Hi,
On Wed, Jun 07, 2023 at 08:34:06AM +0800, Zhangjin Wu wrote:
> > Hi Zhangjin,
> >
> > On 2023-06-06 16:17:38+0800, Zhangjin Wu wrote:
> > > Use __syscall() helper to shrink 252 lines of code.
> > >
> > > $ git show HEAD^:tools/include/nolibc/sys.h | wc -l
> > > 1425
> > > $ git show HEAD:tools/include/nolibc/sys.h | wc -l
> > > 1173
> > > $ echo "1425-1173" | bc -l
> > > 252
> > >
> > > Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx>
> > > ---
> > > tools/include/nolibc/sys.h | 336 +++++--------------------------------
> > > 1 file changed, 42 insertions(+), 294 deletions(-)
> > >
> > > diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> > > index f6e3168b3e50..0cfc5157845a 100644
> > > --- a/tools/include/nolibc/sys.h
> > > +++ b/tools/include/nolibc/sys.h
> > > @@ -108,13 +108,7 @@ int sys_chdir(const char *path)
> > > static __attribute__((unused))
> > > int chdir(const char *path)
> > > {
> > > - int ret = sys_chdir(path);
> > > -
> > > - if (ret < 0) {
> > > - SET_ERRNO(-ret);
> > > - ret = -1;
> > > - }
> > > - return ret;
> > > + return __syscall(chdir, path);
> >
> > To be honest I'm still not a big fan of the __syscall macro.
> > It's a bit too magic for too little gain.
> >
> > The commit message argues that the patches make the code shorter.
> >
> > However doing
> >
> > __sysret(sys_chdir(path));
> >
> > instead of
> >
> > __syscall(chdir, path);
> >
> > is only three characters longer and the same amout of lines.
> >
>
> Yeah, I do like your version too, it looks consise too, the only not
> comfortable part is there are dual calls in one line.
For those who want to debug, having less macros or magic stuff is always
better, and in this essence I too find that Thomas' version is more
expressive about what is being done. Also, if some syscalls require a
specific handling (e.g. mmap() needs to return MAP_FAILED instead), it's
much easier to change only the code dealing with the return value and
errno setting than having to guess how to reimplement what was magically
done in a macro.
> > Otherwise we would have syscall() _syscall() and __syscall() each doing
> > different things.
> >
>
> Yes, I'm worried about this too, although the compilers may help a
> little, but it is too later.
The issue is for the person who remembers "I need to use 'syscall'" but
never remembering the number of underscores nor the variations.
> Just brain storming, What about another non-similar name, for example,
> __syswrap() or __sysin() ?
>
> Or even convert __sysret() to __sysout() and __syscall() to __sysin(),
> do you like it? or even __sysexit(), __sysentry(), but the __sysexit()
> may be misused with sys_exit().
I'd rather use "__set_errno()" to explicitly mention that it's only
used to set errno, but sysret would be fine as well IMHO as if we're
purist, it also normalizes the return value.
> /* Syscall return helper, set errno as -ret when ret < 0 */
> static __inline__ __attribute__((unused, always_inline))
> long __sysout(long ret)
> {
> if (ret < 0) {
> SET_ERRNO(-ret);
> ret = -1;
> }
> return ret;
> }
>
> /* Syscall call helper, use syscall name instead of syscall number */
> #define __sysin(name, ...) __sysout(sys_##name(__VA_ARGS__))
>
> static __attribute__((unused))
> int brk(void *addr)
> {
> return __sysout(sys_brk(addr) ? 0 : -ENOMEM);
> }
>
> static __attribute__((unused))
> int chdir(const char *path)
> {
> return __sysin(chdir, path);
> }
I still don't find this intuitive at all.
> If we really want something like __syscall()/__sysret(), I do think they
> should be a pair ;-)
Then one being called "call" while the other one being "ret" do form a
pair, no ?
Thanks,
Willy
