We now require C++14.

I'm tired of working around missing features that were added in C++14. It's four years old now, compilers should support it.

c++/CMakeLists.txt

@@ -7,12 +7,12 @@ set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 include(CheckIncludeFileCXX)
 include(GNUInstallDirs)
 if(MSVC)
-  check_include_file_cxx(initializer_list HAS_CXX11)
+  check_include_file_cxx(initializer_list HAS_CXX14)
 else()
-  check_include_file_cxx(initializer_list HAS_CXX11 "-std=gnu++0x")
+  check_include_file_cxx(initializer_list HAS_CXX14 "-std=gnu++1y")
 endif()
-if(NOT HAS_CXX11)
-  message(SEND_ERROR "Requires a C++11 compiler and standard library.")
+if(NOT HAS_CXX14)
+  message(SEND_ERROR "Requires a C++14 compiler and standard library.")
 endif()
 
 # these arguments are passed to all install(TARGETS) calls
@@ -66,7 +66,7 @@ else()
   add_compile_options(-Wall -Wextra -Wno-strict-aliasing -Wno-sign-compare -Wno-unused-parameter)
 
   if(DEFINED CMAKE_CXX_EXTENSIONS AND NOT CMAKE_CXX_EXTENSIONS)
-    message(SEND_ERROR "Cap'n Proto requires compiler-specific extensions (e.g., -std=gnu++11). Please leave CMAKE_CXX_EXTENSIONS undefined or ON.")
+    message(SEND_ERROR "Cap'n Proto requires compiler-specific extensions (e.g., -std=gnu++14). Please leave CMAKE_CXX_EXTENSIONS undefined or ON.")
   endif()
 
   if (NOT ANDROID)

c++/Makefile.ekam

@@ -16,19 +16,19 @@ all:
 	echo "You probably accidentally told Eclipse to build.  Stopping."
 
 once:
-	CXXFLAGS="$(EXTRA_FLAG) -std=c++11 -O2 -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6
+	CXXFLAGS="$(EXTRA_FLAG) -std=c++14 -O2 -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6
 
 continuous:
-	CXXFLAGS="$(EXTRA_FLAG) -std=c++11 -g -DCAPNP_DEBUG_TYPES=1 -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
+	CXXFLAGS="$(EXTRA_FLAG) -std=c++14 -g -DCAPNP_DEBUG_TYPES=1 -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
 
 continuous-opt:
-	CXXFLAGS="$(EXTRA_FLAG) -std=c++11 -O2 -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
+	CXXFLAGS="$(EXTRA_FLAG) -std=c++14 -O2 -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
 
 continuous-opt3:
-	CXXFLAGS="$(EXTRA_FLAG) -std=c++11 -O3 -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
+	CXXFLAGS="$(EXTRA_FLAG) -std=c++14 -O3 -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
 
 continuous-opts:
-	CXXFLAGS="$(EXTRA_FLAG) -std=c++11 -Os -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
+	CXXFLAGS="$(EXTRA_FLAG) -std=c++14 -Os -DNDEBUG -Wall" LIBS='-lz -pthread' $(EKAM) -j6 -c -n :51315
 
 clean:
 	rm -rf bin lib tmp

c++/cmake/CapnProtoTargets.cmake

@@ -136,7 +136,7 @@ function(_capnp_import_pkg_config_target target)
   set_target_properties(CapnProto::${target} PROPERTIES
     ${imported_soname_property}
     IMPORTED_LOCATION "${target_location}"
-    INTERFACE_COMPILE_FEATURES "cxx_constexpr"
+    INTERFACE_COMPILE_FEATURES "cxx_std_14"
     INTERFACE_COMPILE_OPTIONS "${${target}_CFLAGS_OTHER}"
     INTERFACE_INCLUDE_DIRECTORIES "${${target}_INCLUDE_DIRS}"
 

c++/configure.ac

@@ -50,7 +50,7 @@ AC_ARG_ENABLE([reflection], [
 AC_PROG_CC
 AC_PROG_CXX
 AC_LANG([C++])
-AX_CXX_COMPILE_STDCXX_11
+AX_CXX_COMPILE_STDCXX_14
 
