Use __builtin_unreachable(). [skip ci]

Refine the changes made in commit 3f35396 and use a macro with comments.

1 files changed, 16 insertions, 0 deletions

diff --git a/diag-control.h b/diag-control.h
index c1ec5acd..d1622aa6 100644
--- a/diag-control.h
+++ b/diag-control.h
@@ -316,4 +316,20 @@
   #endif
 #endif
 
+/*
+ * GCC needs this on AIX for longjmp().
+ */
+#if PCAP_IS_AT_LEAST_GNUC_VERSION(5,1)
+  /*
+   * Beware that the effect of this builtin is more than just squelching the
+   * warning! GCC trusts it enough for the process to segfault if the control
+   * flow reaches the builtin (an infinite empty loop in the same context would
+   * squelch the warning and ruin the process too, albeit in a different way).
+   * So please remember to use this very carefully.
+   */
+  #define PCAP_UNREACHABLE __builtin_unreachable();
+#else
+  #define PCAP_UNREACHABLE
+#endif
+
 #endif /* _diag_control_h */