diff --git a/.travis.yml b/.travis.yml
index a8b9e7c184..bb65a7824e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -228,7 +228,12 @@ _matrix_required_linux_pass3_large:
 # Ordered by variants expected to succeed to run first,
 # although with current Travis CI implementation, the env
 # blocks listed in allowed_failures only run after all
-# those not listed:
+# those not listed. Jobs which currently fail until code
+# gets fixed are conditional with "if: branch =~ fightwarn"
+# so users (and NUT upstream) can define a branch with a
+# name containing this keyword to work on bug fixes, but by
+# default the main development would not bother Travis CI
+# to waste resources in vain.
 #
 
 _matrix_linux_gnustd_nowarn:
@@ -344,6 +349,7 @@ _matrix_linux_cstd_nowarn:
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -360,6 +366,7 @@ _matrix_linux_cstd_nowarn:
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -376,6 +383,7 @@ _matrix_linux_cstd_nowarn:
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -392,6 +400,7 @@ _matrix_linux_cstd_nowarn:
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -404,45 +413,49 @@ _matrix_linux_cstd_nowarn:
 # Stuff with warnings made fatal... well, is usually fatal so far:
 _matrix_linux_gnustd_warn:
   include: &_matrix_linux_gnustd_warn
-  - env: NUT_MATRIX_TAG="cDefault-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic" CXXFLAGS="-Wall -Werror"
+  - env: NUT_MATRIX_TAG="cDefault-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic" CXXFLAGS="-Wall -Wextra -Werror"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="gnu99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Werror -std=gnu++99"
+  - env: NUT_MATRIX_TAG="gnu99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++99"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="gnu11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu11" CXXFLAGS="-Wall -Werror -std=gnu++11"
+  - env: NUT_MATRIX_TAG="gnu11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu11" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++11"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="gnu99-gcc-7-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Werror -std=gnu++99" CC=gcc-7 CXX=g++-7
+  - env: NUT_MATRIX_TAG="gnu99-gcc-7-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++99" CC=gcc-7 CXX=g++-7
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -452,12 +465,13 @@ _matrix_linux_gnustd_warn:
         - gcc-7
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="gnu17-gcc-9-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu17" CXXFLAGS="-Wall -Werror -std=gnu++17" CC=gcc-9 CXX=g++-9
+  - env: NUT_MATRIX_TAG="gnu17-gcc-9-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu17" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++17" CC=gcc-9 CXX=g++-9
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -468,12 +482,13 @@ _matrix_linux_gnustd_warn:
         - *deps_driverlibs
 
 # Note: Fixing these would make NUT viable again on platforms with only ANSI C!
-  - env: NUT_MATRIX_TAG="gnu89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu89" CXXFLAGS="-Wall -Werror -std=gnu++89"
+  - env: NUT_MATRIX_TAG="gnu89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu89" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++89"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
@@ -482,24 +497,26 @@ _matrix_linux_gnustd_warn:
 # The hardest of two worlds: both strict C standards on Linux and fatal warnings:
 _matrix_linux_cstd_warn:
   include: &_matrix_linux_cstd_warn
-  - env: NUT_MATRIX_TAG="c99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99"
+  - env: NUT_MATRIX_TAG="c99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -std=c++99"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="c99-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c99-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++99" CC=clang CXX=clang++
     os: linux
     dist: xenial
     sudo: false
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -509,13 +526,14 @@ _matrix_linux_cstd_warn:
         - clang-format-5.0
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="c11-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c11" CXXFLAGS="-Wall -Werror -std=c++11" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c11-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c11" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++11" CC=clang CXX=clang++
     os: linux
     dist: xenial
     sudo: false
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -525,13 +543,14 @@ _matrix_linux_cstd_warn:
         - clang-format-5.0
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="c17-clang-8-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c17" CXXFLAGS="-Wall -Werror -std=c++17" CC=clang-8 CXX=clang++-8
+  - env: NUT_MATRIX_TAG="c17-clang-8-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++17" CC=clang-8 CXX=clang++-8
     os: linux
     dist: xenial
     sudo: false
     services:
         - docker
     compiler: clang
+    if: branch =~ fightwarn
     addons:
       apt:
         sources:
@@ -541,23 +560,25 @@ _matrix_linux_cstd_warn:
         - clang-format-8
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="c11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c11" CXXFLAGS="-Wall -Werror -std=c++11"
+  - env: NUT_MATRIX_TAG="c11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=c11" CXXFLAGS="-Wall -Wextra -Werror -std=c++11"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
         - *deps_driverlibs
 
