Re: directory caching anomalies in win32

[Aaron Shatters]

>> Date: Mon, 23 Apr 2007 16:14:47 -0700 (PDT)
>> From: Aaron Shatters <address@hidden>
>> Cc: address@hidden
>> 
>> This fragment handles the problem that inode emulation on Windows
>> >filesystems are not reliable.  It replaces the inode check by
>> >`stat'ing the directory whose normalized file name is stored in
>> >dir->path_key.
>> >
>> >Does this code really get run when you invoke $wildcard, and why?
>> 
>> Yes, it does.  "func_wildcard" calls "string_glob".  "string_glob" calls 
>> "file_exists_p".  "file_exists_p" >calls "dir_file_exists_p".  
>> "dir_file_exists_p" calls "dir_contents_file_exists_p"... and there you have 
>> >it.  The code above gets run if the $(wildcard...) argument doesn't contain 
>> any wildcard characters (for >example: file.o), and the file did not exist 
>> when the directory contents was cached.
>
>Thanks for tracing this.
>
>Paul, up until now it looks like this is a general problem with Make's
>implementation of $wildcard: it doesn't hit the disk to find out
>whether the directory got modified since it was read and cached.  I
>think that if file.o in the above example was one of the targets of
>the current Makefile, Make adds it to the cache, but what about files
>that got created as side effects of rules' commands without Make's
>knowledge?  Doesn't this mean $wildcard should always check whether
>the directory was modified?
>
>Or am I missing something?

Or, perhaps $wildcard should always check for the files existence directly, 
instead of going to the cache at all, and instead of checking directory mod 
times.  It looks like the cache isn't really designed to accomodate side effect 
files, and it also looks like changing the caching scheme would make it less 
efficient for its typical and possibly high volume use.  $wildcard seems to be 
a lower volume use, and probably isn't benefiting very much from the caching.

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