Problem: Travis uses old-old-old-stable Ubuntu by default

Solution: set default to bionic, and leave a few jobs that manually
set Trusty/Xenial to have more coverage
This is especially useful to get newer gcc for address sanitizer support

.travis.yml

@@ -6,7 +6,7 @@ os:
 - linux
 - osx
 
-dist: trusty
+dist: bionic
 
 cache: ccache
 
@@ -98,14 +98,6 @@ matrix:
     os: osx
   - env: BUILD_TYPE=default CURVE=tweetnacl DRAFT=enabled ADDRESS_SANITIZER=enabled
     os: linux
-    dist: trusty
-    addons:
-      apt:
-        sources:
-        - sourceline: 'ppa:ubuntu-toolchain-r/test'
-        packages:
-        - g++-6
-        - gcc-6
   - env: BUILD_TYPE=android CURVE=tweetnacl
     os: linux
     dist: trusty
@@ -113,9 +105,6 @@ matrix:
     os: linux
     addons:
       apt:
-        sources:
-        - llvm-toolchain-trusty-8
-        - ubuntu-toolchain-r-test
         packages:
         - clang-format-8
   - env: BUILD_TYPE=default POLLER=poll

ci_build.sh

@@ -18,11 +18,6 @@ if [ $BUILD_TYPE == "default" ]; then
 
     if [ -n "$ADDRESS_SANITIZER" ] && [ "$ADDRESS_SANITIZER" == "enabled" ]; then
         CONFIG_OPTS+=("--enable-address-sanitizer=yes")
-        CONFIG_OPTS+=("CXX=g++-6")
-        CONFIG_OPTS+=("CC=gcc-6")
-        # workaround for linker problem with ASAN options in GCC
-        # http://stackoverflow.com/questions/37603238/fsanitize-not-using-gold-linker-in-gcc-6-1
-        CONFIG_OPTS+=("LDFLAGS=-fuse-ld=gold")
         # distcheck does an out-of-tree build, and the fuzzer tests use a hard-coded relative path for simplicity
         CHECK="check"
     fi