-  - env: NUT_MATRIX_TAG="c89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c89" CXXFLAGS="-Wall -Werror -std=c++89"
+  - env: NUT_MATRIX_TAG="c89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=c89" CXXFLAGS="-Wall -Wextra -Werror -std=c++89"
     os: linux
     sudo: false
     services:
         - docker
     compiler: gcc
+    if: branch =~ fightwarn
     addons:
       apt:
         packages:
@@ -596,19 +617,21 @@ _matrix_osx_gnustd_nowarn:
 
 _matrix_osx_gnustd_warn:
   include: &_matrix_osx_gnustd_warn
-  - env: NUT_MATRIX_TAG="gnu99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Werror -std=gnu++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="gnu99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=gnu99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=gnu++99" CC=clang CXX=clang++
     os: osx
     osx_image: xcode10.2
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
       - $HOME/.ccache
 
-  - env: NUT_MATRIX_TAG="gnu17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu17" CXXFLAGS="-Wall -Werror -std=gnu++17" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="gnu17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=gnu17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=gnu++17" CC=clang CXX=clang++
     os: osx
     osx_image: xcode10.2
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
@@ -620,6 +643,7 @@ _matrix_osx_cstd_nowarn:
     os: osx
     osx_image: xcode10.2
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
@@ -629,6 +653,7 @@ _matrix_osx_cstd_nowarn:
     os: osx
     osx_image: xcode10.2
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
@@ -636,28 +661,31 @@ _matrix_osx_cstd_nowarn:
 
 _matrix_osx_cstd_warn:
   include: &_matrix_osx_cstd_warn
-  - env: NUT_MATRIX_TAG="c99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++99" CC=clang CXX=clang++
     os: osx
     osx_image: xcode10.2
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
       - $HOME/.ccache
 
-  - env: NUT_MATRIX_TAG="c17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c17" CXXFLAGS="-Wall -Werror -std=c++17" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++17" CC=clang CXX=clang++
     os: osx
     osx_image: xcode10.2
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
       - $HOME/.ccache
 
-  - env: NUT_MATRIX_TAG="c17-clang-xcode7.3-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c17" CXXFLAGS="-Wall -Werror -std=c++17" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c17-clang-xcode7.3-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++17" CC=clang CXX=clang++
     os: osx
     osx_image: xcode7.3
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/Library/Caches/Homebrew
@@ -674,6 +702,7 @@ _matrix_windows_gnustd_nowarn:
   - env: NUT_MATRIX_TAG="gnu99-clang-win-nowarn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-std=gnu99" CXXFLAGS="-std=gnu++99" CC=clang CXX=clang++
     os: windows
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/AppData/Local/Temp/chocolatey
@@ -685,6 +714,7 @@ _matrix_windows_cstd_nowarn:
   - env: NUT_MATRIX_TAG="c99-clang-win-nowarn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-std=c99" CXXFLAGS="-std=c++99" CC=clang CXX=clang++
     os: windows
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/AppData/Local/Temp/chocolatey
@@ -693,9 +723,10 @@ _matrix_windows_cstd_nowarn:
 
 _matrix_windows_cstd_warn:
   include: &_matrix_windows_cstd_warn
-  - env: NUT_MATRIX_TAG="c99-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c99-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++99" CC=clang CXX=clang++
     os: windows
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/AppData/Local/Temp/chocolatey
@@ -704,9 +735,10 @@ _matrix_windows_cstd_warn:
 
 # Incidentally, this is one platform we know to have clang-9,
 # the version which has (at least partial) C++20 support
-  - env: NUT_MATRIX_TAG="c20-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Werror -pedantic -std=c20" CXXFLAGS="-Wall -Werror -std=c++20" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c20-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c20" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++20" CC=clang CXX=clang++
     os: windows
     compiler: clang
+    if: branch =~ fightwarn
     cache:
       directories:
       - $HOME/AppData/Local/Temp/chocolatey
@@ -776,8 +808,11 @@ _matrix_cstd_nowarn:
   - *_matrix_linux_cstd_nowarn
   - *_matrix_osx_cstd_nowarn
   - *_matrix_windows_cstd_nowarn
-###  - *_matrix_osx_gnustd_nowarn
-###  - *_matrix_linux_gnustd_nowarn
+
+_matrix_gnustd_nowarn:
+  include: &_matrix_gnustd_nowarn
+  - *_matrix_osx_gnustd_nowarn
+  - *_matrix_linux_gnustd_nowarn
 
