Archiv der Kategorie: Computing

Troubles with GCC signed integer overflow optimization

As signed integer wraparound (overflow) is not defined by C/C++ standards, GCC sometimes optimizes expressions with the assumption that wraparound does not happen, even though the CPU very well does perform wraparound. This can lead to cases in which the … Weiterlesen

Veröffentlicht unter Computing | Verschlagwortet mit , , , , | 1 Kommentar

GCC strict aliasing pitfall

In some cases of badly written C/C++ code, the behaviour of a program may depend on the optimization level that was used to compile the code because GCC applies strict aliasing optimizations when compiling with -O2 or higher. According to … Weiterlesen

Veröffentlicht unter Computing | Verschlagwortet mit , , , , | 2 Kommentare

apt-show-versions: magic number checking on storable file failed

I’m posting this in the hope that it might be helpful for somebody, sometime: I’ve been annoyed by the following error of apt-show-versions, recently: Magic number checking on storable file failed at ../../lib/Storable.pm (autosplit into ../../lib/auto/Storable/_retrieve.al) line 331, at /usr/bin/apt-show-versions … Weiterlesen

Veröffentlicht unter Computing | Verschlagwortet mit , | Hinterlasse einen Kommentar

Preventing brute force attacks using iptables recent matching

General idea In recent times our network has seen a lot of attempts to brute-force ssh passwords. A method to hamper such attacks by blocking attacker’s IP addresses using iptables ‘recent’ matching is presented in this text: When the amount … Weiterlesen

Veröffentlicht unter Computing | Verschlagwortet mit , , , , , | 3 Kommentare