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* Update redbean SQLite config to handle more options This requires moving sqlite3_initialize call to open, as configuration should be allowed before initialization is done. This call is effective only for the first time and then no-op after that. * Fix redbean SQLite for closing db with already finalized statements There is a loop in cleanupdb that finalizes all vms that are associated with that db when it's being closed. Under some circumstances (detailed below) that loop may contain references pointing to already collected objects, thus leading to SIGSEGV when those references are used. This may happen with the following sequence of events ("VM" is the name used in lsqlite and describes the same thing as "statement"): 1. A finalized statement is created (for example, by preparing an empty string or a string with no statement that is still grammatically valid). 2. This statement goes out of scope before the DB object it's associated with does and is garbage collected. 3. When it's garbage collected, dbvm_gc method is called, which checks for svm->vm being not NULL. 4. Since the VM is already finalized, cleanupvm method is not called, so the VM reference is not removed from the table of VMs tracked for that DB. 5. When the DB is finally closed or garbage collected, all the VMs associated with it are accessed to be finalized, including the ones that have been garbage collected and have invalid references (thus leading to a memory access error). Here is an example of a stacktrace from the resulting SIGSEGV: 70000003de20 5df71a getgeneric+26 70000003fac0 5dfc7f luaH_get+111 70000003faf0 5e06c8 luaH_set+40 70000003fb20 5c5bd7 aux_rawset+55 70000003fb50 5c70cb lua_rawset+27 70000003fb60 4fa8e7 cleanupvm+71 70000003fb80 4fa988 cleanupdb+88 70000003fbc0 4fe899 db_gc+41 One way to fix this is to use userdata references (which anchor their targets) instead of lightuserdata references (which do not), but this would prevent the targets (VMs) from being garbage collected until the DB itself is garbage collected, so this needs to be combined with weakening the keys in the DB table. The code in cleanupdb to remove the VM references is no longer needed, as this is handled by having weak keys. The patch also switches to using close_v2, as it is intended for use with garbage collected languages where the order in which destructors are called is arbitrary, as is the case here. * Remove GC collection from redbean SQLite session The behavior of sqlite3session_delete is undefined after the DB connection is closed, so we need to avoid calling it from gc handler. |
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