[v2,10/10] Add --enable-ubsan

diff --git a/gdb/NEWS b/gdb/NEWS
index 2669fa91a1..17751bb120 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -103,6 +103,14 @@  CSKY GNU/LINUX			csky*-*-linux
   ** The gdb.Progspace type has a new 'objfiles' method, which returns the list
      of objfiles associated to that program space.
 
+* Configure changes
+
+--enable-ubsan
+
+  Enable or disable the undefined behavior sanitizer.  Release
+  versions of gdb disable this by default, but development versions
+  enable it.  Enabling this can cause a performance penalty.
+
 *** Changes in GDB 8.2
 
 * The 'set disassembler-options' command now supports specifying options
diff --git a/gdb/README b/gdb/README
index 5881be23af..69ba0eb8df 100644
--- a/gdb/README
+++ b/gdb/README
@@ -538,6 +538,13 @@  more obscure GDB `configure' options are not listed here.
      the compiler, which will fail the compilation if the compiler
      outputs any warning messages.
 
+`--enable-ubsan'
+     Enable the GCC undefined behavior sanitizer.  By default this is
+     disabled in GDB releases, but enabled when building from git.
+     The undefined behavior sanitizer checks for C++ undefined
+     behavior.  It has a performance cost, so if you are looking at
+     GDB's performance, you should disable it.
+
 `configure' accepts other options, for compatibility with configuring
 other GNU tools recursively.
 
diff --git a/gdb/acinclude.m4 b/gdb/acinclude.m4
index 3c2d01015b..52ba3f9ed6 100644
--- a/gdb/acinclude.m4
+++ b/gdb/acinclude.m4
@@ -15,6 +15,9 @@  sinclude(transform.m4)
 # This gets AM_GDB_WARNINGS.
 sinclude(warning.m4)
 
+# AM_GDB_UBSAN
+sinclude(sanitize.m4)
+
 dnl gdb/configure.in uses BFD_NEED_DECLARATION, so get its definition.
 sinclude(../bfd/bfd.m4)
 
diff --git a/gdb/configure b/gdb/configure
index b7c4ff6f29..4436cc970f 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -886,6 +886,7 @@  with_system_gdbinit
 enable_werror
 enable_build_warnings
 enable_gdb_build_warnings
+enable_ubsan
 with_lzma
 with_liblzma_prefix
 with_tcl
@@ -1556,6 +1557,7 @@  Optional Features:
   --enable-gdb-build-warnings
                           enable GDB specific build-time compiler warnings if
                           gcc is used
+  --enable-ubsan          enable undefined behavior sanitizer (auto/yes/no)
   --enable-sim            link gdb with simulator
   --enable-gdbserver      automatically build gdbserver (yes/no/auto, default
                           is auto)
@@ -2448,6 +2450,52 @@  $as_echo "$ac_res" >&6; }
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
 
 } # ac_fn_c_check_decl
+
+# ac_fn_cxx_try_link LINENO
+# -------------------------
+# Try to link conftest.$ac_ext, and return whether this succeeded.
+ac_fn_cxx_try_link ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  rm -f conftest.$ac_objext conftest$ac_exeext
+  if { { ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+$as_echo "$ac_try_echo"; } >&5
+  (eval "$ac_link") 2>conftest.err
+  ac_status=$?
+  if test -s conftest.err; then
+    grep -v '^ *+' conftest.err >conftest.er1
+    cat conftest.er1 >&5
+    mv -f conftest.er1 conftest.err
+  fi
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } && {
+	 test -z "$ac_cxx_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext && {
+	 test "$cross_compiling" = yes ||
+	 test -x conftest$ac_exeext
+       }; then :
+  ac_retval=0
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	ac_retval=1
+fi
+  # Delete the IPA/IPO (Inter Procedural Analysis/Optimization) information
+  # created by the PGI compiler (conftest_ipa8_conftest.oo), as it would
+  # interfere with the next link command; also delete a directory that is
+  # left behind by Apple's compiler.  We do this before executing the actions.
+  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_cxx_try_link
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
@@ -15561,6 +15609,63 @@  ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+# Check whether --enable-ubsan was given.
+if test "${enable_ubsan+set}" = set; then :
+  enableval=$enable_ubsan;
+else
+  enable_ubsan=auto
+fi
+
+if test "x$enable_ubsan" = xauto; then
+  if $development; then
+    enable_ubsan=yes
+  fi
+fi
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+if test "x$enable_ubsan" = xyes; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether -fsanitize=undefined is accepted" >&5
+$as_echo_n "checking whether -fsanitize=undefined is accepted... " >&6; }
+  saved_CXXFLAGS="$CXXFLAGS"
+  CXXFLAGS="$CXXFLAGS -fsanitize=undefined -fno-sanitize-recover=undefined"
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  enable_ubsan=yes
+else
+  enable_ubsan=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+  CXXFLAGS="$saved_CXXFLAGS"
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $enable_ubsan" >&5
+$as_echo "$enable_ubsan" >&6; }
+  if test "x$enable_ubsan" = xyes; then
+    WARN_CFLAGS="$WARN_CFLAGS -fsanitize=undefined -fno-sanitize-recover=undefined"
+    CONFIG_LDFLAGS="$CONFIG_LDFLAGS -fsanitize=undefined"
+  fi
+fi
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+
 # In the Cygwin environment, we need some additional flags.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for cygwin" >&5
 $as_echo_n "checking for cygwin... " >&6; }
diff --git a/gdb/configure.ac b/gdb/configure.ac
index 7f6a4033c8..34bfda0907 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1838,6 +1838,7 @@  GDB_AC_WITH_DIR(SYSTEM_GDBINIT, system-gdbinit,
     [])
 
