Merge #12686: Add -ftrapv to CFLAGS and CXXFLAGS when --enable-debug is used. Enable -ftrapv in Travis.

98d842cb52 travis: Build with --enable-debug (x86_64-unknown-linux-gnu) (practicalswift)
94e52d13db Add -ftrapv to DEBUG_CXXFLAGS when --enable-debug is used (practicalswift)

Pull request description:

  By generating a trap for signed overflow on addition, subtraction, multiplication operations in the Travis testing we are more likely to identify problematic code prior to merging it.

Tree-SHA512: 47712da53b4ff451b8f22f16ddc3b53100a09060a3b04cda4b8fbbb74e6f666fc07a9cc7abc64cacb87a0aa3f62dc8e3c91a1a0ed12bf82bb2a5624a5d104389

.travis.yml

@@ -34,7 +34,7 @@ env:
 # 32-bit + dash
     - HOST=i686-pc-linux-gnu PACKAGES="g++-multilib python3-zmq" DEP_OPTS="NO_QT=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --enable-glibc-back-compat --enable-reduce-exports LDFLAGS=-static-libstdc++" CONFIG_SHELL="/bin/dash"
 # x86_64 Linux (uses qt5 dev package instead of depends Qt to speed up build and avoid timeout)
-    - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools protobuf-compiler libdbus-1-dev libharfbuzz-dev libprotobuf-dev" DEP_OPTS="NO_QT=1 NO_UPNP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports CPPFLAGS=-DDEBUG_LOCKORDER"
+    - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools protobuf-compiler libdbus-1-dev libharfbuzz-dev libprotobuf-dev" DEP_OPTS="NO_QT=1 NO_UPNP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports --enable-debug"
 # x86_64 Linux (Qt5 & system libs)
     - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools libssl1.0-dev libevent-dev bsdmainutils libboost-system-dev libboost-filesystem-dev libboost-chrono-dev libboost-program-options-dev libboost-test-dev libboost-thread-dev libdb5.3++-dev libminiupnpc-dev libzmq3-dev libprotobuf-dev protobuf-compiler libqrencode-dev" NO_DEPENDS=1 RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --enable-glibc-back-compat --enable-reduce-exports --with-gui=qt5 CPPFLAGS=-DDEBUG_LOCKORDER"
 # x86_64 Linux, No wallet

configure.ac

@@ -263,6 +263,7 @@ if test "x$enable_debug" = xyes; then
 
   AX_CHECK_PREPROC_FLAG([-DDEBUG],[[DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -DDEBUG"]],,[[$CXXFLAG_WERROR]])
   AX_CHECK_PREPROC_FLAG([-DDEBUG_LOCKORDER],[[DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -DDEBUG_LOCKORDER"]],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-ftrapv],[DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -ftrapv"],,[[$CXXFLAG_WERROR]])
 fi
 
 if test x$use_sanitizers != x; then