Compiling JDK 8 head with --with-extra-ldflags="-Wl,-z,defs" results in a build failure in when linking the SA debugger backend:

Making SA debugger back-end...
/usr/bin/gcc -Damd64 -D_GNU_SOURCE \
-D_FILE_OFFSET_BITS=64 \
                   -g -m64 -shared -fPIC \
           -I/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux \
           -I../generated \
           -I/usr/lib/jvm/java-1.8.0-openjdk/include \
           -I/usr/lib/jvm/java-1.8.0-openjdk/include/linux \
\
           /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/salibelf.c /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/symtab.c /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/libproc_impl.c /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/ps_proc.c /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/ps_core.c /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/LinuxDebuggerLocal.c /disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/share/native/sadis.c \
           -Xlinker --version-script=/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/os/linux/mapfile -Wl,--hash-style=both "-Wl,-z,noexecstack" -Wl,-z,defs \
           -g \
           -DJDWP_LOGGING -std=gnu++98 \
           -o libsaproc.so \
           -lthread_db
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
cc1: warning: command line option ‘-std=gnu++98’ is valid for C++/ObjC++ but not for C
/tmp/ccJ2XvnU.o: In function `Java_sun_jvm_hotspot_asm_Disassembler_load_1library':
/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/share/native/sadis.c:138: undefined reference to `dlopen'
/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/share/native/sadis.c:141: undefined reference to `dlopen'
/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/share/native/sadis.c:144: undefined reference to `dlsym'
/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/agent/src/share/native/sadis.c:147: undefined reference to `dlerror'
collect2: error: ld returned 1 exit status
gmake[6]: *** [/disk/openjdk/upstream-sources/openjdk8u-dev/hotspot/make/linux/makefiles/saproc.make:85: libsaproc.so] Error 1
gmake[6]: *** Waiting for unfinished jobs....

This isn't an issue on latest JDK (12) or any JDK with the new build system JDK 9+. Hence, JDK 8 only.