This was ultimately my error but clearer error handling could have saved me an hour or two.

While working on https://bugs.openjdk.org/browse/JDK-8292561, I tried to make ReplayCompiles a product (diagnostic) switch. Depending on ReplayCompiles, however, we set UseDebuggerErgo. UseDebuggerErgo is a notproduct switch.

So I found that setting a notproduct switch in a product build just crashes. And if that happens before os_init in early arg parsing, we won't even have a signal handler in place, so no hs-err file, just "Segmentation Fault".

You just cannot run a debug VM here to see assert since the error depends on the VM being product. Therefore, a guarantee somewhere would be helpful.

Here's a reproducer:

=====================
diff src/hotspot/share/gc/shared/gcConfig.cpp

 void GCConfig::select_gc_ergonomically() {
+ FLAG_SET_ERGO(CheckCompressedOops, true);
   if (os::is_server_class_machine()) {
=====================

# The VM exits with no apparent error message

$ java -version; echo $?
139