TYPO3 Core

This is the code:
t3lib_div::writeFile($mfile, $mirrorsFile);
$mirrors = implode(gzfile($mfile));
t3lib_div::unlink_tempfile($mfile);

I cannot see immediately when this leaves a file behind. Do you have any further information?

No. I found this when allow_url_fopen was off and curl was disabled. I got new mirror* file each time. Here is a partial content of this folder with permissions:

beauty:~ # ls -al /srv/www/web1/web/typo3temp
total 1310
drwxrwxr-x    8 root   apache   2640 Apr  3 08:52 .
drwxrwxr-x   13 root   web1      752 Apr  2 18:57 ..
drwxrwxr-x    2 root   apache    240 Apr  2 16:10 GB
drwxr-xr-x  250 apache apache   6000 Apr  2 14:41 cache_pages
drwxr-xr-x    2 apache apache    200 Apr  2 15:23 cs
-rw-r--r--    1 apache apache 497699 Apr  3 08:49 extensions.bin
-rw-r--r--    1 apache apache 485533 Apr  3 08:49 extensions.xml.gz
drwxr-xr-x    2 apache apache  16008 Apr  3 08:52 llxml
-rw-------    1 apache apache      0 Apr  2 22:41 mirrors3NsEt0
-rw-------    1 apache apache      0 Apr  2 22:32 mirrors3j9s04
-rw-------    1 apache apache      0 Apr  2 22:42 mirrors3s3oxM
-rw-------    1 apache apache      0 Apr  2 22:48 mirrors3wdsD7
-rw-------    1 apache apache      0 Apr  2 22:30 mirrorsC5qPlj
-rw-------    1 apache apache      0 Apr  2 22:48 mirrorsO5tu8x
-rw-------    1 apache apache      0 Apr  2 22:30 mirrorsaAy8YN
-rw-------    1 apache apache      0 Apr  2 22:31 mirrorscePRxO
-rw-------    1 apache apache      0 Apr  2 22:31 mirrorsd3m2lv
-rw-------    1 apache apache      0 Apr  2 22:31 mirrorslwPhUN
-rw-------    1 apache apache      0 Apr  2 22:42 mirrorspud6CP
-rw-------    1 apache apache      0 Apr  2 22:40 mirrorsscxeDU
-rw-------    1 apache apache      0 Apr  2 22:31 mirrorssjwb0D
drwxr-xr-x    2 apache apache   1456 Apr  3 06:47 pics

Ah, one never stops learning. tempnam not only returns a filename, but actually creates the file. So I needed to add another unlink call. See attached patch (which adds clearer error messages, too).

I would only change "allow_url_fopen not allowed, curl not enabled" to "allow_url_fopen is off, curl is not enabled in Install tool". Otherwise looks great! :)

The suggested change will be put into the patch.