I'm getting many copies of this build warning, when doing a debug build of up-to-date mozilla-inbound w/ gcc 4.7.2 on Ubuntu 12.10: { 0:54.94 In file included from /scratch/work/builds/mozilla-inbound/mozilla/js/src/jsscope.h:14:0, 0:54.94 from /scratch/work/builds/mozilla-inbound/mozilla/js/src/jsscript.h:16, 0:54.94 from /scratch/work/builds/mozilla-inbound/mozilla/js/src/vm/SPSProfiler.h:18, 0:54.94 from /scratch/work/builds/mozilla-inbound/mozilla/js/src/jscntxt.h:36, 0:54.94 from /scratch/work/builds/mozilla-inbound/mozilla/js/src/jsarray.h:12, 0:54.94 from /scratch/work/builds/mozilla-inbound/mozilla/js/src/jsfun.cpp:19: 0:54.94 Warning: enabled by default in /scratch/work/builds/mozilla-inbound/mozilla/js/src/jsobj.h: inline function 'js::Module& JSObject::asModule()' used but never defined 0:54.94 /scratch/work/builds/mozilla-inbound/mozilla/js/src/jsobj.h:1037:24: warning: inline function 'js::Module& JSObject::asModule()' used but never defined [enabled by default] } I'm attaching a snippet of my clobber build output that includes all of these build warnings for various .cpp files that include jsobj.h and spam about this. I believe this function declaration "asModule()" was added in bug 568953 -- I originally posted about this over there, but I'm spinning this off as a separate bug so as not to clutter up that bug too much.

Bug 568953 was merged over to m-c, so this affects m-c builds now, too. Sample build log: { sclone.cpp ../../../js/src/jsobj.h:1037:24: warning: inline function 'js::Module& JSObject::asModule()' used but never defined /usr/bin/ccache /tools/gcc-4.5-0moz3/bin/g++ -o jsclone.o -c -I./../../dist/system_wrappers_js -include /builds/slave/m-cen-lnx-dbg/build/js/src/config/gcc_hidden.h -DENABLE_TYPEDARRAY_MOVE -DENABLE_YARR_JIT=1 -DMOZ_GLUE_IN_PROGRAM -DNO_NSPR_10_SUPPORT -DEXPORT_JS_API -DJS_HAS_CTYPES -DDLL_PREFIX=\"lib\" -DDLL_SUFFIX=\".so\" -DUSE_ZLIB -Ictypes/libffi/include -I. -I/builds/slave/m-cen-lnx-dbg/build/js/src/../../mfbt/double-conversion -I/builds/slave/m-cen-lnx-dbg/build/js/src -I. -I./../../dist/include -I/builds/slave/m-cen-lnx-dbg/build/obj-firefox/dist/include/nspr -I/builds/slave/m-cen-lnx-dbg/build/js/src -I/builds/slave/m-cen-lnx-dbg/build/js/src/assembler -I/builds/slave/m-cen-lnx-dbg/build/js/src/yarr -fPIC -pedantic -Wall -Wpointer-arith -Woverloaded-virtual -Werror=return-type -Wtype-limits -Wempty-body -Werror=conversion-null -Wno-ctor-dtor-privacy -Wno-overlength-strings -Wno-invalid-offsetof -Wno-variadic-macros -Wcast-align -Wno-long-long -fno-rtti -ffunction-sections -fdata-sections -fno-exceptions -pthread -pipe -DDEBUG -D_DEBUG -DTRACING -g -O3 -freorder-blocks -finline-limit=50 -fno-omit-frame-pointer -DUSE_SYSTEM_MALLOC=1 -DENABLE_ASSEMBLER=1 -DENABLE_JIT=1 -DMOZILLA_CLIENT -include ./js-confdefs.h -MD -MF .deps/jsclone.o.pp /builds/slave/m-cen-lnx-dbg/build/js/src/jsclone.cpp jscntxt.cpp ../../../js/src/jsobj.h:1037:24: warning: inline function 'js::Module& JSObject::asModule()' used but never defined } ...(and more) https://tbpl.mozilla.org/php/getParsedLog.php?id=18971882&tree=Firefox

(Looks like Edddy's got a fix for this over on bug 568953. woot)

Fixed by bug 568953 comment 45. (which was merged to m-c 3 comments later)