Segfault on 32-bit bytecode systems

[jamesjer]

I attempted to build polyml 5.9 for Fedora, but Tests/Succeed/Test160.ML segfaulted on the 32-bit ARM builder. Since that platform is the only 32-bit bytecode platform we build for, I tried passing --disable-native-codegeneration to configure on the 32-bit x86 builder to see if the crash is ARM-specific. It, too, segfaulted, so this seems to be a generic issue with 32-bit bytecode systems. This is what gdb has to say:

(gdb) run --script Tests/Succeed/Test160.ML
Thread 7 "poly" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xf587cac0 (LWP 96)]
0xf7f52292 in PolyObject::Get (i=0, this=<optimized out>) at /builddir/build/BUILD/polyml-5.9/libpolyml/globals.h:309
309	    PolyWord Get(POLYUNSIGNED i) const { return ((PolyWord*)this)[i]; }
(gdb) bt 
#0  0xf7f52292 in PolyObject::Get (i=0, this=<optimized out>)
    at /builddir/build/BUILD/polyml-5.9/libpolyml/globals.h:309
#1  ByteCodeInterpreter::RunInterpreter (this=<optimized out>, taskData=<optimized out>)
    at /builddir/build/BUILD/polyml-5.9/libpolyml/bytecode.cpp:846
#2  0xf7f77429 in IntTaskData::EnterPolyCode (this=0x83dc140)
    at /builddir/build/BUILD/polyml-5.9/libpolyml/interpreter.cpp:293
#3  NewThreadFunction (parameter=0x83dc140) at /builddir/build/BUILD/polyml-5.9/libpolyml/processes.cpp:1253
#4  0xf7dc1966 in start_thread (arg=<optimized out>) at pthread_create.c:434
#5  0xf7e4796c in clone3 () at ../sysdeps/unix/sysv/linux/i386/clone3.S:111

Given the comment on line 28 of Test160.ML about overflow, I tried defining just the random function, then ran "doFor random 100;". That triggered the segfault. I've been able to reduce it to this:

> Real.toInt IEEEReal.TO_NEGINF 1000000000.0;
val it = 1000000000: int
> Real.toInt IEEEReal.TO_NEGINF 1000000001.0;
Segmentation fault (core dumped)

[dcjm]

Thanks for reporting it and narrowing it down. The interpreter wasn't generating the Overflow exception properly in Real.toInt. This bug was also present in the 64-bit interpreter; it just wasn't triggered by this test. I'll add this fix to the fixes branch shortly.

[jamesjer]

Thank you for the quick fix!