diff --git a/.appveyor.yml b/.appveyor.yml
index 8fa7379..07f5aa7 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -17,9 +17,9 @@ install:
 
 build_script:
 - cmd: if [%CONFIG%]==[cygwin64] (
-    C:\%CONFIG%\bin\bash -e -l -c "cd $APPVEYOR_BUILD_FOLDER && make gpscorrelate gpscorrelate-gui CFLAGS='-Wall -Wextra -O3 -DENABLE_NLS' LDFLAGS='-lintl'" )
+    C:\%CONFIG%\bin\bash -e -l -c "cd $APPVEYOR_BUILD_FOLDER && make gpscorrelate gpscorrelate-gui CXXFLAGS='-Wall -Wextra -O3 -DENABLE_NLS' CFLAGS='-Wall -Wextra -O3 -DENABLE_NLS' LDFLAGS='-lintl'" )
 - cmd: if [%CONFIG%]==[msys2] (
-    make EXEEXT=.exe gpscorrelate.exe gpscorrelate-gui.exe CC=gcc CXX=g++ CFLAGS="-Wall -Wextra -O3 -DENABLE_NLS" LDFLAGS="-lintl" )
+    make EXEEXT=.exe gpscorrelate.exe gpscorrelate-gui.exe CC=gcc CXX=g++ CFLAGS="-Wall -Wextra -O3 -DENABLE_NLS" CXXFLAGS="-Wall -Wextra -O3 -DENABLE_NLS" LDFLAGS="-lintl" )
 
 test_script:
 # Cygwin allows overwriting read-only files for some strange reason, which
diff --git a/.cirrus.yml b/.cirrus.yml
index e23e4eb..cd2ec00 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -29,7 +29,7 @@ freebsd_task:
     - pkg install -y pkgconf docbook-xsl exiv2 libxml2 gtk"$GTK" libxslt gettext-tools desktop-file-utils
 
   compile_script:
-    - make CC="$CC" CXX="$CXX" CFLAGS="$CFLAGS" LDFLAGS="$LDFLAGS" GTK="$GTK"
+    - make CC="$CC" CXX="$CXX" CFLAGS="$CFLAGS" CXXFLAGS="$CFLAGS" LDFLAGS="$LDFLAGS" GTK="$GTK"
 
   test_script:
     - ./gpscorrelate -V
@@ -70,7 +70,7 @@ linux_arm_task:
     - adduser build
 
   compile_script:
-    - make CC="$CC" CXX="$CXX" CFLAGS="$CFLAGS" LDFLAGS="$LDFLAGS" GTK="$GTK"
+    - make CC="$CC" CXX="$CXX" CFLAGS="$CFLAGS" CFLAGS="$CXXFLAGS" LDFLAGS="$LDFLAGS" GTK="$GTK"
 
   test_script:
     - ./gpscorrelate -V
@@ -113,7 +113,7 @@ linux_musl_task:
     - adduser -D build
 
   compile_script:
-    - make CC="$CC" CXX="$CXX" CFLAGS="$CFLAGS" LDFLAGS="$LDFLAGS" GTK="$GTK"
+    - make CC="$CC" CXX="$CXX" CFLAGS="$CFLAGS" CXXFLAGS="$CFLAGS" LDFLAGS="$LDFLAGS" GTK="$GTK"
 