 AS_CASE("${host_os}", *mingw*, [
     # We don't use pthreads on MinGW.

c++/m4/ax_cxx_compile_stdcxx_11.m4 → c++/m4/ax_cxx_compile_stdcxx_14.m4

 # ============================================================================
 #  http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
 #  Additionally modified to detect -stdlib by Kenton Varda.
+#  Further modified for C++14 by Kenton Varda.
 # ============================================================================
 #
 # SYNOPSIS
 #
-#   AX_CXX_COMPILE_STDCXX_11([ext|noext])
+#   AX_CXX_COMPILE_STDCXX_14([ext|noext])
 #
 # DESCRIPTION
 #
-#   Check for baseline language coverage in the compiler for the C++11
+#   Check for baseline language coverage in the compiler for the C++14
 #   standard; if necessary, add switches to CXXFLAGS to enable support.
-#   Errors out if no mode that supports C++11 baseline syntax can be found.
+#   Errors out if no mode that supports C++14 baseline syntax can be found.
 #   The argument, if specified, indicates whether you insist on an extended
-#   mode (e.g. -std=gnu++11) or a strict conformance mode (e.g. -std=c++11).
+#   mode (e.g. -std=gnu++14) or a strict conformance mode (e.g. -std=c++14).
 #   If neither is specified, you get whatever works, with preference for an
 #   extended mode.
 #
@@ -42,7 +43,7 @@
 
 #serial 1
 
-m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [
+m4_define([_AX_CXX_COMPILE_STDCXX_14_testbody], [[
   template <typename T>
   struct check
   {
@@ -78,7 +79,18 @@ m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [
   #include <type_traits>
   #endif
   #endif
-])
+
+  // C++14 stuff
+  auto deduceReturnType(int i) { return i; }
+
+  auto genericLambda = [](auto x, auto y) { return x + y; };
+  auto captureExpressions = [x = 123]() { return x; };
+
+  // Avoid unused variable warnings.
+  int foo() {
+    return genericLambda(1, 2) + captureExpressions();
+  }
+]])
 
 m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody_lib], [
   #include <initializer_list>
@@ -87,31 +99,31 @@ m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody_lib], [
   #include <thread>
 ])
 
-AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
+AC_DEFUN([AX_CXX_COMPILE_STDCXX_14], [dnl
   m4_if([$1], [], [],
         [$1], [ext], [],
         [$1], [noext], [],
-        [m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_11])])dnl
+        [m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_14])])dnl
   AC_LANG_ASSERT([C++])dnl
   ac_success=no
-  AC_CACHE_CHECK(whether $CXX supports C++11 features by default,
-  ax_cv_cxx_compile_cxx11,
-  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
-    [ax_cv_cxx_compile_cxx11=yes],
-    [ax_cv_cxx_compile_cxx11=no])])
-  if test x$ax_cv_cxx_compile_cxx11 = xyes; then
+  AC_CACHE_CHECK(whether $CXX supports C++14 features by default,
+  ax_cv_cxx_compile_cxx14,
+  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
+    [ax_cv_cxx_compile_cxx14=yes],
+    [ax_cv_cxx_compile_cxx14=no])])
+  if test x$ax_cv_cxx_compile_cxx14 = xyes; then
     ac_success=yes
   fi
 
   m4_if([$1], [noext], [], [dnl
   if test x$ac_success = xno; then
-    for switch in -std=gnu++11 -std=gnu++0x; do
-      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
-      AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
+    for switch in -std=gnu++14 -std=gnu++1y; do
+      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
+      AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
                      $cachevar,
         [ac_save_CXX="$CXX"
          CXX="$CXX $switch"
-         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
+         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
           [eval $cachevar=yes],
           [eval $cachevar=no])
          CXX="$ac_save_CXX"])
@@ -125,13 +137,13 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
 
   m4_if([$1], [ext], [], [dnl
   if test x$ac_success = xno; then
-    for switch in -std=c++11 -std=c++0x; do
-      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
-      AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
+    for switch in -std=c++14 -std=c++1y; do
+      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx14_$switch])
+      AC_CACHE_CHECK(whether $CXX supports C++14 features with $switch,
                      $cachevar,
         [ac_save_CXX="$CXX"
          CXX="$CXX $switch"
-         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
+         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_14_testbody])],
           [eval $cachevar=yes],
           [eval $cachevar=no])
          CXX="$ac_save_CXX"])
@@ -144,7 +156,7 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
   fi])
 
