Re: [Chicken-hackers] [PATCH] handle EOVERFLOW and ENOTDIR gracefully in file/directory-exists?

[Alan Post]

On Sat, Oct 08, 2011 at 03:11:29PM +0200, Felix wrote:
> This patches avoids an error when "[file|directory]-exists?"  gets
> EOVERFLOW or ENOTDIR, which indicate an existing or no-existing file,
> respectively.
> 
> 
> cheers,
> felix
> 
> 

> commit 473edf9428a7bc38fc033e86d0bbcb362f1cd2d8
> Author: felix <address@hidden>
> Date:   Sat Oct 8 15:09:42 2011 +0200
> 
>     handle EOVERFLOW and ENOTDIR gracefully in file/directory-exists?
> 
> diff --git a/runtime.c b/runtime.c
> index a6d7919..f9f8459 100644
> --- a/runtime.c
> +++ b/runtime.c
> @@ -9246,8 +9246,12 @@ C_i_file_exists_p(C_word name, C_word file, C_word dir)
>    res = stat(C_c_string(name), &buf);
>  
>    if(res != 0) {
> -    if(errno == ENOENT) return C_SCHEME_FALSE;
> -    else return C_fix(res);
> +    switch(errno) {
> +    case ENOENT: return C_SCHEME_FALSE;
> +    case EOVERFLOW: return C_truep(dir) ? C_SCHEME_FALSE : C_SCHEME_TRUE;
> +    case ENOTDIR: return C_SCHEME_FALSE;
> +    default: return C_fix(res);
> +    }
>    }
>  
>    switch(buf.st_mode & S_IFMT) {

I'm only *half* kidding when I say I would write the switch
statement like this:

switch(errno) {
case EOVERFLOW:
  if (C_truep(dir)) {
case ENOENT:
case ENOTDIR:
    return C_SCHEME_FALSE;
  } else {
    return C_SCHEME_TRUE;
  }
}

On OpenBSD, I think you'd like to handle ENAMETOOLONG by returning
C_SCHEME_FALSE too.  On that platform, EOVERFLOW is not returned
from stat.  (And I'm not sure what it is signalling, so I don't
know what this if statement is checking for.)

Will you add a check for ENAMETOOLONG?

Why is the order of errno values like it is?  If you think weaving
an if statement with a switch statement isn't me half kidding,
should they instead be in alphabetical order?

In general I think these kinds of detailed checks are a fantastic
idea, and we're going to find not every platform returns the same
errno value for a particular error condition.

-Alan
-- 
.i ma'a lo bradi cu penmi gi'e du