 _matrix_warn:
   include: &_matrix_warn
@@ -803,11 +838,12 @@ _matrix_all:
 _matrix_master:
   include: &_matrix_master
   - *_matrix_required
-### Enable for branch builds that intend to fix the issues which preclude
+### Enabled for branches with names containing "fightwarn" to perform
+### builds that intend to actively fix the issues which preclude the
 ### following items from becoming green:
-#  - *_matrix_allowfail_linux
-#  - *_matrix_allowfail_osx
-#  - *_matrix_windows
+  - *_matrix_allowfail_linux
+  - *_matrix_allowfail_osx
+  - *_matrix_windows
 
 _matrix_fixbugs:
   include: &_matrix_fixbugs
@@ -821,10 +857,11 @@ _matrix_fixbugs:
 #
 # DO NOT COMMIT TO MASTER BRANCH TEST-MATRICES THAT ARE NOT _matrix-master!
 #
-# These days, "jobs" and "matrix" are same thing... at least, ours is an explicit list.
+# These days, "jobs" and "matrix" (Travis keywords) are same thing... at least,
+# ours is an explicit list.
 # By "fast_finish" we allow to assign a verdict based on completion of required
 # test cases. The "allow_failures" will proceed to run for our information
-# but not block nor delay PR considerations etc.
+# but should not block nor delay PR considerations etc.
 jobs:
   fast_finish: true
   include:
@@ -839,39 +876,39 @@ jobs:
 #OK#  - env: NUT_MATRIX_TAG="gnu17-gcc-9-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu17" CXXFLAGS="-std=gnu++17" CC=gcc-9 CXX=g++-9
 #OK#  - env: NUT_MATRIX_TAG="gnu99-clang-5.0-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu99" CXXFLAGS="-std=gnu++99" CC=clang CXX=clang++
 #OK#  - env: NUT_MATRIX_TAG="gnu17-clang-8-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu17" CXXFLAGS="-std=gnu++17" CC=clang-8 CXX=clang++-8
-  - env: NUT_MATRIX_TAG="gnu17-gcc-9-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu17" CXXFLAGS="-Wall -Werror -std=gnu++17" CC=gcc-9 CXX=g++-9
+  - env: NUT_MATRIX_TAG="gnu17-gcc-9-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu17" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++17" CC=gcc-9 CXX=g++-9
   - env: NUT_MATRIX_TAG="c99-clang-3.5-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=c99" CXXFLAGS="-std=c++99" CC=clang-3.5 CXX=clang++-3.5
   - env: NUT_MATRIX_TAG="c99-clang-5.0-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=c99" CXXFLAGS="-std=c++99" CC=clang CXX=clang++
   - env: NUT_MATRIX_TAG="c11-clang-5.0-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=c11" CXXFLAGS="-std=c++11" CC=clang CXX=clang++
   - env: NUT_MATRIX_TAG="c17-clang-8-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=c17" CXXFLAGS="-std=c++17" CC=clang-8 CXX=clang++-8
-  - env: NUT_MATRIX_TAG="c17-clang-8-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c17" CXXFLAGS="-Wall -Werror -std=c++17" CC=clang-8 CXX=clang++-8
-  - env: NUT_MATRIX_TAG="cDefault-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic" CXXFLAGS="-Wall -Werror"
-  - env: NUT_MATRIX_TAG="gnu99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Werror -std=gnu++99"
-  - env: NUT_MATRIX_TAG="c99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99"
-  - env: NUT_MATRIX_TAG="gnu99-gcc-7-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Werror -std=gnu++99" CC=gcc-7 CXX=g++-7
-  - env: NUT_MATRIX_TAG="c99-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c11-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c11" CXXFLAGS="-Wall -Werror -std=c++11" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c11" CXXFLAGS="-Wall -Werror -std=c++11"
-  - env: NUT_MATRIX_TAG="gnu11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu11" CXXFLAGS="-Wall -Werror -std=gnu++11"
+  - env: NUT_MATRIX_TAG="c17-clang-8-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++17" CC=clang-8 CXX=clang++-8
+  - env: NUT_MATRIX_TAG="cDefault-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic" CXXFLAGS="-Wall -Wextra -Werror"
+  - env: NUT_MATRIX_TAG="gnu99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++99"
+  - env: NUT_MATRIX_TAG="c99-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -std=c++99"
+  - env: NUT_MATRIX_TAG="gnu99-gcc-7-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++99" CC=gcc-7 CXX=g++-7