   if test x$ac_success = xno; then
-    AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.])
+    AC_MSG_ERROR([*** A compiler with support for C++14 language features is required.])
   else
     ac_success=no
     AC_CACHE_CHECK(whether $CXX supports C++11 library features by default,

c++/samples/addressbook.c++

@@ -23,12 +23,12 @@
 //
 // If Cap'n Proto is installed, build the sample like:
 //   capnp compile -oc++ addressbook.capnp
-//   c++ -std=c++11 -Wall addressbook.c++ addressbook.capnp.c++ `pkg-config --cflags --libs capnp` -o addressbook
+//   c++ -std=c++14 -Wall addressbook.c++ addressbook.capnp.c++ `pkg-config --cflags --libs capnp` -o addressbook
 //
 // If Cap'n Proto is not installed, but the source is located at $SRC and has been
 // compiled in $BUILD (often both are simply ".." from here), you can do:
 //   $BUILD/capnp compile -I$SRC/src -o$BUILD/capnpc-c++ addressbook.capnp
-//   c++ -std=c++11 -Wall addressbook.c++ addressbook.capnp.c++ -I$SRC/src -L$BUILD/.libs -lcapnp -lkj -o addressbook
+//   c++ -std=c++14 -Wall addressbook.c++ addressbook.capnp.c++ -I$SRC/src -L$BUILD/.libs -lcapnp -lkj -o addressbook
 //
 // Run like:
 //   ./addressbook write | ./addressbook read

c++/samples/test.sh

@@ -6,16 +6,16 @@
 set -exuo pipefail
 
 capnpc -oc++ addressbook.capnp
-c++ -std=c++11 -Wall addressbook.c++ addressbook.capnp.c++ \
+c++ -std=c++14 -Wall addressbook.c++ addressbook.capnp.c++ \
     $(pkg-config --cflags --libs capnp) -o addressbook
 ./addressbook write | ./addressbook read
 ./addressbook dwrite | ./addressbook dread
 rm addressbook addressbook.capnp.c++ addressbook.capnp.h
 
 capnpc -oc++ calculator.capnp
-c++ -std=c++11 -Wall calculator-client.c++ calculator.capnp.c++ \
+c++ -std=c++14 -Wall calculator-client.c++ calculator.capnp.c++ \
     $(pkg-config --cflags --libs capnp-rpc) -o calculator-client
-c++ -std=c++11 -Wall calculator-server.c++ calculator.capnp.c++ \
+c++ -std=c++14 -Wall calculator-server.c++ calculator.capnp.c++ \
     $(pkg-config --cflags --libs capnp-rpc) -o calculator-server
 rm -f /tmp/capnp-calculator-example-$$
 ./calculator-server unix:/tmp/capnp-calculator-example-$$ &

c++/src/kj/CMakeLists.txt

@@ -66,8 +66,7 @@ set(kj-std_headers
 )
 add_library(kj ${kj_sources})
 add_library(CapnProto::kj ALIAS kj)
-target_compile_features(kj PUBLIC cxx_constexpr)
-# Requiring the cxx_std_11 metafeature would be preferable, but that doesn't exist until CMake 3.8.
+target_compile_features(kj PUBLIC cxx_std_14)
 
 if(UNIX AND NOT ANDROID)
   target_link_libraries(kj PUBLIC pthread)

c++/src/kj/common.h

@@ -30,33 +30,26 @@
 #endif
 
 #ifndef KJ_NO_COMPILER_CHECK
-#if __cplusplus < 201103L && !__CDT_PARSER__ && !_MSC_VER
-  #error "This code requires C++11. Either your compiler does not support it or it is not enabled."
+#if __cplusplus < 201402L && !__CDT_PARSER__ && !_MSC_VER
+  #error "This code requires C++14. Either your compiler does not support it or it is not enabled."
   #ifdef __GNUC__
     // Compiler claims compatibility with GCC, so presumably supports -std.
-    #error "Pass -std=c++11 on the compiler command line to enable C++11."
+    #error "Pass -std=c++14 on the compiler command line to enable C++14."
   #endif
 #endif
 
