62006 - assertions about static ctors

Status: RESOLVED WORKSFORME

(Core :: XPCOM, defect, P4)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

It wouldn't be hard to cause assertions for *most* cases where people use
statically constructed XPCOM objects.  It could be done by:

 * adding (if they aren't there already) methods to nsTraceRefcnt to access the
number of bytes allocated and the number freed
 * checking that these numbers don't change around:
     * calls to PR_LoadLibrary and PR_UnloadLibrary in nsDll
     * all atexit functions (since that's how statics in function scope are
implemented on Linux, at least), by writing 2 functions, one called atexit() in
NS_InitXPCOM2, and the other in NS_ShutdownXPCOM, that compare the numbers
between when these 2 are called.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: preliminary patch

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

This has been checked in (see bug 61243) but not yet enabled.

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Well, I now have enough of these removed in my tree to see that there are
threadsafety problems with this patch (wow, what a surprise).  Perhaps the way
to fix the problem is to store the thread on which we're loading a library and
only assert if the allocation is on that thread too...

Comment 4

[Benjamin Smedberg]

I think this is working now, threadsafely even.