https://bugs.gentoo.org/898084
https://bugs.gentoo.org/932312
nothing defined HAVE_STDLIB_H to permit inclusion of stdlib.h,
which caused failures to find correct version of db
also fill the function definitions for C23
--- a/configure.ac
+++ b/configure.ac
@@ -5,6 +5,9 @@
 AC_INIT(src/main.c.in)
 AC_CONFIG_HEADER(src/config.h)
 
+AC_INCLUDES_DEFAULT
+AC_USE_SYSTEM_EXTENSIONS
+
 dnl
 dnl Checks for programs.
 dnl
--- a/src/sg.h.in
+++ b/src/sg.h.in
@@ -360,7 +360,7 @@
 void   sgEmergency __P(());
 void   sgReloadConfig __P(());
 void   sgHandlerSigHUP __P((int));
-void   sgAlarm __P(());
+void   sgAlarm __P((int signal));
 int    sgStrRcmp __P((char *, char *));
 int    sgStrRncmp __P((char *, char *, int));
 int    sgDomStrRncmp __P((char *, char *, int));
@@ -431,7 +431,7 @@
 int    sgRegExpMatch __P((struct sgRegExp *, char *));
 char   *sgRegExpSubst __P((struct sgRegExp *, char *));
 
-void   sgDbInit __P(());
+void   sgDbInit __P((struct sgDb *Db, char *file));
 void   sgDbLoadTextFile __P((struct sgDb *, char *, int));
 void   sgDbUpdate __P((struct sgDb *, char *, char *, size_t));