ci: try to get stack trace from mptest

Author: ryanofsky

ci/configs/gnu32.bash

@@ -4,6 +4,6 @@ NIX_ARGS=(
   --arg minimal true
   --arg crossPkgs 'import <nixpkgs> { crossSystem = { config = "i686-unknown-linux-gnu"; }; }'
 )
-export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter"
+export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter -ggdb"
 CMAKE_ARGS=(-G Ninja)
 BUILD_ARGS=(-k 0)

ci/scripts/ci.sh

@@ -34,4 +34,5 @@ else
     cmake --build . --target "$t" -- "${BUILD_ARGS[@]+"${BUILD_ARGS[@]}"}"
   done
 fi
+ulimit -c unlimited || true
 ctest --output-on-failure

ci/scripts/run.sh

@@ -8,6 +8,119 @@ export LC_ALL=C.UTF-8
 
 set -o errexit -o nounset -o pipefail -o xtrace
 
+echo "::group::Enable core dumps"
+
+# Try to ensure cores are written as files (not to systemd-coredump/apport).
+# This typically requires root; it's okay if it fails — we'll fall back to coredumpctl.
+want_pattern='core.%e.%p.%t'
+have_sudo=0
+if command -v sudo >/dev/null 2>&1; then have_sudo=1; fi
+if [[ -r /proc/sys/kernel/core_pattern ]]; then
+  current="$(cat /proc/sys/kernel/core_pattern || true)"
+  if [[ "$current" == '|'* ]]; then
+    # Piped to a handler; try to switch to file-based cores
+    if (( have_sudo )); then sudo sysctl -w "kernel.core_pattern=$want_pattern" || true; fi
+  else
+    # Already file-based; try to make the name more informative
+    if (( have_sudo )); then sudo sysctl -w "kernel.core_pattern=$want_pattern" || true; fi
+  fi
+fi
+
+echo "core_pattern now: $(cat /proc/sys/kernel/core_pattern 2>/dev/null || echo '?')"
+echo "::endgroup::"
+
 [ "${CI_CONFIG+x}" ] && source "$CI_CONFIG"
 
-nix-shell --pure --keep CI_CONFIG --keep CI_CLEAN "${NIX_ARGS[@]+"${NIX_ARGS[@]}"}" --run ci/scripts/ci.sh shell.nix
+status=0
+if ! nix-shell --pure --keep CI_CONFIG --keep CI_CLEAN "${NIX_ARGS[@]+"${NIX_ARGS[@]}"}" --run ci/scripts/ci.sh shell.nix; then
+  status=$?
+  echo "ci.sh failed with status $status"
+fi
+
+# --- Collect core files (file-based) -----------------------------------------
+echo "::group::Search for core files"
+mapfile -t cores < <(find "${GITHUB_WORKSPACE:-$PWD}" -xdev \
+  \( -type f -name 'core' -o -name 'core.*' \) 2>/dev/null || true)
+echo "Found ${#cores[@]} possible core files."
+echo "::endgroup::"
+
+# --- If no file-based cores, try systemd-coredump (Ubuntu) -------------------
+use_coredumpctl=0
+if [[ "${#cores[@]}" -eq 0 ]] && command -v coredumpctl >/dev/null 2>&1; then
+  # List recent dumps for this workspace's binaries (best-effort heuristic).
+  # If you know the test binary name(s), set EXE_HINT to narrow it.
+  EXE_HINT="mptest"
+  echo "::group::Check systemd-coredump"
+  if [[ -n "$EXE_HINT" ]]; then
+    coredumpctl --no-pager list | grep -E "$EXE_HINT" || true
+  else
+    coredumpctl --no-pager list | head -n 50 || true
+  fi
+  echo "::endgroup::"
+  use_coredumpctl=1
+fi
+
+# --- Print backtraces --------------------------------------------------------
+echo "::group::Backtraces"
+
+backtrace_with_gdb () {
+  local exe="$1" core="$2"
+  if [[ -n "$exe" && -x "$exe" ]]; then
+    echo "Core: $core"
+    echo "Exe:  $exe"
+    gdb -batch "$exe" "$core" \
+      -ex 'set pagination off' \
+      -ex 'set print pretty on' \
+      -ex 'info threads' \
+      -ex 'thread apply all bt full' \
+      -ex 'quit' || true
+  else
+    echo "Core: $core (exe unknown or not executable; trying core-only mode)"
+    gdb -batch -c "$core" \
+      -ex 'set pagination off' \
+      -ex 'set print pretty on' \
+      -ex 'info threads' \
+      -ex 'info files' \
+      -ex 'thread apply all bt full' \
+      -ex 'quit' || true
+  fi
+}
+if [[ "${#cores[@]}" -gt 0 ]]; then
+  for core in "${cores[@]}"; do
+    # Try to extract the executable path that gdb discovers from the core
+    exe="$(gdb -batch -c "$core" -ex 'info files' 2>/dev/null | sed -n "s/^Core was generated by \`\(.*\)'.*$/\1/p" | head -n1 || true)"
+    backtrace_with_gdb "$exe" "$core"
+  done
+elif (( use_coredumpctl )); then
+  # If your tests produce a known binary name, set EXE_HINT to make this precise.
+  # Otherwise we grab the newest C/C++ dump and use that.
+  line="$(coredumpctl --no-pager --no-legend list | tail -n 1)"
+  if [[ -n "$EXE_HINT" ]]; then
+    line="$(coredumpctl --no-pager --no-legend list | grep -E "$EXE_HINT" | tail -n 1 || true)"
+  fi
+  if [[ -n "$line" ]]; then
+    pid="$(awk '{print $5}' <<<"$line" || true)"
+    exe_path="$(coredumpctl --no-pager info "$pid" \
+             | sed -n 's/^ *Executable: //p' \
+             | head -n1)"
+    # Dump that core to a file and analyze
+    out="core.from-coredumpctl.${pid:-unknown}"
+    if coredumpctl dump "${pid:-}" -o "$out" >/dev/null 2>&1; then
+      backtrace_with_gdb "$exe_path" "$out"
+    else
+      echo "Could not dump core via coredumpctl (pid=$pid)."
+      # As a last resort, coredumpctl can drive gdb directly, but it's interactive.
+      # We avoid that in CI.
+    fi
+    rm -v "$out"
+  else
+    echo "No matching coredumps in systemd-coredump."
+  fi
+else
+  echo "No core files found."
+fi
+
+echo "::endgroup::"
+
+# Preserve the original test result code
+exit "$status"

shell.nix

@@ -55,6 +55,7 @@ in crossPkgs.mkShell {
   ];
   nativeBuildInputs = with pkgs; [
     cmakeBuild
+    gdb
     include-what-you-use
     ninja
   ] ++ lib.optionals (!minimal) [

test/mp/test/test.cpp

@@ -29,6 +29,7 @@
 #include "mp/util.h"
 #include <optional>
 #include <set>
+#include <signal.h>
 #include <stdexcept>
 #include <string>
 #include <string_view>
@@ -67,6 +68,12 @@ class TestSetup
 
     TestSetup(bool client_owns_connection = true)
         : thread{[&] {
+              // Restore default sigsegv handler to enable core dumps
+              struct sigaction dfl{};
+              dfl.sa_handler = SIG_DFL;
+              sigemptyset(&dfl.sa_mask);
+              sigaction(SIGSEGV, &dfl, nullptr);
+
               EventLoop loop("mptest", [](mp::LogMessage log_data) {
                   std::cout << "LOG" << (int)log_data.level << ": " << log_data.message << "\n";
                   if (log_data.level == mp::Log::Raise) throw std::runtime_error(log_data.message);