Yes, it is correct. I find that not very readable, so I suggest declaring the signature of the function to be pointed:
typedef void sigrout_t(void*);
I also have the coding convention that types ending with rout_t are such types for functions signatures. You might name it otherwise, since _t is a suffix reserved by POSIX.
Later on I am casting, perhaps to call it like
((sigrout_t*) SGENT_1_calc) (someptr);