Actually crashes as follows, minimal reproducer via `jsc':

$ /usr/pkg/libexec/webkit2gtk-4.0/jsc
Segmentation fault (core dumped)

...and, if compiled with CFLAGS=-g, and just running jsc inside the work
directory:

$ env LD_LIBRARY_PATH=./lib gdb -core jsc.core bin/jsc
[...]
Reading symbols from bin/jsc...
[New process 6829]
[New process 29521]
Core was generated by `jsc'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  JSC::MarkedBlock::Footer::Footer (handle=..., vm=..., this=0x7aadc0007ed0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/MarkedBlock.cpp:97
97      MarkedBlock::Footer::Footer(VM& vm, Handle& handle)
[Current thread is 1 (process 6829)]
(gdb) bt
#0  JSC::MarkedBlock::Footer::Footer (handle=..., vm=..., this=0x7aadc0007ed0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/MarkedBlock.cpp:97
#1  JSC::MarkedBlock::MarkedBlock (handle=..., vm=..., this=0x7aadc0004000) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/MarkedBlock.cpp:87
#2  JSC::MarkedBlock::Handle::Handle (this=0x7aae178d0000, heap=..., alignedMemoryAllocator=0x7aae178ec9b0, blockSpace=0x7aadc0004000) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/MarkedBlock.cpp:66
#3  0x00007aae1ed8590b in JSC::MarkedBlock::tryCreate (heap=..., alignedMemoryAllocator=0x7aae178ec9b0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/MarkedBlock.cpp:59
#4  0x00007aae1ed5842a in JSC::BlockDirectory::tryAllocateBlock (this=0x7aae17608560, heap=...) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/BlockDirectory.cpp:117
#5  0x00007aae1ed8221e in JSC::LocalAllocator::allocateSlowCase (this=this@entry=0x7aae176099d0, heap=..., deferralContext=deferralContext@entry=0x0, failureMode=failureMode@entry=JSC::AllocationFailureMode::Assert) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/LocalAllocator.cpp:145
#6  0x00007aae1f873acc in JSC::LocalAllocator::allocate(JSC::Heap&, JSC::GCDeferralContext*, JSC::AllocationFailureMode)::{lambda()#1}::operator()() const (__closure=<optimized out>) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/LocalAllocatorInlines.h:41
#7  JSC::FreeList::allocate<JSC::LocalAllocator::allocate(JSC::Heap&, JSC::GCDeferralContext*, JSC::AllocationFailureMode)::{lambda()#1}>(JSC::LocalAllocator::allocate(JSC::Heap&, JSC::GCDeferralContext*, JSC::AllocationFailureMode)::{lambda()#1} const&) (slowPath=..., this=0x7aae176099e8) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/FreeListInlines.h:46
#8  JSC::LocalAllocator::allocate (failureMode=JSC::AllocationFailureMode::Assert, deferralContext=0x0, heap=..., this=0x7aae176099d0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/LocalAllocatorInlines.h:38
#9  JSC::Allocator::allocate (mode=JSC::AllocationFailureMode::Assert, context=0x0, heap=..., this=<synthetic pointer>) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/AllocatorInlines.h:35
#10 JSC::GCClient::IsoSubspace::allocate (failureMode=JSC::AllocationFailureMode::Assert, deferralContext=0x0, size=size@entry=112, vm=..., this=0x7aae176099d0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/heap/IsoSubspaceInlines.h:36
#11 JSC::tryAllocateCellHelper<JSC::Structure> (failureMode=JSC::AllocationFailureMode::Assert, deferralContext=0x0, size=size@entry=112, heap=...) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/runtime/JSCellInlines.h:181
#12 JSC::allocateCell<JSC::Structure> (vm=..., size=size@entry=112) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/runtime/JSCellInlines.h:195
#13 0x00007aae1f1bc32e in JSC::Structure::createStructure (vm=...) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/runtime/StructureInlines.h:72
#14 JSC::VM::VM (this=0x7aae17600000, vmType=<optimized out>, heapType=<optimized out>, runLoop=<optimized out>, success=0x0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/runtime/VM.cpp:254
#15 0x00007aae1f1bece4 in JSC::VM::create (heapType=heapType@entry=JSC::HeapType::Large, runLoop=runLoop@entry=0x0) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/runtime/VM.cpp:520
#16 0x000000008d4190e6 in runJSC<jscmain(int, char**)::<lambda(JSC::VM&, GlobalObject*, bool&)> >(const struct {...} &, bool, const CommandLine &) (func=..., isWorker=false, options=...) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/jsc.cpp:3607
#17 0x000000008d41aafb in jscmain (argc=argc@entry=1, argv=argv@entry=0x7f7fffa92d98) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/jsc.cpp:3794
#18 0x000000008d41bbf1 in main (argc=1, argv=0x7f7fffa92d98) at /tmp/pkgsrc/wip/webkit-gtk/work/webkitgtk-2.36.1/Source/JavaScriptCore/jsc.cpp:3020
