definitely wrong.

Please look for another solution, e.g. teach clang that klibc
does not have those unlocked calls. (AIUI klibc only supports
GCC officially anyway?)

bye,
//mirabilos
-- 
?It is inappropriate to require that a time represented as
 seconds since the Epoch precisely represent the number of
 seconds between the referenced time and the Epoch.?
	-- IEEE Std 1003.1b-1993 (POSIX) Section B.2.2.2

They way to indicate to clang that those calls shouldn't be lowered to
their unlocked versions is to mark it as freestanding. Freestanding simply
means that the standard C library can't be assumed to be available,
which in this case it's not because you're creating the C library. So
I'm not sure what other solution you wish to see here (apart from
implementing the unlocked versions in klibc, which I don't think you
want).

Could you explain why this is wrong for GCC?

-bw

On Wed, Jun 6, 2018 at 4:35 AM Thorsten Glaser <tg at mirbsd.de> wrote:
> Bill Wendling dixit:
>
> >New clang versions need the '-ffreestanding' flag because new
changes
> >convert system calls to their unlocked versions, which don't exist
in
> >the kernel library.
>
> This is probably wrong, a libc is not, in contrast to a bootloader
> or kernel, a freestanding environment.
>
> For the case of GCC, -ffreestanding is definitely wrong.
>
> Please look for another solution, e.g. teach clang that klibc
> does not have those unlocked calls. (AIUI klibc only supports
> GCC officially anyway?)
>
> bye,
> //mirabilos
> --
> ?It is inappropriate to require that a time represented as
>  seconds since the Epoch precisely represent the number of
>  seconds between the referenced time and the Epoch.?
>         -- IEEE Std 1003.1b-1993 (POSIX) Section B.2.2.2
>
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