From: Jan Engelhardt <ej@inai.de>
Date: 2025-06-22 22:59:12.725516319 +0200

gcc-15 for some reason stumbles over itself. If it had not ignored noreturn,
there would be no reaching of end-of-function.
Add a filler return statement.

[   23s] nauty.h:1467:1: warning: 'noreturn' attribute ignored [-Wattributes]
[   23s]  1467 | extern void NORET_ATTR alloc_error(const char*);
[   23s] gtnauty.c: In function 'findarc':
[   23s] gtnauty.c:942:1: error: control reaches end of non-void function [-Werror=return-type]

---
 gtnauty.c |    1 +
 1 file changed, 1 insertion(+)

Index: nauty2_8_9/gtnauty.c
===================================================================
--- nauty2_8_9.orig/gtnauty.c
+++ nauty2_8_9/gtnauty.c
@@ -939,6 +939,7 @@ findarc(arc *a, int na, int from, int to
             lo = mid + 1;
     }
     gt_abort(">E findarc error\n");
+    return 0;
 }
 
 void