Bug 213593

Summary: JSCell constructor needs to ensure that the passed in structure is still alive.
Product: WebKit Reporter: Mark Lam <mark.lam>
Component: JavaScriptCoreAssignee: Mark Lam <mark.lam>
Status: RESOLVED FIXED    
Severity: Normal CC: ews-watchlist, keith_miller, msaboff, saam, tzagallo, webkit-bug-importer, ysuzuki
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
proposed patch.
ysuzuki: review+
patch for landing. none

Mark Lam
Reported 2020-06-25 00:52:13 PDT
<rdar://problem/64597573>
Attachments
proposed patch. (3.96 KB, patch)
2020-06-25 01:14 PDT, Mark Lam 		ysuzuki: review+
DetailsFormatted DiffDiff
patch for landing. (5.25 KB, patch)
2020-06-25 12:14 PDT, Mark Lam 		no flags
DetailsFormatted DiffDiff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.
Mark Lam
Comment 1 2020-06-25 01:14:25 PDT
Created attachment 402722 [details] proposed patch.
Yusuke Suzuki
Comment 2 2020-06-25 08:50:55 PDT
Comment on attachment 402722 [details] proposed patch. r=me
Mark Lam
Comment 3 2020-06-25 12:03:26 PDT
Offline, Keith and Yusuke questions why Clang would have precomputed Structure field values. Turns out, Clang did not pre-compute the field values. Instead, it pre-computed the address of structure->m_blob where all the field values are contained. As a result, the structure pointer is no longer retained, and GC will not know to keep the structure alive. The fix is still valid. I'll update the comment to indicate that it is the address of structure->m_blob that is pre-computed.
Mark Lam
Comment 4 2020-06-25 12:14:51 PDT
Created attachment 402787 [details] patch for landing.
Mark Lam
Comment 5 2020-06-25 12:33:40 PDT
Thanks for the review. Landed in r263523: <http://trac.webkit.org/r263523>.
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