Use coreutils to force-enable line buffering instead of depending on VM (#1771)

* GNU coreutils force-enabling line buffering instead of depending on VM to do buffering right

* remove debugging and wrong show-progress

* core dumps on

* pub get in script?

* skip install on macos

* syntax error fix

* travis

* fix syntax

* Remove if statement

* Fix up travis hack for better usefulness for dartdoc, and disable the hack on macos

* Make install_travis not return non-zero

Author: jcollins-g

.travis.yml

@@ -14,6 +14,17 @@ os:
   - osx
   - linux
 
+
+install:
+- ./tool/install_travis.sh
+
+before_script:
+- ulimit -c unlimited -S
+- pub get
+
+after_failure:
+- ./tool/after_failure_travis.sh
+
 before_install:
   # Disable non-blocking I/O for stdout, stderr https://github.com/travis-ci/travis-ci/issues/4704#issuecomment-348435959
   - python -c 'import os,sys,fcntl; flags = fcntl.fcntl(sys.stdout, fcntl.F_GETFL); fcntl.fcntl(sys.stdout, fcntl.F_SETFL, flags&~os.O_NONBLOCK);'

lib/src/io_utils.dart

@@ -186,7 +186,22 @@ class SubprocessLauncher {
 
     if (Platform.environment.containsKey('DRY_RUN')) return null;
 
-    Process process = await Process.start(executable, arguments,
+    String realExecutable = executable;
+    final List<String> realArguments = [];
+    if (Platform.isLinux) {
+      // Use GNU coreutils to force line buffering.  This makes sure that
+      // subprocesses that die due to fatal signals do not chop off the
+      // last few lines of their output.
+      //
+      // Dart does not actually do this (seems to flush manually) unless
+      // the VM crashes.
+      realExecutable = 'stdbuf';
+      realArguments.addAll(['-o', 'L', '-e', 'L']);
+      realArguments.add(executable);
+    }
+    realArguments.addAll(arguments);
+
+    Process process = await Process.start(realExecutable, realArguments,
         workingDirectory: workingDirectory, environment: environment);
     Future<void> stdoutFuture = _printStream(process.stdout, stdout,
         prefix: prefix, filter: jsonCallback);

tool/after_failure_travis.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+# Echo commands as they execute.
+set -x
+
+# Display backtrace for a single core.
+function do_core() {
+  local corefile="$1"
+
+  echo "Processing core file: $corefile"
+  gdb -c "$corefile" -ex "thread apply all bt" -ex "set pagination 0" -batch
+}
+
+# Find core files in likely locations for dartdoc.
+if uname | grep -q Linux ; then
+  COREFILES=$(find . -type f -name "core*" 2>/dev/null | egrep -v '(.yaml|.dart|.expect|.gni)$') # find core files
+  COREFILES_TMP="$(cd /tmp ; find . -type f -name "core*" 2>/dev/null | egrep -v '(.yaml|.dart|.expect|.gni)$')"
+  for f in ${COREFILES} ; do {
+    do_core "$f"
+  } ; done
+  for f in ${COREFILES_TMP} ; do {
+    do_core "/tmp/$f"
+  } ; done
+fi
+

tool/install_travis.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+# Echo commands as they execute.
+set -x
+
+if uname | grep -q Linux ; then
+  sudo apt-get install -y gdb
+fi
+
+exit 0