+  - env: NUT_MATRIX_TAG="c99-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c11-clang-5.0-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c11" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++11" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=c11" CXXFLAGS="-Wall -Wextra -Werror -std=c++11"
+  - env: NUT_MATRIX_TAG="gnu11-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu11" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++11"
 #OK#  - env: NUT_MATRIX_TAG="gnu89-gcc-default-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu89" CXXFLAGS="-std=gnu++89"
-  - env: NUT_MATRIX_TAG="c89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c89" CXXFLAGS="-Wall -Werror -std=c++89"
-  - env: NUT_MATRIX_TAG="gnu89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu89" CXXFLAGS="-Wall -Werror -std=gnu++89"
+  - env: NUT_MATRIX_TAG="c89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=c89" CXXFLAGS="-Wall -Wextra -Werror -std=c++89"
+  - env: NUT_MATRIX_TAG="gnu89-gcc-default-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -pedantic -std=gnu89" CXXFLAGS="-Wall -Wextra -Werror -std=gnu++89"
 ### macosx
 #OK#  - env: NUT_MATRIX_TAG="gnu99-clang-xcode10.2-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu99" CXXFLAGS="-std=gnu++99" CC=clang CXX=clang++
 #OK#  - env: NUT_MATRIX_TAG="gnu17-clang-xcode10.2-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu17" CXXFLAGS="-std=gnu++17" CC=clang CXX=clang++
 #OK#  - env: NUT_MATRIX_TAG="gnu99-clang-xcode7.3-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=gnu99" CXXFLAGS="-std=gnu++99" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="gnu99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu99" CXXFLAGS="-Wall -Werror -std=gnu++99" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="gnu17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=gnu17" CXXFLAGS="-Wall -Werror -std=gnu++17" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="gnu99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=gnu99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=gnu++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="gnu17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=gnu17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=gnu++17" CC=clang CXX=clang++
   - env: NUT_MATRIX_TAG="c99-clang-xcode10.2-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=c99" CXXFLAGS="-std=c++99" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c99-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++99" CC=clang CXX=clang++
   - env: NUT_MATRIX_TAG="c17-clang-xcode10.2-nowarn" BUILD_TYPE=default-all-errors CFLAGS="-std=c17" CXXFLAGS="-std=c++17" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c17" CXXFLAGS="-Wall -Werror -std=c++17" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c17-clang-xcode7.3-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Werror -pedantic -std=c17" CXXFLAGS="-Wall -Werror -std=c++17" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c17-clang-xcode10.2-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++17" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c17-clang-xcode7.3-warn" BUILD_TYPE=default-all-errors CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c17" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++17" CC=clang CXX=clang++
 ### windows
   - env: NUT_MATRIX_TAG="gnu99-clang-win-nowarn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-std=gnu99" CXXFLAGS="-std=gnu++99" CC=clang CXX=clang++
   - env: NUT_MATRIX_TAG="c99-clang-win-nowarn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-std=c99" CXXFLAGS="-std=c++99" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c99-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Werror -pedantic -std=c99" CXXFLAGS="-Wall -Werror -std=c++99" CC=clang CXX=clang++
-  - env: NUT_MATRIX_TAG="c20-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Werror -pedantic -std=c20" CXXFLAGS="-Wall -Werror -std=c++20" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c99-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c99" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++99" CC=clang CXX=clang++
+  - env: NUT_MATRIX_TAG="c20-clang-win-warn" BUILD_TYPE=default-all-errors CPPFLAGS="-fms-extensions" CFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -pedantic -std=c20" CXXFLAGS="-Wall -Wextra -Werror -Weverything -Wno-unused-macros -std=c++20" CC=clang CXX=clang++
 
