c - Get struct's size passed as void to function -

i'm changing codes in database library. way works send void pointer, size of call query , using query calculate size of structure. problem receive struct params function fails before/in middle of first fetch. after need clear structure, dont have size. know best way send size of structure param, have thousands , thousands programs compiled, library 1996, need find way calculate structure size if type void.

one idea had calculate position of next element not in structure

0x000010              0x000042 [int|char[30]|int|int][int] 

so size 32, because 0x00042-0x000010 32.

is there way know when got out of structure.

the prototype of function is

int getdata(char* fields, void* mystruct) 

i need find out structure size.

sorry if missed information, code huge , unfortunately cannot post here.

no, in general there's no way, given void *, figure out you're after. thing can compare against null, of course doesn't here.

note there's nothing in void * says points @ struct, pointing middle of array.

if have global means of recording pointers before they're passed getdata(), might able implement look-up function compares pointer value against recorded, that's using pointer value key.