In order to get backtrace for firefox 36 built with default options for crash ...

  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=198384

... I tried building with DEBUG option but build fails ...

...
rm -f libdom_camera.a
/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/obj-i386-portbld-freebsd8.4/_virtualenv/bin/python /misc/work/ports/misc/ports/www/firefox/work/mozilla-release/config/expandlibs_gen.py -o libdom_came
ra.a.desc Unified_cpp_dom_camera0.o
gmake[5]: Leaving directory '/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/obj-i386-portbld-freebsd8.4/dom/camera'
gmake[5]: Entering directory '/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/obj-i386-portbld-freebsd8.4/image/build'
mkdir -p '.deps/'
nsImageModule.o
/misc/local/bin/clang++34 -o nsImageModule.o -c -I../../dist/stl_wrappers -I../../dist/system_wrappers -include /misc/work/ports/misc/ports/www/firefox/work/mozilla-release/config/gcc_hidden.h -DSTATIC_EXPORTABLE
_JS_API -DMOZILLA_INTERNAL_API -DIMPL_LIBXUL -DMOZ_GLUE_IN_PROGRAM -DAB_CD=en-US -DNO_NSPR_10_SUPPORT -I/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/image/build -I. -I/misc/work/ports/misc/ports/w
ww/firefox/work/mozilla-release/image/build/../encoders/bmp -I/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/image/build/../encoders/ico -I/misc/work/ports/misc/ports/www/firefox/work/mozilla-releas
e/image/build/../encoders/jpeg -I/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/image/build/../encoders/png -I/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/image/build/../src -I../../dist/include   -I/misc/local/include/nspr -I/misc/local/include/nss -I/misc/local/include/nss/nss -I/misc/local/include -I/misc/local/include  -I/misc/local/include/pixman-1     -fPIC  -Qunused-arguments -isystem/misc/local/include  -I/misc/local/include -DMOZILLA_CLIENT -include ../../mozilla-config.h -MD -MP -MF .deps/nsImageModule.o.pp -Qunused-arguments -isystem/misc/local/include  -I/misc/local/include -Qunused-arguments -Wall -Wempty-body -Woverloaded-virtual -Wsign-compare -Wwrite-strings -Wno-invalid-offsetof -Wno-inline-new-delete -Wno-c++0x-extensions -Wno-extended-offsetof -Wno-unknown-warning-option -Wno-return-type-c-linkage -pipe -march=prescott -g -fno-strict-aliasing -fno-exceptions -fno-strict-aliasing -fno-rtti -fno-exceptions -fno-math-errno -std=gnu++0x -pipe  -DDEBUG -DTRACING -g -O -fno-omit-frame-pointer       /misc/work/ports/misc/ports/www/firefox/work/mozilla-release/image/build/nsImageModule.cpp
In file included from /misc/work/ports/misc/ports/www/firefox/work/mozilla-release/obj-i386-portbld-freebsd8.4/dom/media/Unified_cpp_dom_media1.cpp:119:
/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/dom/media/MediaStreamGraph.cpp:1093:22: error: call to 'abs' is ambiguous
    NS_WARN_IF_FALSE(std::abs(framePosition - CurrentDriver()->StateComputedTime()) <
                     ^~~~~~~~
../../dist/include/nsDebug.h:90:11: note: expanded from macro 'NS_WARN_IF_FALSE'
    if (!(_expr)) {                                           \
          ^
/usr/include/stdlib.h:83:6: note: candidate function
int      abs(int) __pure2;
         ^
/usr/include/c++/4.2/cmath:89:3: note: candidate function
  abs(double __x)
  ^
/usr/include/c++/4.2/cmath:93:3: note: candidate function
  abs(float __x)
  ^
/usr/include/c++/4.2/cmath:97:3: note: candidate function
  abs(long double __x)
  ^
/usr/include/c++/4.2/cstdlib:143:3: note: candidate function
  abs(long __i) { return labs(__i); }
  ^
1 error generated.
/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/config/rules.mk:934: recipe for target 'Unified_cpp_dom_media1.o' failed
gmake[5]: *** [Unified_cpp_dom_media1.o] Error 1
gmake[5]: Leaving directory '/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/obj-i386-portbld-freebsd8.4/dom/media'
/misc/work/ports/misc/ports/www/firefox/work/mozilla-release/config/recurse.mk:74: recipe for target 'dom/media/target' failed
gmake[4]: *** [dom/media/target] Error 2
gmake[4]: *** Waiting for unfinished jobs....
...


ident (Ports r380244) ...

  # ident Makefile
  Makefile:
       $FreeBSD: head/www/firefox/Makefile 380090 2015-02-27 14:42:51Z jbeich $

uname ...

  # uname -a | sed -e 's/^/  /'
  FreeBSD holstein.holy.cow 8.4-STABLE FreeBSD 8.4-STABLE #4 r279514: Tue Mar  3 08:02:19 HST 2015     root@holstein.holy.cow:/misc/obj/misc/src.svn/8/sys/X200-SMP.8  i386