[M3devel] malloc/free from Modula-3?

[Jay K]

Can you by chance see the other threads? I suspect not -- user threads I presume.
Can you try sprinking a lot more Disable/EnableSwitching around?
I guess you tried that..and..?

 - Jay


> From: hosking at cs.purdue.edu
> Date: Fri, 15 Apr 2011 11:26:15 -0400
> To: mika at async.caltech.edu
> CC: m3devel at elegosoft.com
> Subject: Re: [M3devel] malloc/free from Modula-3?
> 
> I suspect the problem is re-entrance to the library. Should you be disabling user thread switching somewhere?
> 
> Antony Hosking | Associate Professor | Computer Science | Purdue University
> 305 N. University Street | West Lafayette | IN 47907 | USA
> Office +1 765 494 6001 | Mobile +1 765 427 5484
> 
> 
> 
> 
> On Apr 15, 2011, at 6:37 AM, Mika Nystrom wrote:
> 
> > Hi m3devel,
> > 
> > I'm debugging a problem with some code I have that calls out to C
> > code.  It's calling pqlib (PostgreSQL library) and you might expect
> > things to go wrong there, but as it turns out it's dying in CM3's code.
> > 
> > The system is AMD64_LINUX (user threading because of the problems with
> > pthreads) and the program is just freezing up hard.  No segfault,
> > bus error or anything.  It locks up a couple of times a day.
> > 
> > What are the rules on calling malloc/free from Modula-3?
> > 
> > Stack trace:
> > 
> > (gdb) where
> > #0  0x00002ac519a9202e in ?? () from /lib/libc.so.6
> > #1  0x00002ac519a2fb43 in ?? () from /lib/libc.so.6
> > #2  0x00002ac519a2caab in free () from /lib/libc.so.6
> > #3  0x000000000091462f in Cstdlib__free (a=Cannot access memory at address 0x2ac73b0ef0d8
> > ) at ../src/C/Common/CstdlibC.c:26
> > #4  0x000000000091477d in M3toC__FreeCopiedS (s=Cannot access memory at address 0x2ac73b0ef0f8
> > ) at ../src/C/Common/M3toC.m3:46
> > #5  0x00000000007884f0 in UnsafeDatabase_M3_LINE_230.1181 (L_2=Cannot access memory at address 0x2ac73b0ef118
> > ) at ../src/UnsafeDatabase.m3:230
> > #6  0x000000000078881f in UnsafeDatabase__ExecM (t=Cannot access memory at address 0x2ac73b0ef148
> > ) at ../src/UnsafeDatabase.m3:228
> > #7  0x0000000000788aa6 in UnsafeDatabase__TExecM (t=Cannot access memory at address 0x2ac73b0ef268
> > ) at ../src/UnsafeDatabase.m3:258
> > #8  0x000000000077ad5b in DesynchronizedDB__SExec (t=Cannot access memory at address 0x2ac73b0ef328
> > ) at ../src/DesynchronizedDB.m3:126
> > #9  0x000000000077c190 in DesynchronizedDB__SMExec (t=Cannot access memory at address 0x2ac73b0ef3e8
> > ) at ../src/DesynchronizedDB.m3:293
> > #10 0x0000000000569367 in GCOMSOrderManager__OrderEntered (t=Cannot access memory at address 0x2ac73b0ef5a8
> > ) at ../src/GCOMSOrderManager.m3:596
> > #11 0x0000000000566b95 in GCOMSOrderManager__PlaceSingleOrder (t=Cannot access memory at address 0x2ac73b0ef668
> > ) at ../src/GCOMSOrderManager.m3:310
> > #12 0x000000000041ba25 in EuroDriver__OApply__PlaceOrder.1253 (price={<No data fields>}, count=Cannot access memory at address 0x2ac73b0ef7b8
> > ) at ../src/EuroDriver.m3:1108
> > #13 0x000000000041d97c in EuroDriver__OApply__MainLoop.1289 () at ../src/EuroDriver.m3:1401
> > #14 0x00000000004197a1 in EuroDriver__OApply (cl=Cannot access memory at address 0x2ac73b0efd38
> > ) at ../src/EuroDriver.m3:1545
> > #15 0x00000000009112c1 in ThreadPosix__RunThread () at ../src/thread/POSIX/ThreadPosix.m3:1174
> > #16 0x00002ac5199fa7b0 in ?? () from /lib/libc.so.6
> > #17 0x0000000000000000 in ?? ()
> > (gdb) 
> > 
> > Here is the code that causes the problem:
> > 
> >    VAR
> >      s := CopyTtoS(query);
> >    BEGIN
> >      TRY
> >        t.res := t.myExec(s,busyWait)
> >      FINALLY
> >        FreeCopiedS(s) (* stuck here *)
> >      END
> >    END;
> > 
> > The query is a SQL query---t.myExec eventually calls the libpq SQL exec
> > routine (PQexec I think it's called).
> > 
> > Since this is already an unsafe module I suppose I could just make an
> > array of CHARs on the stack and pass a pointer to that...
> > 
> > 
> >   Regards,
> >     Mika
> 
 		 	   		  
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