External Issue: Array assignment of BlockDist arrays segfaults, forall zip does not

18747, "jlbyrne-hpe", "Array assignment of BlockDist arrays segfaults, forall zip does not", "2021-11-18T21:51:05Z"

// segfaults
region.array = array;
 // works
forall (d,s) in zip(region.array, array) do
   d = s;

Steps to Reproduce

Source Code: spam.chpl

module Spam {
    use BlockDist;
    use CPtr;
    use IO;
    use IO.FormattedIO;
    use Reflection;

    type region_desc = c_ptr(void);

    class Sam {
        proc lookup_region(regionName:string): region_desc throws {
            return c_nil;

    class Region {
        const regionName: string;
        var regionDescs = newBlockArr({0..#numLocales}, region_desc);
        const size: uint(64);
        var iAmDestroyed = false;

        proc init(regionName: string, size: uint(64)) {
            this.regionName = regionName;
            this.size = size;


    // An attempted workaround for typing and initialization issues
    // I thought because I initialized Region.regionDescs the declaration
    // that something was getting confused about initialization and assignment
    // in init(). This didn't change things, though.
    proc newSharedRegion(regionName: string, size: uint(64),
                         ref regionDescs: [] region_desc) throws {
        try! stderr.writeln("%s %i".format(getRoutineName(), getLineNumber()));
        var region = new shared Region(regionName, size);
        try! stderr.writeln("%s %i".format(getRoutineName(), getLineNumber()));
        // This segfaults for me.
        region.regionDescs = regionDescs;
        // This doesn't.
        // forall (d, s) in zip(region.regionDescs, regionDescs) do
        //    d = s;
        try! stderr.writeln("%s %i".format(getRoutineName(), getLineNumber()));
        return region;

    var sammy = new Sam();

    private proc regionLookups(ref regionDescs, regionName: string) throws {
        // Won't break if the try isn't there.
        try {
            // The "with in" seems to be required as well
            forall r in regionDescs {
                var rName = regionName;
                r = sammy.lookup_region(rName);

    private proc lookup(regionName: string) throws {
        var regionDescs = newBlockArr(0..#numLocales, region_desc);
        regionLookups(regionDescs, regionName);

        return newSharedRegion(regionName, 1024, regionDescs);

    proc main() : int {
        try! lookup("a");

        return 0;

Compile command:
chpl -o spam spam.chpl

Execution command:
./spam -nl 1

Configuration Information

  • Output of chpl --version:
    chpl version 1.25.0
    built with LLVM version 11.0.1
  • Output of $CHPL_HOME/util/printchplenv --anonymize:
    CHPL_TARGET_ARCH: x86_64
    CHPL_TARGET_CPU: native *
    CHPL_COMM: none *
    CHPL_TASKS: qthreads
    CHPL_TIMERS: generic
    CHPL_UNWIND: none
    CHPL_MEM: jemalloc
    CHPL_ATOMICS: cstdlib
    CHPL_GMP: bundled
    CHPL_HWLOC: bundled
    CHPL_RE2: bundled *
    CHPL_LLVM: bundled *
  • Back-end compiler and version, e.g. gcc --version or clang --version:
    clang version 11.0.1 (git@github.hpe.com:john-l-byrne/chapel.git 400cb9af1a54df5ae00a106bd7404c15657be9ac)
    Target: x86_64-unknown-linux-gnu
    Thread model: posix