Re: [RFC] test-lib.sh: No POSIXPERM for cygwin

> Torsten Bögershausen <tboegi@web.de> writes:
>
>> Use a compile switch IGNORECYGWINFSTRICKS to disable the usage
>> of cygwin_lstat_fn() only in path.c
>
> The analysis of the problem and the basic idea to disable the
> fast-but-lying fstricks in the code that matters may be good, but
> the implementation is questionable.
>
> What if we later need to move functions around, etc., so that some
> other calls in path.c still do want to use the fstricks bit while
> the existing ones in the file want the real lstat() information?
>
> Actually, that already is the case.  The call to lstat() in
> validate_headref() only cares about the S_ISXXX() type and can
> afford to use the fast-and-lying one, no?
>
> How about doing something like this in the generic codepath, and
> implement your own cygwin_true_mode_bits() function at the cygwin
> compatibility layer, and add
>
>     #define true_mode_bits cygwin_true_mode_bits
>
> in the compat/cygwin.h file?  The change has the documentation value
> to clarify what each lstat() is used for, too.
>
> Ideally, the "#ifndef true_mode_bits" part may want to become a
> generic helper function if there are lstat() calls in other files
> that cygwin wants to use the real lstat() not the fast-but-lying
> one, but one step at a time.
>
> Hrm?
>
>  path.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/path.c b/path.c
> index d3d3f8b..d0b31e5 100644
> --- a/path.c
> +++ b/path.c
> @@ -14,6 +14,21 @@
>  #include "strbuf.h"
>  #include "string-list.h"
>  
> +#ifndef true_mode_bits
> +/*
> + * The replacement lstat(2) we use on Cygwin is incomplete and
> + * lies about permission bits; most of the time we do not care,
> + * but the callsites of this wrpper do care.
> + */
> +static int true_mode_bits(const char *path, int *mode)
> +{
> +	struct stat st;
> +	if (lstat(path, &st) < 0)
> +		return -1;
> +	return st.st_mode;

> +}
> +#endif
> +
>  static char bad_path[] = "/bad-path/";
>  
>  static char *get_pathname(void)
> @@ -400,9 +415,8 @@ int set_shared_perm(const char *path, int mode)
>  		return 0;
>  	}
>  	if (!mode) {
> -		if (lstat(path, &st) < 0)
> +		if (true_mode_bits(path, &mode) < 0)
>  			return -1;
> -		mode = st.st_mode;
>  		orig_mode = mode;
>  	} else
>  		orig_mode = 0;