Re: [Mingw-users] Linux dirent->d_type ... Windows equivalent? [OT]

[Boyd, T. M. <tm...@cc...>]

> -----Original Message-----
> From: min...@li... [mailto:mingw-users-
> bo...@li...] On Behalf Of Tuomo Latto
> Sent: Thursday, June 05, 2008 4:49 PM
> To: MinGW Users List
> Subject: Re: [Mingw-users] Linux dirent->d_type ... Windows
equivalent?
> [OT]
> 
> Boyd, Todd M. wrote:
> > [code]
> > struct dirent ** namelist;
> [...]
> > qsort(namelist, n, sizeof(struct dirent), alphaDirSort);
>                       ^^^^^^^^^^^^^^^^^^^^^
> 
> It's an array of pointers, not an array of structs.
> 
> Also, your debug prints might have buffering issues.
> I prefer fprintf() with stderr and strings ending with a newline.
> Using fflush() won't hurt either, except performance-wise.

You're right about the buffering issues. I've been using fprintf(stderr,
x, x) now, and the "Inside alphaDirSort" was displayed. Using this
debugging mechanic, I've discovered that it's how I'm dereferencing the
dirent pointers in alphaDirSort. I've changed it from:

alphaDirSort(const void *, const void *);

to:

alphaDirSort(const struct dirent *, const struct dirent *);

In order to try and ease some of my confusion, but it didn't really do
anything for me except spare me from casting them later. I have tried
several ways trying to access the d_name member. All of them return
garbage rather than the d_name (or are invalid operations).

Given struct dirent * a:

puts(a->d_name);		// garbage
puts(a.d_name);		// err: not a structure or union
puts((*a).d_name);	// garbage
puts((*a)->d_name);	// err: invalid type argument of ->
puts((&a).d_name);	// err: not a structure or union
puts((&a)->d_name);	// err: not a structure or union

Changing the namelist malloc line to reflect pointers to dirents instead
of dirents caused an error and munmap_chunk() to be run. alphaDirSort()
returned the same garbage, regardless of if qsort() was told to handle
pointers or structs. I think I need to do a bit more research on
qsort(). Since I am passing it a valid array that can be accessed in a
"normal" way (using [] index specifiers), there should be some code out
there that will explain to me the proper method for accessing the values
passed through qsort() to whatever comparison function it will use.

I'll do research on my own, as I've obviously missed some critical
information about qsort(), and I'm out of practice dealing with
pointers.

Thanks anyway (and sorry for clogging the listserv),


Todd Boyd
Web Programmer