Eric Wong <e...@80x24.org> writes:

> O_CLOEXEC only exists since Linux 2.6.23 and there are likely
> still LTS (CentOS 5.x?) and non-Linux systems which do not have
> it, as well as machines with could have it defined in userspace
> headers but not have it in the kernel.
>
> So I suggest something like the following: (untested)
>
> #define GIT_O_TMP (O_RDWR | O_CREAT | O_EXCL)
>
> #ifndef O_CLOEXEC
> #  define O_CLOEXEC 0
> #endif
>       /* state: -1=unknown; 0=broken; 1=working */
>       static int cloexec_state = O_CLOEXEC == 0 ? 0 : -1;
>       static int GIT_O_ETMP = (GIT_O_TMP | O_CLOEXEC)
>
>       int fd = open(filename, GIT_O_ETMP, 0666);
> ...
>       /*
>        * This is racy in the presence of threads,
>        * but the best we can do for old *nix:
>        */
> #if defined(F_GETFD) && defined(F_SETFD) && defined(FD_CLOEXEC)
>       if (fd >= 0 && cloexec_state != 1) {
>               int flags = fcntl(fd, F_GETFD);
>
>               if (flags == -1)
>                       die_errno("F_GETFD failed");
>               if (flags & O_CLOEXEC)
>                       cloexec_state = 1;
>               else {
>                       flags = fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
>                       if (flags == -1)
>                               die_errno("F_SETFD failed");
>                       cloexec_state = 0;
>
>               }
>       }
> #endif
>       ...

Our codepaths themselves generally do not care about O_CLOEXEC, so
giving a racy emulation of it is not worth the effort, making the
later half of the above an overkill.  Perhaps the three lines to
define O_CLOEXEC to 0 on older UNIX might be sufficient.
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