Adds a c++17 build using the pre-release Ubuntu 18.04.

Though given 00d87f8fe4 I would say this is better than nothing.

(cherry-picked from commit 33ad6be326)

.travis.yml

@@ -14,6 +14,9 @@ matrix:
     - compiler: gcc
       env: TOOL=scons CXXSTD=14 NLS=true LTS=1604 BRANCH=master
 
+    - compiler: gcc
+      env: TOOL=scons CXXSTD=17 NLS=false LTS=1804 BRANCH=master
+
     - compiler: gcc
       env: TOOL=scons CXXSTD=14 NLS=false LTS=1604 BRANCH=master OPT=-O0
 

docker/Dockerfile-base-1804-master

@@ -0,0 +1,19 @@
+FROM ubuntu:18.04
+
+RUN apt update
+
+RUN apt install -y -qq apt-utils
+
+# boost
+RUN apt install -y -qq libboost-filesystem1.65-dev libboost-filesystem1.65.1 libboost-iostreams1.65-dev libboost-iostreams1.65.1 libboost-locale1.65-dev libboost-locale1.65.1 libboost-regex1.65-dev libboost-regex1.65.1 libboost-serialization1.65-dev libboost-serialization1.65.1 libasio-dev libboost-program-options1.65-dev libboost-program-options1.65.1 libboost-random1.65-dev libboost-random1.65.1 libboost-system1.65-dev libboost-system1.65.1 libboost-test-dev
+
+# SDL
+RUN apt install -y -qq libsdl2-2.0-0 libsdl2-dev libsdl2-image-2.0-0 libsdl2-image-dev libsdl2-mixer-2.0-0 libsdl2-mixer-dev
+
+# misc
+RUN apt install -y -qq libpng16-16 libpng-dev libreadline6-dev libvorbis-dev libcairo2 libcairo2-dev libpango-1.0-0 libpango1.0-dev libfribidi0 libfribidi-dev libbz2-1.0 libbz2-dev zlib1g zlib1g-dev libpangocairo-1.0-0 libssl-dev
+
+# programs
+RUN apt install -y -qq openssl gdb xvfb bzip2 git scons cmake make ccache gcc g++ clang
+
+WORKDIR /home/wesnoth-travis

run_wml_tests

@@ -188,6 +188,12 @@ run_test()
   fi
   $command 2> error.log
   error_code="$?"
+  # workaround to fix issue in travis+18.04
+  while grep -q 'Could not initialize SDL_video' error.log; do
+    echo "Could not initialize SDL_video error, retrying..."
+    $command 2> error.log
+    error_code="$?"
+  done
   if check_errs $2 $error_code $1; then
     FirstTest=0 #Only start using validcache flag when at least one test has passed without error
     handle_error_log 0
@@ -376,3 +382,4 @@ else
   echo "All tests gave the correct result."
   exit 0
 fi
+

utils/travis/play_test_executor.sh

@@ -1,3 +1,12 @@
 #!/bin/bash
-set -e
-gdb -q -batch -return-child-result -ex "run" -ex "thread apply all bt" -ex "quit" --args ./wesnoth -m --controller 1:ai --controller 2:ai --nogui
+gdb -q -batch -return-child-result -ex "run" -ex "thread apply all bt" -ex "quit" --args ./wesnoth -m --controller 1:ai --controller 2:ai --nogui 2> error.log
+error_code="$?"
+while grep -q 'Could not initialize SDL_video' error.log; do
+  echo "Could not initialize SDL_video error, retrying..."
+  gdb -q -batch -return-child-result -ex "run" -ex "thread apply all bt" -ex "quit" --args ./wesnoth -m --controller 1:ai --controller 2:ai --nogui 2> error.log
+  error_code="$?"
+done
+cat error.log
+
+exit $error_code
+

utils/travis/test_executor.sh

@@ -1,3 +1,12 @@
 #!/bin/bash
-set -e
-gdb -q -batch -return-child-result -ex "run" -ex "thread apply all bt" -ex "quit" --args ./boost_unit_tests
+gdb -q -batch -return-child-result -ex "run" -ex "thread apply all bt" -ex "quit" --args ./boost_unit_tests 2> error.log
+error_code="$?"
+while grep -q 'Could not initialize SDL_video' error.log; do
+  echo "Could not initialize SDL_video error, retrying..."
+  gdb -q -batch -return-child-result -ex "run" -ex "thread apply all bt" -ex "quit" --args ./boost_unit_tests 2> error.log
+  error_code="$?"
+done
+cat error.log
+
+exit $error_code
+