correct travis errors

.travis.yml

@@ -1,7 +1,6 @@
 language: cpp
 
 # Currently sudo is not required, NO ENV is used 
-sudo: false
 
 # Supported Operating systems
 #os:
@@ -15,6 +14,7 @@ matrix:
   include:
     - os: linux
     # Compiler is specified in ./travis/common.sh
+      sudo: false
       compiler: g++-4.9
       addons:
         apt:
@@ -55,6 +55,7 @@ matrix:
           - qt5-default
     - os: osx
       osx_image: xcode10.2 # we target latest MacOS Mojave
+      sudo: true
       compiler: gcc-4.9 # Use clang instead of gcc in MacOS
       addons:
         homebrew:

.travis/common.sh

@@ -27,17 +27,17 @@ function end_section() {
 	travis_fold end "$1"
 }
 
-# For Mac OS, we use g++-8 and gcc-8 as default compilers
+# For Mac OS, we use g++ and gcc as default compilers
 if [[ $TRAVIS_OS_NAME == 'osx' ]]; then
-  export CC=gcc-8
-  export CXX=g++-8
+  export CC=gcc
+  export CXX=g++
   # export PATH="/usr/local/opt/bison/bin:/usr/local/bin:$PATH"
   # export PATH="/usr/local/opt/qt/bin:$PATH"
   # Install header files in Mojave, if not gcc-4.9 cannot spot stdio.h
   sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /
 else 
-  # For linux, we use g++-6 and gcc-6 as default compilers
-  #export CC=gcc
-  #export CXX=g++
+  # For linux, we use g++-8 and gcc-8 as default compilers
+  export CC=gcc-8
+  export CXX=g++-8
 fi