Turn some warnings into errors

Make warnings (when available) related to common memory-related issues
into errors to harden the source and decrease chance of errors.

Change-Id: Ied9c950dafa65f324cf31298b13b590f56139700

debian/control

@@ -4,6 +4,7 @@ Section: net
 Priority: optional
 Build-Depends: debhelper (>= 9),
                autotools-dev,
+               autoconf-archive,
                pkg-config,
                libgtp0-dev,
                libosmocore-dev,

openbsc/configure.ac

@@ -140,6 +140,14 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([char foo;])],
 CFLAGS="$saved_CFLAGS"
 AC_SUBST(SYMBOL_VISIBILITY)
 
+# FIXME: use CC_CHECK_CFLAG_APPEND([-Werror=implicit])
+AX_CHECK_COMPILE_FLAG([-Werror=implicit], [CFLAGS="$CFLAGS -Werror=implicit"])
+AX_CHECK_COMPILE_FLAG([-Werror=maybe-uninitialized], [CFLAGS="$CFLAGS -Werror=maybe-uninitialized"])
+AX_CHECK_COMPILE_FLAG([-Werror=memset-transposed-args], [CFLAGS="$CFLAGS -Werror=memset-transposed-args"])
+AX_CHECK_COMPILE_FLAG([-Werror=null-dereference], [CFLAGS="$CFLAGS -Werror=null-dereference"])
+AX_CHECK_COMPILE_FLAG([-Werror=sizeof-array-argument], [CFLAGS="$CFLAGS -Werror=sizeof-array-argument"])
+AX_CHECK_COMPILE_FLAG([-Werror=sizeof-pointer-memaccess], [CFLAGS="$CFLAGS -Werror=sizeof-pointer-memaccess"])
+
 # Coverage build taken from WebKit's configure.in
 AC_MSG_CHECKING([whether to enable code coverage support])
 AC_ARG_ENABLE(coverage,