Comment # 2 on bug 1224533 from Reinhard Max

Ah, the check makes use of implicit int which is now also an error and lets the
check for (void *) fail leading to the assumption that (char *) is needed for
qsort():

configure:23571: checking argument pointer type of qsort compare function and
base
configure:23600: gcc -c [...] conftest.c
conftest.c:141:8: error: type defaults to 'int' in declaration of 'sortf'
[-Wimplicit-int]
  141 | extern sortf(const void *, const void *);
      |        ^~~~~
[...]
configure: failed program was:
[...]
| extern void *base;
| extern sortf(const void *, const void *);
| int sortf(a, b)
|   const void *a;
|   const void *b; { return 0; }
[...]
configure:23611: result: char