c - Using function returning pointer as lvalue -

say want dynamically allocate array can hold data, i.e. using void** type, in c. then, rather re-writing pointer arithmetic logic each time, want simple function returns address of element. why cannot use function in assignment (i.e., can set, element's value)?

here's example code:

#include <stdio.h> #include <stdlib.h>  void printintarray(void** array, size_t length) {   printf("array @ %p\n", array);   while (length--) {     printf("  [%zu] @ %p -> %p", length, array + length, *(array + length));     if (*(array + length)) {       printf(" -> %d", *(int*)*(array + length));     }     printf("\n");   } }  void* getelement(void** array, size_t index) {   return *(array + index); }  int main(int argc, char** argv) {   const size_t n = 5;   size_t i;    /* n element array */   void** test = malloc(sizeof(void*) * n);   = n;   while (i--) {     *(test + i) = null;   }    /* set element [1] */   int testdata = 123;   printf("testdata @ %p -> %d\n", &testdata, testdata);   *(test + 1) = (void*)&testdata;    printintarray(test, n);    /* prints 123, expected */   printf("array[1] = %d\n", *(int*)getelement(test, 1));    /* new in [2] */   /* fixme  lvalue required left operand of assignment */   int testthing = 456;   getelement(test, 2) = (void*)&testthing;   printintarray(test, n);    return 0; } 

it wouldn't fist time question has been asked, answer along lines of "you trying assign function, rather return value of function, not allowed". fair enough, can 1 around this? i'm confused!!

implement getelement() this:

void ** getelement(void ** ppv, size_t index) {   return ppv + index; } 

and use this:

 *getelement(test, 2) = &testthing; 

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if you'd use macro go way intended:

#define get_element(ppv, index) \   (*(ppv + index)) 

use this:

get_element(test, 2) = &testthing;