DN464078840

Subject: Re: Tcl_Eval and reentrancy - DN [1]

Scott Redman <redman@scriptics.com> - 08 Apr 1999 - comp.lang.tcl

 David Gravereaux wrote:
 >
 > Scott Redman <redman@scriptics.com> wrote:
 >
 > >DO NOT USE 8.0.x with multiple threads! It is NOT thread-safe.
 >
 > Scott, I do it all the time.
 >
 > Rather than expect 8.0.5 to be thread-safe, I sync my own threads to
 > work with Tcl's singlethreaded core.  Which for me, works fine.  I'm
 > quite happy with a singlethreaded core.
 >
 > * David Gravereaux *
 > Tomahawk Software Group
 > Mahalo Aloha from Maui, Hawai'i

 (for comp.lang.tcl readers)

 This will work, but you need to be careful not to call the interpreter
 or _any_ Tcl API fn's from more than one thread at a time (you need
 to guard ALL calls to Tcl_* with mutexes or semaphores from your code).

 Another way (8.0.x) is to guarantee that only one thread ever calls
 the Tcl_* functions.  Using 8.0.4, I wrote a simple queue where other
 threads placed scripts to execute in the interepreter into the queue,
 and I used events (Win32's CreateEvent()) to synchronize.  Data
 returned was always copied as a string and the return value.
 This worked fine.  But, 8.1 has this functionality built-in,
 plus it allows you to keep the result in TclObj form and
 call Tcl_ functions.

 If you haven't already worked around the lack of thread safety
 in 8.0.x, I'd highly recommend using 8.1 with --enable-threads
 turned on (on Windows, change the makefile.vc to uncomment the
 line "THREADDEFINES=-DTCL_THREADS=1").

 -- Scott Redman