TYPO3 Core

I had a look at this issue and figured out the following:

1. The error happens when somehow :D an empty session file is generated in "typo3temp/var/InstallToolSessions/<sessionFolder>/hash_<sessionName>

I would say a fix should be to check if result of filesize is not 0 and not false:

$length = filesize($sessionFile);
if(!empty($length)) {
   $content = fread($fd, $length);
}

What i currently don't understand, how this could happen. One possible reason is that for example the write method is
interrupted between "ftruncate" and "fwrite" which would result in a left empty file. If you force this by terminating the write process randomly at that point you have the desrcibed problem. Once an empty session file is there you continuesly have this error message in the install tool. By now i did not find another way to reproduce this.

Another way to force the error is to just truncate the file on the filesystem.

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/51835

Patch set 3 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/51835