Remove Werror from CXXFLAGS

As newer & stricter C++ compiler versions are released, users run into
issues when building and installing bmv2. While we should keep using
Werror when developing and running CI tests, the flag should probably
not be used by default. A new configure flags (`--enable-Werror`) can be
used to add `Werror` to `CXXFLAGS`. Users should use the configure flags
instead of adding `Werror` to `CXXFLAGS` themselves, as the project
includes some auto-generated sources.

CONTRIBUTING.md

@@ -0,0 +1,26 @@
+You can fork the repo and submit a pull request in Github. For more information
+send us an email ([email protected]).
+
+### Apache CLA
+
+All developers must sign the [P4.org](http://p4.org) CLA and return it to
+([email protected]) before making contributions. The CLA is available
+[here](http://p4.org/wp-content/uploads/2015/07/P4_Language_Consortium_Membership_Agreement.pdf).
+
+### Coding guidelines
+
+Any contribution to the C++ core code (in particular the [bm_sim](src/bm_sim)
+module) must respect the coding guidelines. We rely heavily on the [Google C++
+Style Guide](https://google.github.io/styleguide/cppguide.html), with some
+differences listed in this repository's
+[wiki](https://github.com/p4lang/behavioral-model/wiki/Coding-guidelines). Every
+submitted pull request will go through our Travis tests, which include running
+`cpplint.py` to ensure correct style and formatting.
+
+### Building locally
+
+We recommend that you build with a recent C++ compiler and with `-Werror` since
+our CI tests use this flag. In order to build with the same flags as the CI
+tester, please run `configure` with the following flags:
+
+    ./configure --with-pdfixed --with-pi --with-stress-tests --enable-debugger --enable-Werror

Dockerfile

@@ -45,8 +45,8 @@ RUN apt-get update && \
     apt-get update && \
     apt-get install -y --no-install-recommends $BM_DEPS $BM_RUNTIME_DEPS && \
     ./autogen.sh && \
-    if [ "$GCOV" != "" ]; then ./configure --with-pdfixed --with-stress-tests --enable-debugger --enable-coverage; fi && \
-    if [ "$GCOV" = "" ]; then ./configure --with-pdfixed --with-stress-tests --enable-debugger; fi && \
+    if [ "$GCOV" != "" ]; then ./configure --with-pdfixed --with-stress-tests --enable-debugger --enable-coverage --enable-Werror; fi && \
+    if [ "$GCOV" = "" ]; then ./configure --with-pdfixed --with-stress-tests --enable-debugger --enable-Werror; fi && \
     make && \
     make install-strip && \
     ldconfig && \

README.md

@@ -244,17 +244,4 @@ Please submit an issue with the appropriate label on
 
 ### How can I contribute ?
 
-You can fork the repo and submit a pull request in Github. For more information
-send us an email ([email protected]).
-
-All developers must sign the [P4.org](http://p4.org) CLA and return it to
-([email protected]) before making contributions. The CLA is available
-[here](http://p4.org/wp-content/uploads/2015/07/P4_Language_Consortium_Membership_Agreement.pdf).
-
-Any contribution to the C++ core code (in particular the [bm_sim](src/bm_sim)
-module) must respect the coding guidelines. We rely heavily on the [Google C++
-Style Guide](https://google.github.io/styleguide/cppguide.html), with some
-differences listed in this repository's
-[wiki](https://github.com/p4lang/behavioral-model/wiki/Coding-guidelines). Every
-submitted pull request will go through our Travis tests, which include running
-`cpplint.py` to ensure correct style and formatting.
+See [CONTRIBUTING.md](CONTRIBUTING.md).

configure.ac

@@ -108,6 +108,10 @@ AC_ARG_WITH([pi],
 
 AM_CONDITIONAL([COND_PI], [test "$want_pi" = yes])
 
+AC_ARG_ENABLE([Werror],
+    AS_HELP_STRING([--enable-Werror], [Make all compiler warnings fatal]),
+    [enable_Werror="$enableval"], [enable_Werror=no])
+
 # Checks for programs.
 AC_PROG_CXX
 AC_PROG_CC
@@ -215,9 +219,12 @@ AC_SUBST([AM_CPPFLAGS], ["$MY_CPPFLAGS \
                           -I\$(top_srcdir)/include \
                           -isystem\$(top_srcdir)/third_party/jsoncpp/include \
                           -isystem\$(top_srcdir)/third_party/spdlog"])
-
-AC_SUBST([AM_CXXFLAGS], ["$PTHREAD_CFLAGS -Wall -Werror -Wextra"])
 AC_SUBST([AM_CFLAGS], ["$PTHREAD_CFLAGS"])
+# Using ax_append_compile_flags requires copying 4 macro definitions from the
+# autoconf archive to m4/
+MY_CXXFLAGS="-Wall -Wextra"
+AS_IF([test "$enable_Werror" = "yes"], [MY_CXXFLAGS="$MY_CXXFLAGS -Werror"])
+AC_SUBST([AM_CXXFLAGS], ["$MY_CXXFLAGS $PTHREAD_CFLAGS"])
 
 # Checks for typedefs, structures, and compiler characteristics.
 # not supported by autoconf 2.68, add to m4/ ?

targets/simple_switch_grpc/Makefile.am

@@ -110,5 +110,7 @@ AM_CPPFLAGS += -Icpp_out -Igrpc_out \
 -I$(builddir)/cpp_out -I$(builddir)/grpc_out
 
 nodist_libbm_grpc_dataplane_la_SOURCES = $(proto_cpp_files) $(proto_grpc_files)
+# no warnings or Werror for auto-generated sources
+nodist_libbm_grpc_dataplane_la_CXXFLAGS =
 
 CLEANFILES = $(BUILT_SOURCES) proto_files.ts

targets/simple_switch_grpc/configure.ac

@@ -30,8 +30,17 @@ AC_TYPE_UINT32_T
 AC_TYPE_UINT64_T
 AC_TYPE_SIZE_T
 
+AC_ARG_ENABLE([Werror],
+    AS_HELP_STRING([--enable-Werror], [Make all compiler warnings fatal]),
+    [enable_Werror="$enableval"], [enable_Werror=no])
+
 AC_SUBST([AM_CPPFLAGS], ["$MY_CPPFLAGS"])
-AC_SUBST([AM_CFLAGS], ["$PTHREAD_CFLAGS -Wall -Werror -Wextra"])
+AC_SUBST([AM_CFLAGS], ["$PTHREAD_CFLAGS"])
+# Using ax_append_compile_flags requires copying 4 macro definitions from the
+# autoconf archive to m4/
+MY_CXXFLAGS="-Wall -Wextra"
+AS_IF([test "$enable_Werror" = "yes"], [MY_CXXFLAGS="$MY_CXXFLAGS -Werror"])
+AC_SUBST([AM_CXXFLAGS], ["$MY_CXXFLAGS $PTHREAD_CFLAGS"])
 
 PKG_CHECK_MODULES([PROTOBUF], [protobuf >= 3.0.0])
 AC_SUBST([PROTOBUF_CFLAGS])