DirEntries() fails on symbolic links to non-existent file

[dlangBugzillaToGithub]

ckatko reported this on 2019-08-05T23:52:22Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=20109

CC List

• shove

Description

DirEntries() fails on symbolic links to non-existent file. I just had this bug show up.

 - I'm making a program that scans all the files in a path and computes their hashes. DirEntries keeps exploding on a random symlink on my hard drive.

 - I passed "false" to "followSymlink" in DirEntries(), but it still fails regardless and throws an exception. 

 - The reason I believe, is that this random spurious file (cmt_drv.la) I have is a symlink to "../cmt_drv.la", and that file doesn't exist. 

output:
-----

commandline args:
0 ./dup
1 /home/novous/Downloads/DOWNLOADS BUFFER/xf86-input-cmt/src/.libs/

object.Exception@std/file.d(3219): Failed to stat file `/home/novous/Downloads/DOWNLOADS BUFFER/xf86-input-cmt/src/.libs/cmt_drv.la'
----------------
??:? pure @safe void std.exception.bailOut!(Exception).bailOut(immutable(char)[], ulong, const(char[])) [0x6cdb691e]
??:? pure @safe bool std.exception.enforce!(Exception, bool).enforce(bool, lazy const(char)[], immutable(char)[], ulong) [0x6cd9f9e1]
??:? @trusted void std.file.DirEntry._ensureStatDone() [0x6cd772ee]
??:? @property @safe ulong std.file.DirEntry.size() [0x6cd7713c]
??:? _Dmain [0x6cd58c81]

on github here:

https://github.com/dlang/phobos/blob/master/std/file.d#L3979

It appears "stat" is failing.

This might be key: I'm trying to run sort!("a.size > b.size") on the returned DirEntries, and while sorting it calls .size() which then invokes the stat command.

This program works fine until I ran into this edge-case. I can provide code snippets and clarification as needed. 

Thanks,
--Chris

[dlangBugzillaToGithub]

shove commented on 2019-08-06T06:11:15Z

I don't think there is any problem here. It is correct to throw an exception to a non-existent file getSize.

When traversing files, folders and symlinks, we should judge them and decide whether to do some operations.


    import std.file;
    import std.stdio;

    string path = "...";
    foreach (DirEntry e; dirEntries(path, SpanMode.shallow))
    {
        if (e.isSymlink)
        {
            string origin = readLink(e.name);
            if (origin.exists)
                writeln(origin, ", size: ", e.size);
            else
                writeln(origin, " not exists. ");
        }
    }