1.0.0-alpha.2 JavaScript heap out of memory

[jimmont]

reverting to 0.4.5 fixed the following issue in that it doesn't exhaust the heap or masks this and exits.
if I find more details plan to share them here.
it's unclear what in our independent project (not istanbul) is the source of the problem.

uname -a
Darwin  17.7.0 Darwin Kernel Version 17.7.0: Thu Jun 21 22:53:14 PDT 2018; root:xnu-4570.71.2~1/RELEASE_X86_64 x86_64
node -v
v8.11.4
npm -v
6.4.0
"istanbul": "^1.0.0-alpha.2",

problem:
<--- Last few GCs --->

[25457:0x102806a00]   971082 ms: Mark-sweep 1330.4 (1480.9) -> 1330.0 (1488.4) MB, 1026.0 / 0.0 ms  allocation failure GC in old space requested
[25457:0x102806a00]   972117 ms: Mark-sweep 1330.0 (1488.4) -> 1330.0 (1449.9) MB, 1034.5 / 0.0 ms  last resort GC in old space requested
[25457:0x102806a00]   973220 ms: Mark-sweep 1330.0 (1449.9) -> 1330.0 (1446.9) MB, 1103.2 / 0.0 ms  last resort GC in old space requested


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x14707e725879 <JSObject>
    1: update [crypto.js:~97] [pc=0x901d8ee9223](this=0x1470eacfd829 <Hash map = 0x14701ab7cac1>,data=0x14703b7385b9 <Very long string[3617303]>,encoding=0x1470341022d1 <undefined>)
    2: arguments adaptor frame: 1->2
    3: exit [/projects/node_modules/istanbul-lib-instrument/dist/visitor.js:575] [bytecode=0x1470070690e1 offset=202](this=0x1470989840f9 <Object map ...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
 1: node::Abort() [/.nvm/versions/node/v8.11.4/bin/node]
 2: node::FatalException(v8::Isolate*, v8::Local<v8::Value>, v8::Local<v8::Message>) [/.nvm/versions/node/v8.11.4/bin/node]
 3: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [/.nvm/versions/node/v8.11.4/bin/node]
 4: v8::internal::Factory::NewRawTwoByteString(int, v8::internal::PretenureFlag) [/.nvm/versions/node/v8.11.4/bin/node]
 5: v8::internal::String::SlowFlatten(v8::internal::Handle<v8::internal::ConsString>, v8::internal::PretenureFlag) [/.nvm/versions/node/v8.11.4/bin/node]
 6: v8::String::WriteUtf8(char*, int, int*, int) const [/.nvm/versions/node/v8.11.4/bin/node]
 7: node::StringBytes::Write(v8::Isolate*, char*, unsigned long, v8::Local<v8::Value>, node::encoding, int*) [/.nvm/versions/node/v8.11.4/bin/node]
 8: node::crypto::Hash::HashUpdate(v8::FunctionCallbackInfo<v8::Value> const&) [/.nvm/versions/node/v8.11.4/bin/node]
 9: 0x901d8cd0f67
10: 0x901d8ee9223