"Conflicting types" build failure(s) — clang 9.0.1

clang considers conflicting declarations as error while gcc just shows a warning
// clang  -c  foo.c
#include <stdio.h>
char *getline(int fd) { return NULL; }
PackageVersionSupposed error messageFull log Bug report
cinnamon-settings-daemon 4.4.0-3csd-xrandr-manager.c:2304:1: error: conflicting types for 'register_manager_dbus' Log
freefem 3.5.8-7setjmp.h:54:12: error: conflicting types for '__sigsetjmp' Log
jackeq 0.5.9-3main.c:251:6: error: conflicting types for 'getSettings' Log 753432
k2pdfopt 2.51+ds-1ocrtess.c:70:6: error: conflicting types for 'ocrtess_lang_default' Log
opensmtpd-extras 6.6.0-1stdio.h:354:12: error: conflicting types for 'snprintf' Log
pccts 1.33MR33-6genmk.c:971:1: error: conflicting types for 'pclasses' Log 753538

6 errors