ASAN and slowdebug

[Stuart Monteith]

Hello,
   While looking at ASAN to try to reproduce another issue with ASAN, I tried building OpenJDK configured with:
       --enable-asan --with-debug-level=slowdebug

However, there is a compilation problem that persists up to and include GCC 12.2.0:
	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80959

As slowdebug builds are built with -O0, this results in code to be inserted by the macros LEAVE() and CHECK_NH+CHECK_ 
macros to be not optimised away. This causes the following two warnings/errors:

  * For target hotspot_variant-server_libjvm_objs_memoryService.o:
jdk/src/hotspot/share/services/memoryService.cpp: In static member function 'static Handle 
MemoryService::create_MemoryUsage_obj(MemoryUsage, JavaThread*)':
jdk/src/hotspot/share/services/memoryService.cpp:219:1: error: control reaches end of non-void function 
[-Werror=return-type]

  * For target support_native_java.base_libjli_java.o:
jdk/src/java.base/share/native/libjli/java.c: In function 'JavaMain':
jdk/src/java.base/share/native/libjli/java.c:556:1: error: control reaches end of non-void function [-Werror=return-type]
   556 | }
       | ^


There are a couple of ways of working around this. One is to  change create_MemoryUsage_obj and libjli/java.c to place a 
return statement at the end of the function block, after the macros. The changes are straightforward, but we're 
obviously not guaranteed to not reintroduce the problem elsewhere.

Another is to pass:  "--disable-warnings-as-errors" or more specifically "--with-extra-cflags=-Wno-return-type 
--with-extra-cxxflags=-Wno-return-type" to configure. This would be a manual process, unless the make files were changed 
to handle this, however this does remove the return type checks.


Part of the reason for sending this is to at least document the issue publicly. Are there any opinions on what should to 
be done next?


Stuart