 before_install:
 - |-
diff --git a/ci_build.sh b/ci_build.sh
index 1f0de7d4f5..181d071298 100755
--- a/ci_build.sh
+++ b/ci_build.sh
@@ -24,6 +24,28 @@ case "$CI_TRACE" in
         set -x ;;
 esac
 
+configure_nut() {
+    echo "=== CONFIGURING NUT: ./configure ${CONFIG_OPTS[*]}"
+    echo "=== CC='$CC' CXX='$CXX' CPP='$CPP'"
+    $CI_TIME ./configure "${CONFIG_OPTS[@]}" \
+    || { RES=$?
+        echo "FAILED ($RES) to configure nut, will dump config.log in a second to help troubleshoot CI" >&2
+        echo "    (or press Ctrl+C to abort now if running interactively)" >&2
+        sleep 1
+        echo "=========== DUMPING config.log :"; cat config.log || true ; echo "=========== END OF config.log"
+        echo "FATAL: FAILED ($RES) to ./configure ${CONFIG_OPTS[*]}" >&2
+        exit $RES
+       }
+}
+
+build_to_only_catch_errors() {
+    ( echo "`date`: Starting the parallel build attempt (quietly to build what we can)..."; \
+      $CI_TIME make VERBOSE=0 -k -j8 all >/dev/null 2>&1 ; ) || \
+    ( echo "`date`: Starting the sequential build attempt (to list remaining files with errors considered fatal for this build configuration)..."; \
+      $CI_TIME make VERBOSE=1 all -k ) || return $?
+    return 0
+}
+
 echo "Processing BUILD_TYPE='${BUILD_TYPE}' ..."
 case "$BUILD_TYPE" in
 default|default-alldrv|default-all-errors|default-spellcheck|default-shellcheck|default-nodoc|default-withdoc|"default-tgt:"*)
@@ -253,16 +275,14 @@ default|default-alldrv|default-all-errors|default-spellcheck|default-shellcheck|
     if [ "$TRAVIS_OS_NAME" = "windows" ] ; then
         $CI_TIME ./autogen.sh || true
     else
-        $CI_TIME ./autogen.sh 2>/dev/null
+        $CI_TIME ./autogen.sh ### 2>/dev/null
     fi
     if [ "$NO_PKG_CONFIG" == "true" ] && [ "$TRAVIS_OS_NAME" = "linux" ] ; then
         echo "NO_PKG_CONFIG==true : BUTCHER pkg-config for this test case" >&2
         sudo dpkg -r --force all pkg-config
     fi
 
-    echo "=== CONFIGURING NUT: ./configure ${CONFIG_OPTS[*]}"
-    echo "=== CC='$CC' CXX='$CXX' CPP='$CPP'"
-    $CI_TIME ./configure "${CONFIG_OPTS[@]}"
+    configure_nut
 
     case "$BUILD_TYPE" in
         "default-tgt:"*) # Hook for matrix of custom distchecks primarily
@@ -305,11 +325,9 @@ default|default-alldrv|default-all-errors|default-spellcheck|default-shellcheck|
             exit $?
             ;;
         "default-all-errors")
-            ( echo "`date`: Starting the parallel build attempt (quietly to build what we can)..."; \
-              $CI_TIME make VERBOSE=0 -k -j8 all >/dev/null 2>&1 ; ) || \
-            ( echo "`date`: Starting the sequential build attempt (to list remaining files with errors considered fatal for this build configuration)..."; \
-              $CI_TIME make VERBOSE=1 all -k )
-            exit $?
+            RES=0
+            build_to_only_catch_errors || RES=$?
+            exit $RES
             ;;
     esac
 
diff --git a/configure.ac b/configure.ac
index 9cae02bd57..a716653b10 100644
--- a/configure.ac
+++ b/configure.ac
@@ -996,7 +996,30 @@ dnl ----------------------------------------------------------------------
 dnl checks related to --with-dev
 
 dnl We only init libtool there to allow AC_DISABLE_STATIC
+if ( test "${GCC}" = "yes" )
+then
+	dnl # Avoid new compilers' warnings/errors about libtool distro flaws in this test like:
+	dnl #   error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
+	dnl #   {"nm_test_func", (void *) &nm_test_func},
+	dnl # or ones about LTO (-flto -fno-common) as discussed and suggested
+	dnl # in https://www.mail-archive.com/libtool@gnu.org/msg14037.html -
+	dnl # all leading to undefined "global_symbol_pipe" in the generated
+	dnl # libtool script, and resulting in errors like `... | | ...` below :
+	dnl # libtool: link: /usr/bin/nm -B .libs/upsclient.o \
+	dnl #   ../common/.libs/libcommonclient.a |  | /usr/bin/sed 's/.* //' \
+	dnl #   | sort | uniq > .libs/libupsclient.exp
+	dnl # ../libtool: syntax error: `|' unexpected
+
+	CFLAGS_SAVED_NOPEDANTIC="$CFLAGS"
+	AS_CASE(["${CFLAGS}"],[*"-pedantic"*],[CFLAGS="${CFLAGS} -Wno-pedantic"])
+	AS_CASE(["${CFLAGS}"],[*"-Werror"*],[CFLAGS="${CFLAGS} -Wno-error"])
+	AS_CASE(["${CFLAGS}"],[*"-flto"*],[CFLAGS="${CFLAGS} -ffat-lto-objects"])
+fi
 AC_PROG_LIBTOOL
+if ( test "${GCC}" = "yes" )
+then
+	CFLAGS="$CFLAGS_SAVED_NOPEDANTIC"
+fi
 
