Re: [RFC PATCH] gc --auto: don't lie about running in background on Windows

[Junio C Hamano <gitster@pobox.com>]

SZEDER Gábor <szeder@ira.uka.de> writes:

> Arguably this helper function could be just a simple variable.  I
> opted for a function because:
>
>   - I preferred a single '#ifdef NO_POSIX_GOODIES', and putting a
>     static variable so near to EOF felt just wrong.  (And this is why
>     it's not an inline-able function defined in a header file.)
>
>   - currently we know already at compile time that Windows can't
>     daemonize, but in the future we might want to extend this helper
>     function to perform some runtime checks, too.  But this is perhaps
>     like preparing for crossing a bridge where we'll never get to.

Alternatively, the implementation of daemonize() and can_daemonize()
can live in compat/ and have the #ifdef switch in git-compat-util.h,
e.g. something along the lines of these:

	<< git-compat-util.h >>
	... after conditional inclusion of compat/mingw.h ...
	#ifndef can_daemonize
        #define can_daemonize() 1
	#endif
        
	<< compat/mingw.h >>
	#define can_daemonize() 0
	#define daemonize() mingw_daemonize()

	<< setup.c >>
        ...
        #ifndef NO_POSIX_GOODIES
        int daemonize(void)
        {
            ... no ifdef around here ...
	}
	#endif

We can be even more purist and move the daemonize() implementation
for POSIX to compat/posix.c to keep the generic part even more
platform agnostic, which would remove the only #ifdef in setup.c,
but that might be going a bit too far.

These possible implementation choices aside, the goal of this patch
is a worthwhile thing to do, I would think.

Thanks.

>  builtin/gc.c |  1 +
>  cache.h      |  1 +
>  setup.c      | 17 +++++++++++++++--
>  3 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index c583aad6ec28..79a0f6dc1126 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -368,6 +368,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>  		 */
>  		if (!need_to_gc())
>  			return 0;
> +		detach_auto &= can_daemonize();
>  		if (!quiet) {
>  			if (detach_auto)
>  				fprintf(stderr, _("Auto packing the repository in background for optimum performance.\n"));
> diff --git a/cache.h b/cache.h
> index fd728f079320..3662e5aabb98 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -524,6 +524,7 @@ extern int set_git_dir_init(const char *git_dir, const char *real_git_dir, int);
>  extern int init_db(const char *template_dir, unsigned int flags);
>  
>  extern void sanitize_stdfds(void);
> +extern int can_daemonize(void);
>  extern int daemonize(void);
>  
>  #define alloc_nr(x) (((x)+16)*3/2)
> diff --git a/setup.c b/setup.c
> index c86bf5c9fabe..6187a4ad9c47 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -1033,12 +1033,25 @@ void sanitize_stdfds(void)
>  		close(fd);
>  }
>  
> +#ifdef NO_POSIX_GOODIES
> +int can_daemonize(void)
> +{
> +	return 0;
> +}
> +
>  int daemonize(void)
>  {
> -#ifdef NO_POSIX_GOODIES
>  	errno = ENOSYS;
>  	return -1;
> +}
>  #else
> +int can_daemonize(void)
> +{
> +	return 1;
> +}
> +
> +int daemonize(void)
> +{
>  	switch (fork()) {
>  		case 0:
>  			break;
> @@ -1054,5 +1067,5 @@ int daemonize(void)
>  	close(2);
>  	sanitize_stdfds();
>  	return 0;
> -#endif
>  }
> +#endif /* #ifdef NO_POSIX_GOODIES */