I encountered a strange problem. While saving a graph from a script, the generated file is mostly )or completely) composed by "NUL" characters. This happens with both dot and xml.gz outputs.
The script correclty prints the number of edges and vertices. The properties list is also correct and the labels of the vertices are correctly stored in memory andd printed on screen.
The only output to the file is a huge number of NUL and, in the dot case, some of the edges.
The error happens after building the graph from a data file (with a custom script) and also after loading (in the interactive console) graphs previously saved in xml.gz format with graph_tool.
I cannot reproduce the error via interactive console creating a graph with 2 nodes, 1 edge and no properties.

OS is ubuntu and graph_tool version is 2.2.15-1

Everything worked just fine until past week.

Thanks in advance for the help,