 dnl ${nut_with_dev}: any value except "yes" or "no" is treated as "auto".
 if test "${nut_with_dev}" != "no"; then
diff --git a/docs/developers.txt b/docs/developers.txt
index 63fb911b32..16c009e3c3 100644
--- a/docs/developers.txt
+++ b/docs/developers.txt
@@ -313,11 +313,46 @@ or access something outside their scope will throw a warning or even
 fail to compile in some cases.  This is what we want.
 
 
+Switch case fall-through
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+While C standards allow to write `switch` statements to "fall through"
+from handling one case into another, modern compilers frown upon that
+practice and spew warnings which complicate detecting real bugs in the
+code (and also looking back at some of the cases written decades ago,
+it is not trivial to state whether the fall-through was intentional or
+really is a bug).
+
+Compilers which detect such problem usually offer ways to decorate the
+code with comments or attributes to keep it quiet it in cases where the
+jump is intentional; also C++17 introduces special keywords for that in
+the standard. NUT aiming to be portable and independent of compilers as
+much as possible, prefers the arguably clearer and standards-based way
+of using `goto` into the next intended operation, even though it is a
+couple of lines away, e.g.:
+
+	int uppercase = 0;
+	switch (char_opt) {
+		case 'U':
+			uppercase = 1;
+			goto fallthrough_case_u_option;
+		case 'u':
+		fallthrough_case_u_option:
+			process_u_option(uppercase);
+			break;
+	}
+
+In trivial cases, like falling through to `default` which just returns,
+it may be clearer and more maintainable (adding other option cases in
+the future) to just `return same_result` in the code block that would
+fall through otherwise and avoid `goto` statements altogether.
+
 Spaghetti
 ~~~~~~~~~
 
-If you use a goto, expect us to drop it when our head stops spinning.
-It gives us flashbacks to the very old code we wrote.
+If you use a `goto` that jumps over long distances (see "Switch case
+fall-through" section above), expect us to drop it when our head stops
+spinning. It gives us flashbacks to the very old code we wrote.
 We've tried to clean up our act, and you should make the effort
 as well.
 
diff --git a/docs/nut.dict b/docs/nut.dict
index 6560129f3b..b311713596 100644
--- a/docs/nut.dict
+++ b/docs/nut.dict
@@ -1,4 +1,4 @@
-personal_ws-1.1 en 2514 utf-8
+personal_ws-1.1 en 2515 utf-8
 AAS
 ACFAIL
 ACFREQ
@@ -1542,6 +1542,7 @@ extendedhistory
 extradata
 fabula
 facto
+fallthrough
 fatalx
 faultsensitivity
 fc
diff --git a/include/common.h b/include/common.h
index 248dadd374..16b6d1127d 100644
--- a/include/common.h
+++ b/include/common.h
@@ -53,6 +53,33 @@ extern "C" {
 
 extern const char *UPS_VERSION;
 
+/* A somewhat portable way to mark unused variables to avoid warnings
+   (wherever we implement an API or ifdef large parts of codebase) per
+   https://stackoverflow.com/a/12891181/4715872
+ */
+/* Example: void foo(int NUT_UNUSED(bar)) { ... } */
+#ifdef __GNUC__
+#  define NUT_UNUSED(x) NUT_UNUSED_ ## x __attribute__((__unused__))
+#else
+#  define NUT_UNUSED(x) NUT_UNUSED_ ## x
+#endif
+
+/* Example: static void NUT_UNUSED_FUNCTION(foo)(int bar) { ... } */
+#ifdef __GNUC__
+#  define NUT_UNUSED_FUNCTION(x) __attribute__((__unused__)) NUT_UNUSED_ ## x
+#else
+#  define NUT_UNUSED_FUNCTION(x) NUT_UNUSED_ ## x
+#endif
+
+/* Use in code to notify the developers and quiesce the compiler that
+ * (for this codepath) the argument or variable is unused intentionally.
+ * void f(int x) {
+ *   NUT_UNUSED_VARIABLE(x);
+ *   ...
+ * }
+ */
+#define NUT_UNUSED_VARIABLE(x) (void)(x)
+
 /** @brief Default timeout (in seconds) for network operations, as used by `upsclient` and `nut-scanner`. */
 #define DEFAULT_NETWORK_TIMEOUT		5