 #ifdef __GNUC__
   #if __clang__
-    #if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 2)
-      #warning "This library requires at least Clang 3.2."
-    #elif defined(__apple_build_version__) && __apple_build_version__ <= 4250028
-      #warning "This library requires at least Clang 3.2.  XCode 4.6's Clang, which claims to be "\
-               "version 4.2 (wat?), is actually built from some random SVN revision between 3.1 "\
-               "and 3.2.  Unfortunately, it is insufficient for compiling this library.  You can "\
-               "download the real Clang 3.2 (or newer) from the Clang web site.  Step-by-step "\
-               "instructions can be found in Cap'n Proto's documentation: "\
-               "http://kentonv.github.io/capnproto/install.html#clang_32_on_mac_osx"
-    #elif __cplusplus >= 201103L && !__has_include(<initializer_list>)
-      #warning "Your compiler supports C++11 but your C++ standard library does not.  If your "\
+    #if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 4)
+      #warning "This library requires at least Clang 3.4."
+    #elif __cplusplus >= 201402L && !__has_include(<initializer_list>)
+      #warning "Your compiler supports C++14 but your C++ standard library does not.  If your "\
                "system has libc++ installed (as should be the case on e.g. Mac OSX), try adding "\
                "-stdlib=libc++ to your CXXFLAGS."
     #endif
   #else
-    #if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 7)
-      #warning "This library requires at least GCC 4.7."
+    #if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 9)
+      #warning "This library requires at least GCC 4.9."
     #endif
   #endif
 #elif defined(_MSC_VER)
@@ -64,8 +57,8 @@
     #error "You need Visual Studio 2017 or better to compile this code."
   #endif
 #else
-  #warning "I don't recognize your compiler.  As of this writing, Clang and GCC are the only "\
-           "known compilers with enough C++11 support for this library.  "\
+  #warning "I don't recognize your compiler. As of this writing, Clang, GCC, and Visual Studio "\
+           "are the only known compilers with enough C++14 support for this library. "\
            "#define KJ_NO_COMPILER_CHECK to make this warning go away."
 #endif
 #endif

super-test.sh

@@ -362,7 +362,7 @@ doit make -j$PARALLEL check
 if [ $IS_CLANG = no ]; then
   # Verify that generated code compiles with pedantic warnings.  Make sure to treat capnp headers
   # as system headers so warnings in them are ignored.
-  doit ${CXX:-g++} -isystem src -std=c++11 -fno-permissive -pedantic -Wall -Wextra -Werror \
+  doit ${CXX:-g++} -isystem src -std=c++1y -fno-permissive -pedantic -Wall -Wextra -Werror \
       -c src/capnp/test.capnp.c++ -o /dev/null
 fi
 
@@ -378,13 +378,13 @@ test "x$(which capnpc-c++)" = "x$STAGING/bin/capnpc-c++"
 cd samples
 
 doit capnp compile -oc++ addressbook.capnp -I"$STAGING"/include --no-standard-import
-doit ${CXX:-g++} -std=c++11 addressbook.c++ addressbook.capnp.c++ -o addressbook \
+doit ${CXX:-g++} -std=c++1y addressbook.c++ addressbook.capnp.c++ -o addressbook \
     $CXXFLAGS $(pkg-config --cflags --libs capnp)
 
 doit capnp compile -oc++ calculator.capnp -I"$STAGING"/include --no-standard-import
-doit ${CXX:-g++} -std=c++11 calculator-client.c++ calculator.capnp.c++ -o calculator-client \
+doit ${CXX:-g++} -std=c++1y calculator-client.c++ calculator.capnp.c++ -o calculator-client \
     $CXXFLAGS $(pkg-config --cflags --libs capnp-rpc)
-doit ${CXX:-g++} -std=c++11 calculator-server.c++ calculator.capnp.c++ -o calculator-server \
+doit ${CXX:-g++} -std=c++1y calculator-server.c++ calculator.capnp.c++ -o calculator-server \
     $CXXFLAGS $(pkg-config --cflags --libs capnp-rpc)
 
 test_samples