Re: git: c27a89971805 - main - stdlib.h: add __noexcept to prototypes

From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Fri, 02 Feb 2024 18:59:09 UTC
On Fri, Feb 02, 2024 at 11:36:35AM -0700, Warner Losh wrote:
> On Fri, Feb 2, 2024, 11:28 AM Konstantin Belousov <kostikbel@gmail.com>
> wrote:
> 
> > On Fri, Feb 02, 2024 at 06:16:59PM +0000, Warner Losh wrote:
> > > The branch main has been updated by imp:
> > >
> > > URL:
> > https://cgit.FreeBSD.org/src/commit/?id=c27a89971805b176dcfa5a234f2ea6f6109d0a70
> > >
> > > commit c27a89971805b176dcfa5a234f2ea6f6109d0a70
> > > Author:     Lexi Winter <lexi@le-Fay.ORG>
> > > AuthorDate: 2024-02-02 16:41:40 +0000
> > > Commit:     Warner Losh <imp@FreeBSD.org>
> > > CommitDate: 2024-02-02 18:11:17 +0000
> > >
> > >     stdlib.h: add __noexcept to prototypes
> > >
> > >     The noexcept specifier is required on these functions in C++:
> > >     _Exit(), atexit(), quick_exit(), at_quick_exit(), abort().
> > >
> > >     MFC after:      2 weeks
> > >
> > >     Reviewed by: imp
> > >     Pull Request: https://github.com/freebsd/freebsd-src/pull/1085
> > > ---
> > >  include/stdlib.h | 10 +++++-----
> > >  1 file changed, 5 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/include/stdlib.h b/include/stdlib.h
> > > index ff8991d1fa94..f0687f01e6c7 100644
> > > --- a/include/stdlib.h
> > > +++ b/include/stdlib.h
> > > @@ -84,9 +84,9 @@ extern int __mb_cur_max;
> > >  extern int ___mb_cur_max(void);
> > >  #define      MB_CUR_MAX      ((size_t)___mb_cur_max())
> > >
> > > -_Noreturn void        abort(void);
> > > +_Noreturn void        abort(void) __noexcept;
> > >  int   abs(int) __pure2;
> > > -int   atexit(void (* _Nonnull)(void));
> > > +int   atexit(void (* _Nonnull)(void)) __noexcept;
> > >  double        atof(const char *);
> > >  int   atoi(const char *);
> > >  long  atol(const char *);
> > > @@ -154,7 +154,7 @@ unsigned long long
> > >        strtoull(const char * __restrict, char ** __restrict, int);
> > >  #endif /* __LONG_LONG_SUPPORTED */
> > >
> > > -_Noreturn void        _Exit(int);
> > > +_Noreturn void        _Exit(int) __noexcept;
> > >  #endif /* __ISO_C_VISIBLE >= 1999 */
> > >
> > >  /*
> > > @@ -163,9 +163,9 @@ _Noreturn void     _Exit(int);
> > >  #if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
> > >  void *       aligned_alloc(size_t, size_t) __malloc_like
> > __alloc_align(1)
> > >           __alloc_size(2);
> > > -int  at_quick_exit(void (*)(void));
> > > +int  at_quick_exit(void (*)(void)) __noexcept;
> > >  _Noreturn void
> > > -     quick_exit(int);
> > > +     quick_exit(int) __noexcept;
> > This is wrong, libc quick_exit() does not provide such guarantees as
> > implemented. More, being part of libc it cannot ever guarantee that ever
> > (and call std::terminate if the requirement is violated).
> >
> > Making it such would require bringing some C++ ABI into libc which I
> > object strongly.
> >
> 
> So is this just for quick_exit, or all the functions marked?
Other functions are abort()/_Exit()/atexit(). No functions in this list
call a user-provided functions, so they cannot raise exceptions.

My objection is only against our quick_exit().

> 
> Warner
> 
> 
> > >  #endif /* __ISO_C_VISIBLE >= 2011 */
> > >  /*
> > >   * Extensions made by POSIX relative to C.
> >