dedupe-02.js - mozsearch

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// AutoStableStringChars needs to prevent the owner of its chars from being

// deduplicated, even if they are held by a different string.

gczeal(0);

function makeExtensibleStrFrom(str) {

  var left = str.substr(0, str.length/2);

  var right = str.substr(str.length/2, str.length);

  var ropeStr = left + right;

  return ensureLinearString(ropeStr);

// Make a string to deduplicate to.

var original = makeExtensibleStrFrom('{ "phbbbbbbbbbbbbbbttt!!!!??": [1] }\n\n');

// Construct D2 -> D1 -> base

var D2 = makeExtensibleStrFrom('{ "phbbbbbbbbbbbbbbttt!!!!??": [1] }');

var D1 = newRope(D2, '\n', {nursery: true});

ensureLinearString(D1);

var base = newRope(D1, '\n', {nursery: true});

ensureLinearString(base);

// Make an AutoStableStringChars(D2) and do a minor GC within it. (This will do

// a major GC, but it'll start out with a minor GC.) `base` would get

// deduplicated to `original`, if it weren't for AutoStableStringChars marking

// all of D2, D1, and base non-deduplicatable.

// The first time JSON.parse runs, it will create several (14 in my test) GC

// things before getting to the point where it does an allocation while holding

// the chars pointer. Get them out of the way now.

JSON.parse(D2);

// Cause a minor GC to happen during JSON.parse after AutoStableStringChars

// gives up its pointer.

schedulegc(1);

JSON.parse(D2);

// Access `D2` to verify that it is not using the deduplicated chars.

print(D2);