itv::interval itv::interval_algebra::fPow(const itv::interval&, const itv::interval&): Assertion `x.lo() > 0' failed.

[jcelerier]

Hello !
I'm seeing this error crop up in various examples.

I haven't managed to reduce it so far, but it happens for instance on archlinux with the official faust package, when compiling the example distortion.dsp:

declare name "distortion";
declare version "0.0";
declare author "JOS, revised by RM";
declare description "Distortion demo application.";

import("stdfaust.lib");

process = dm.cubicnl_demo;

here's a stacktrace without debug info, I'm going to rebuild faust with debuginfo and give more precision

(gdb) bt
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=6, no_tid=0) at pthread_kill.c:44
#1  __pthread_kill_internal (threadid=<optimized out>, signo=6) at pthread_kill.c:78
#2  __GI___pthread_kill (threadid=<optimized out>, signo=signo@entry=6) at pthread_kill.c:89
#3  0x00007ffff1e417d8 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4  0x00007ffff1e2447b in __GI_abort () at abort.c:79
#5  0x00007ffff1e2439f in __assert_fail_base (
    fmt=0x7ffff1fbf620 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
    assertion=assertion@entry=0x7fffcb023d9e "x.lo() > 0",
    file=file@entry=0x7fffcb00ddb0 "/usr/src/debug/faust/faust-2.75.7/compiler/interval/intervalPow.cpp", line=line@entry=88,
    function=function@entry=0x7fffcb00dd58 "itv::interval itv::interval_algebra::fPow(const itv::interval&, const itv::interval&)") at assert.c:96
#6  0x00007ffff1e37de6 in __assert_fail (assertion=0x7fffcb023d9e "x.lo() > 0",
    file=0x7fffcb00ddb0 "/usr/src/debug/faust/faust-2.75.7/compiler/interval/intervalPow.cpp",
    line=88,
    function=0x7fffcb00dd58 "itv::interval itv::interval_algebra::fPow(const itv::interval&, const itv::interval&)") at assert.c:105
#7  0x00007fffcacbecbc in itv::interval_algebra::fPow(itv::interval const&, itv::interval const&) ()
   from /usr/lib/libfaust.so.2
#8  0x00007fffcacbef13 in itv::interval_algebra::Pow(itv::interval const&, itv::interval const&) ()
   from /usr/lib/libfaust.so.2
#9  0x00007fffcaca2472 in PowPrim::inferSigType(std::vector<P<AudioType>, std::allocator<P<AudioType> > > const&) () from /usr/lib/libfaust.so.2
#10 0x00007fffcae3b33b in ?? () from /usr/lib/libfaust.so.2

...

#23 0x00007fffcae3eb2f in ?? () from /usr/lib/libfaust.so.2
#24 0x00007fffcae41783 in typeAnnotation(CTreeBase*, bool) () from /usr/lib/libfaust.so.2
#25 0x00007fffcade420b in simplifyToNormalForm(CTreeBase*) () from /usr/lib/libfaust.so.2
#26 0x00007fffcac3fe3c in InstructionsCompiler::prepare(CTreeBase*) () from /usr/lib/libfaust.so.2
#27 0x00007fffcac01198 in DAGInstructionsCompiler::compileMultiSignal(CTreeBase*) ()
   from /usr/lib/libfaust.so.2
#28 0x00007fffcacce6f7 in ?? () from /usr/lib/libfaust.so.2
#29 0x00007fffcacd0fd4 in ?? () from /usr/lib/libfaust.so.2
#30 0x00007ffff1e9ec07 in start_thread (arg=<optimized out>) at pthread_create.c:447
#31 0x00007ffff1f2188c in __GI___clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78

[sletz]

Which faust version precisely ?

[jcelerier]

Reduction:

fails:

process(x) =  x * x;  

works:

process(x) =  x;  

FAUST Version 2.75.7
Embedded backends:
   DSP to C
   DSP to C++
   DSP to Cmajor
   DSP to Codebox
   DSP to CSharp
   DSP to DLang
   DSP to FIR
   DSP to Interpreter
   DSP to Java
   DSP to JAX
   DSP to Julia
   DSP to JSFX
   DSP to LLVM IR
   DSP to old C++
   DSP to Rust
   DSP to VHDL
   DSP to WebAssembly (wast/wasm)
Build with LLVM version 19.1.6
Copyright (C) 2002-2024, GRAME - Centre National de Creation Musicale. All rights reserved.

[jcelerier]

https://archlinux.org/packages/extra/x86_64/faust/ it's this package

[jcelerier]

that said it works on a simple example so maybe I'm having a case of multiple libraries that export symbols with the same name... investigating

[jcelerier]

ah! found the root cause.. it seems that compiling doesn't work when denormal fp numbers are disabled:

#include <cassert>
#include <iostream>

#include <faust/dsp/llvm-dsp.h>
int main(int argc, char** argv)
{
  _MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_ON);
  _MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
  std::string err;
  err.resize(4097);

  llvm_dsp_factory* fac{};

  {
    int argc = 0;
    const char* argv[] = {nullptr};
    fac = createDSPFactoryFromString(
        "score", "process(x) = x * x;", argc, argv, "", err, -1);
    assert(fac);

    auto obj = fac->createDSPInstance();
    assert(obj);

    obj->init(44100);
  }
}

[sletz]

Interesting... does not fail on ARM here. I'll have look ASAP.

[jcelerier]

I think it's fine to assume that denormal numbers should be on during compilation time, that said maybe this crash could be revealing some bug in the interval arithmetic calculation as I'd expect these assertions from a quick glance to hold either case. But I'm definitely not a deep IEEE754 expert aha