I've been trying to get clarity on to what extent the position-independent data structure tricks in Gob (https://gist.github.com/pervognsen/c25a039fcf8c256141ef0778a1b32a88) are legal or illegal according to the C standard. I always had the impression it would run afoul of strict aliasing or pointer casting restrictions, but I've been digging into the standard, and now I'm no longer so sure. It might be perfectly legal after all?
Here's section 188.8.131.52 on pointer conversions from the C99 draft standard. I'll be referencing the C99 standard throughout this article, but I've verified that the C11 standard hasn't changed in the relevant areas.
"5 An integer may be converted to any pointer type. Except as previously specified, the result is implementation-defined, might not be correctly aligned, might not point to an entity of the referenced type, and might be a trap representation. 
6 Any pointer type may be converted to an integer type. Except as previously specified, the result is implementation-defined