Re: [RFC] Linux system call builtins

[Florian Weimer <fweimer@redhat.com>]

* Matheus Afonso Martins Moreira via Gcc:

>   + It's stable
>
>         This is one of the things which makes Linux unique
>         in the operating system landscape: applications
>         can target the kernel directly. Unlike in virtually
>         every other operating system out there, the Linux kernel
>         to user space binary interface is documented[2] as stable.
>         Breaking it is considered a regression in the kernel.
>         Therefore it makes sense for a compiler to target it.
>         The same is not true for any other operating system.

There is quite a bit of variance in how the kernel is entered.  On
x86-64, one once popular mechanism is longer present in widely-used
kernels.  For POWER, the preferred way changed over time.  Likewise for
i386.

>   + It's a calling convention
>
>         GCC already supports many calling conventions
>         via function attributes. On x86 alone[3] there's
>         cdecl, fastcall, thiscall, stdcall, ms_abi, sysv_abi,
>         Win32 specific hot patching hooks. So I believe this
>         would not at all be a strange addition to the compiler.

But using a builtin obfuscates that relationship.  There is no
__builtin_call_ms_abi, is there?

Thanks,
Florian