Hi,
I don't know who generates the c99.tags, but it would be cool if the next release of Geany had the `size_t` symbol in its default tags. I can't get Geany to parse my GNU headers using create_c_tags.sh script (or otherwise), but even just copying the line for `ssize_t` and dropping the first S works well enough to get auto-completion and highlighting of this symbol.
Cheers, Matthew Brush