Bug 2336442

bigloo-4.5b/autoconf/stacksize
has
int (*fun)();
int glob;

int foo( int x, int y ) {
  return x * y;
}
      
int bar( int x, int y ) {
  return x + y;
}

int ssize( int size ) {
   glob++;
   
   if( size == 0 )
      return 0;
   else
      return fun( size, ssize( size - 1 ) );
}

int main( int argc, char *argv[] ) {
   fun = argc > 2 ? &bar : &foo;

   if( ssize( $stacksize * 1024 * 32 ) >= 0 )
      return 0;
   else
      return argc-1;
}
in it.  This used to be valid in C17, but is not valid in C23, where int (*fun)(); doesn't mean function pointer with unspecified parameters, but it means the same thing as int (*fun)(void); (like in C++).
I think
--- bigloo-4.5b/autoconf/stacksize	2023-12-22 17:18:46.000000000 +0100
+++ bigloo-4.5b/autoconf/stacksize	2025-01-09 16:46:01.346136400 +0100
@@ -58,7 +58,7 @@ rm -f $aout.exe 2> /dev/null
 #*    Test                                                             */
 #*---------------------------------------------------------------------*/
 cat > $file.c <<EOF
-int (*fun)();
+int (*fun)( int, int );
 int glob;
 
 int foo( int x, int y ) {
should fix this, but haven't tried it...

Indeed, that works.  Thank you, Jakub!  A similar fix is also needed for autoconf/dlopen.  And then there are more instances of empty parameter lists in the code itself.  I think I'm going to have to build bigloo in C17 mode for now until I have time to fix up the sources.

Closing, since bigloo did build successfully during the F42 mass rebuild.  I will talk to upstream about updating the sources for C23.