 AM_GDB_WARNINGS
+AM_GDB_UBSAN
 
 # In the Cygwin environment, we need some additional flags.
 AC_CACHE_CHECK([for cygwin], gdb_cv_os_cygwin,
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 49a2cdce9e..913ea21b6e 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35744,6 +35744,13 @@  compiler you are using.
 Treat compiler warnings as werrors.  It adds the @code{-Werror} flag
 to the compiler, which will fail the compilation if the compiler
 outputs any warning messages.
+
+@item --enable-ubsan
+Enable the GCC undefined behavior sanitizer.  By default this is
+disabled in @value{GDBN} releases, but enabled when building from git.
+The undefined behavior sanitizer checks for C@t{++} undefined
+behavior.  It has a performance cost, so if you are looking at
+@value{GDBN}'s performance, you should disable it.
 @end table
 
 @node System-wide configuration
diff --git a/gdb/sanitize.m4 b/gdb/sanitize.m4
new file mode 100644
index 0000000000..3e2207b466
--- /dev/null
+++ b/gdb/sanitize.m4
@@ -0,0 +1,46 @@ 
+dnl Autoconf configure script for GDB, the GNU debugger.
+dnl Copyright (C) 2018 Free Software Foundation, Inc.
+dnl
+dnl This file is part of GDB.
+dnl
+dnl This program is free software; you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 3 of the License, or
+dnl (at your option) any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+dnl GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+AC_DEFUN([AM_GDB_UBSAN],[
+AC_ARG_ENABLE(ubsan,
+  AS_HELP_STRING([--enable-ubsan],
+                 [enable undefined behavior sanitizer (auto/yes/no)]),
+  [],enable_ubsan=auto)
+if test "x$enable_ubsan" = xauto; then
+  if $development; then
+    enable_ubsan=yes
+  fi
+fi
+AC_LANG_PUSH([C++])
+if test "x$enable_ubsan" = xyes; then
+  AC_MSG_CHECKING(whether -fsanitize=undefined is accepted)
+  saved_CXXFLAGS="$CXXFLAGS"
+  CXXFLAGS="$CXXFLAGS -fsanitize=undefined -fno-sanitize-recover=undefined"
+  dnl A link check is required because it is possible to install gcc
+  dnl without libubsan, leading to link failures when compiling with
+  dnl -fsanitize=undefined.
+  AC_TRY_LINK([],[],enable_ubsan=yes,enable_ubsan=no)
+  CXXFLAGS="$saved_CXXFLAGS"
+  AC_MSG_RESULT($enable_ubsan)
+  if test "x$enable_ubsan" = xyes; then
+    WARN_CFLAGS="$WARN_CFLAGS -fsanitize=undefined -fno-sanitize-recover=undefined"
+    CONFIG_LDFLAGS="$CONFIG_LDFLAGS -fsanitize=undefined"
+  fi
+fi
+AC_LANG_POP([C++])
+])