diff --git a/.github/workflows/compilation.yml b/.github/workflows/compilation.yml
index fe372f45..6ff0a397 100644
--- a/.github/workflows/compilation.yml
+++ b/.github/workflows/compilation.yml
@@ -20,8 +20,10 @@ jobs:
           set -x
           $CXX --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall -fdiagnostics-color=always"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_gcc8:
     name: "GCC 8 (ubuntu-18.04)"
@@ -39,8 +41,10 @@ jobs:
           set -x
           $CXX --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall -fdiagnostics-color=always"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_ubuntu:
     name: "GCC"
@@ -58,8 +62,10 @@ jobs:
           set -x
           g++ --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall -fdiagnostics-color=always"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_clang:
     name: "Clang 6 (ubuntu-18.04)"
@@ -77,8 +83,10 @@ jobs:
           set -x
           $CXX --version
           ./autogen.sh
-          ./configure
-          make -j "$(nproc)"
+          ./configure CXXFLAGS="-Wall"
+          make -j "$(nproc)" |& tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
 
   build_macos:
     name: "Clang (macOS-10.14)"
@@ -93,5 +101,7 @@ jobs:
           set -x
           clang++ --version
           ./autogen.sh
-          ./configure
-          make -j "$(sysctl -n hw.physicalcpu)"
+          ./configure CXXFLAGS="-Wall"
+          make -j "$(sysctl -n hw.physicalcpu)" 2>&1 | tee build.log
+      - name: Summarize warnings
+        run: python3 ./scripts/count-warnings.py build.log
diff --git a/scripts/count-warnings.py b/scripts/count-warnings.py
new file mode 100644
index 00000000..54aa06a8
--- /dev/null
+++ b/scripts/count-warnings.py
@@ -0,0 +1,88 @@
+#!/usr/bin/python3
+
+# Copyright (c) 2019 Patryk Obara
+
+# This script counts and all warnings and prints a summary.
+#
+# Usage: ./count-warnings.py build.log
+# Usage: cat "*.log" | ./count-warnings.py -
+#
+# note: new compilers include additional flag -fdiagnostics-format=[text|json],
+# which could be used instead of parsing using regex, but we want to preserve
+# human-readable output in standard log.
+
+# pylint: disable=invalid-name
+# pylint: disable=missing-docstring
+
+import os
+import re
+import sys
+
+# Maximum allowed number of warnings; if build will include more warnings,
+# then script will return with status 1. Simply change this line if you
+# want to set a different limit.
+#
+MAX_WARNINGS = 357
+
+# For recognizing warnings in GCC format in stderr:
+#
+WARNING_PATTERN = re.compile(r'([^:]+):(\d+):\d+: warning: .* \[-W(.+)\]')
+#                               ~~~~~   ~~~  ~~~           ~~      ~~
+#                               ↑       ↑    ↑             ↑       ↑
+#                               file    line column        message type
+
+# For removing color when GCC is invoked with -fdiagnostics-color=always
+#
+ANSI_COLOR_PATTERN = re.compile(r'\x1b\[[0-9;]*[mGKH]')
+
+
+def remove_colors(line):
+    return re.sub(ANSI_COLOR_PATTERN, '', line)
+
+
+def count_warning(line, warning_types):
+    line = remove_colors(line)
+    match = WARNING_PATTERN.match(line)
+    if not match:
+        return 0
+    # file = match.group(1)
+    # line = match.group(2)
+    wtype = match.group(3)
+    count = warning_types.get(wtype) or 0
+    warning_types[wtype] = count + 1
+    return 1
+
+
+def get_input_lines(name):
+    if name == '-':
+        return sys.stdin.readlines()
+    if not os.path.isfile(name):
+        print('{}: no such file.'.format(name))
+        sys.exit(2)
+    with open(name, 'r') as logs:
+        return logs.readlines()
+
+
+def print_summary(warning_types):
+    print("Warnings grouped by type:\n")
+    summary = list(warning_types.items())
+    for warning, count in sorted(summary, key=lambda x: -x[1]):
+        print('  {:28s}: {}'.format(warning, count))
+    print()
+
+
+def main():
+    total = 0
+    warning_types = {}
+    for line in get_input_lines(sys.argv[1]):
+        total += count_warning(line, warning_types)
+    if warning_types:
+        print_summary(warning_types)
+    print('Total: {} warnings\n'.format(total))
+    if total > MAX_WARNINGS:
+        print('Error: upper limit of warnings is', MAX_WARNINGS)
+        sys.exit(1)
+
+
+if __name__ == '__main__':
+    main()