The PVFS2 source is heavily dependent on a state machine implementation that is included in the tree. We've already noted that the parser, statecomp, is located in the src/common/statecomp subdirectory. Additional code for processing state machines is in src/common/misc.
State machine source is denoted with a .sm suffix. These are converted to .c files by statecomp. If you are building out of tree, the .c files will end up in the build tree; otherwise you'll be in the confusing situation of having both versions in the same subdirectory. If modifying these, be careful to only modify the .sm files – the corresponding .c file can be overwritten on rebuilds.