Centralize C++ version in Makefiles (#2713)

.github/workflows/ci.yml

@@ -143,7 +143,7 @@ jobs:
       - name: Build
         run: |
           ./autogen.sh
-          PKG_CONFIG_PATH=/usr/local/opt/curl/lib/pkgconfig:/usr/local/opt/openssl/lib/pkgconfig ./configure CXXFLAGS='-std=c++14'
+          PKG_CONFIG_PATH=/usr/local/opt/curl/lib/pkgconfig:/usr/local/opt/openssl/lib/pkgconfig ./configure
           make --jobs=$(sysctl -n hw.ncpu)
 
       - name: Cppcheck

Makefile.am

@@ -38,7 +38,7 @@ clang-tidy:
 cppcheck:
 	cppcheck --quiet --error-exitcode=1 \
             --inline-suppr \
-            --std=c++14 \
+            --std=@CPP_VERSION@ \
             --xml \
             -D HAVE_ATTR_XATTR_H \
             -D HAVE_SYS_EXTATTR_H \

configure.ac

@@ -34,7 +34,10 @@ AC_CHECK_HEADERS([attr/xattr.h])
 AC_CHECK_HEADERS([sys/extattr.h])
 AC_CHECK_FUNCS([fallocate])
 
-CXXFLAGS="-Wall -fno-exceptions -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=3 -std=c++14 $CXXFLAGS"
+CPP_VERSION=c++14
+AC_SUBST([CPP_VERSION])
+
+CXXFLAGS="-Wall -fno-exceptions -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=3 -std=$CPP_VERSION $CXXFLAGS"
 
 dnl ----------------------------------------------
 dnl For macOS

src/Makefile.am

@@ -103,7 +103,7 @@ TESTS = \
     test_string_util
 
 clang-tidy:
-	clang-tidy -extra-arg-before=-xc++ -extra-arg=-std=c++14 \
+	clang-tidy -extra-arg-before=-xc++ -extra-arg=-std=@CPP_VERSION@ \
 		*.h $(s3fs_SOURCES) test_curl_util.cpp test_page_list.cpp test_string_util.cpp \
 		-- $(DEPS_CFLAGS) $(CPPFLAGS)
 

test/Makefile.am

@@ -43,7 +43,7 @@ truncate_read_file_SOURCES = truncate_read_file.cc
 cr_filename_SOURCES        = cr_filename.cc
 
 clang-tidy:
-	clang-tidy -extra-arg=-std=c++14 \
+	clang-tidy -extra-arg=-std=@CPP_VERSION@ \
     $(junk_data_SOURCES) \
     $(write_multiblock_SOURCES) \
     $(mknod_test_SOURCES) \