Allocate memory using the Tcl library's memory allocation engine. Like `malloc`, but integrates with the [memory] command (if that's defined). Pairs up with [Tcl_Realloc] and [Tcl_Free]. '''`Tcl_Alloc`''' and '''`Tcl_Realloc`''' ''guarantee'' to always return a valid block of memory; they will '''panic''' (call [Tcl_Panic]) if memory allocation fails. For alternatives that return ''`NULL`'', use '''`Tcl_AttemptAlloc`''' and '''`Tcl_AttemptRealloc`'''. See also the '''[http://www.tcl.tk/man/tcl/TclLib/Alloc.htm%|%manual]'''. (Note: the manual does not mention Tcl_Panic) (2022-10-25 from <aku> in the #tcl chat): [Tcl_Obj] are allocated in thread-local memory pools, and are thus (implicitly) owned by the thread allocating it. Releasing it in a different thread should break things. Because the pool is thread-local access is not mutex protected, there is the expectation that no other thread accesses it, and your [Tcl_DecrRefCount] from the other thread violates this assumption. In other words: don't Tcl_Alloc/ckalloc something in one thread to release it in another thread. <<categories>>Tcl C API