   test_script:
     - ./gpscorrelate -V
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7178669..7fcf8c3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -79,7 +79,7 @@ jobs:
     - name: 'install deps'
       run: sudo apt-get update -y; sudo apt-get install -y --no-install-suggests --no-install-recommends ${{ matrix.build.install }}
     - name: 'build'
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
     - name: 'smoke test'
       # ASAN_OPTIONS is to work around https://bugzilla.redhat.com/show_bug.cgi?id=1950244
       run: env ASAN_OPTIONS="${{ matrix.build.asan_options }}" ./gpscorrelate -V
@@ -203,7 +203,7 @@ jobs:
     - name: 'install deps'
       run: sudo apt-get update -y; sudo apt-get install -y --no-install-suggests --no-install-recommends ${{ matrix.build.install }}
     - name: 'build'
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cflags }}"LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
     - name: 'smoke test'
       run: ./gpscorrelate -V
     - name: 'test'
@@ -236,7 +236,7 @@ jobs:
     - name: 'install deps'
       run: sudo apt-get update -y; sudo apt-get install -y --no-install-suggests --no-install-recommends ${{ matrix.build.install }}
     - name: 'build'
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
     - name: 'smoke test'
       run: ./gpscorrelate -V
     - name: 'test'
@@ -260,14 +260,16 @@ jobs:
           gtk: 2
           install: desktop-file-utils docbook-xsl exiv2 gtk+
           cflags: -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
+          cxxflags: -std=c++11 -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
           ldflags: -O3 -lintl
           cxx: g++
           target: all
           install_target: install install-po install-desktop-file
         - cc: gcc
           gtk: 3
-          install: desktop-file-utils docbook-xsl exiv2 gtk+3
+          install: -std=c++11 desktop-file-utils docbook-xsl exiv2 gtk+3
           cflags: -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
+          cxxflags: -std=c++11 -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
           ldflags: -O3 -lintl
           cxx: g++
           target: all
@@ -276,6 +278,7 @@ jobs:
           gtk: 2
           install: desktop-file-utils docbook-xsl exiv2 gtk+
           cflags: -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
+          cxxflags: -std=c++11 -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
           ldflags: -O3 -lintl
           cxx: clang++
           target: all
@@ -284,6 +287,7 @@ jobs:
           gtk: 3
           install: desktop-file-utils docbook-xsl exiv2 gtk+3
           cflags: -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
+          cxxflags: -std=c++11 -Wall -Wextra -Werror -Wno-error=deprecated-declarations -O3 -DENABLE_NLS=1
           ldflags: -O3 -lintl
           cxx: clang++
           target: all
@@ -294,7 +298,7 @@ jobs:
     - name: install deps
       run: brew install ${{ matrix.build.install }}
     - name: build
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} XML_CATALOG_FILES="$(brew --prefix)/etc/xml/catalog" XSLTFLAGS=--nonet ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cxxflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} XML_CATALOG_FILES="$(brew --prefix)/etc/xml/catalog" XSLTFLAGS=--nonet ${{ matrix.build.target }}
     - name: smoke test
       run: ./gpscorrelate -V
     - name: test
@@ -355,7 +359,7 @@ jobs:
     - name: install deps
       run: brew install ${{ matrix.build.install }}
     - name: build
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} XML_CATALOG_FILES="$(brew --prefix)/etc/xml/catalog" XSLTFLAGS=--nonet ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} XML_CATALOG_FILES="$(brew --prefix)/etc/xml/catalog" XSLTFLAGS=--nonet ${{ matrix.build.target }}
     - name: smoke test
       run: ./gpscorrelate -V
     - name: test
@@ -391,7 +395,7 @@ jobs:
       run: |
         dnf install -y --setopt=install_weak_deps=False ${{ matrix.build.install }}
     - name: build
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
     - name: smoke test
       run: ./gpscorrelate -V
     - name: test
@@ -428,7 +432,7 @@ jobs:
       run: |
         dnf install -y --setopt=install_weak_deps=False ${{ matrix.build.install }}
     - name: build
-      run: make CFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
+      run: make CFLAGS="${{ matrix.build.cflags }}" CXXFLAGS="${{ matrix.build.cflags }}" LDFLAGS="${{ matrix.build.ldflags }}" CC="${{ matrix.build.cc }}" CXX="${{ matrix.build.cxx }}" GTK="${{ matrix.build.gtk }}" ${{ matrix.build.make_opts }} ${{ matrix.build.target }}
     - name: smoke test
       run: ./gpscorrelate -V
     - name: test