diff --git a/NEWS b/NEWS
index 95f40427..201fcab4 100644
--- a/NEWS
+++ b/NEWS
@@ -40,6 +40,8 @@ Changes:
   • Clarify documentation (fd.o #35182, Simon McVittie)
   • Clean up minor dead code and some incorrect error handling
     (fd.o #33128, fd.o #29881; Simon McVittie)
+  • Check that compiler options are supported before using them (fd.o #19681,
+    Simon McVittie)
   • Windows:
     • Remove obsolete workaround for winioctl.h (fd.o #35083, Ralf Habacker)
 
diff --git a/configure.ac b/configure.ac
index 3022f403..b51b842e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -382,7 +382,7 @@ dnl **********************************
 dnl we currently check for all three va_copy possibilities, so we get
 dnl all results in config.log for bug reports.
 AC_CACHE_CHECK([for an implementation of va_copy()],dbus_cv_va_copy,[
-	AC_LINK_IFELSE([#include <stdarg.h>
+	AC_LINK_IFELSE([AC_LANG_SOURCE([#include <stdarg.h>
 #include <stdlib.h>
 	static void f (int i, ...) {
 	va_list args1, args2;
@@ -395,12 +395,12 @@ AC_CACHE_CHECK([for an implementation of va_copy()],dbus_cv_va_copy,[
 	int main() {
 	  f (0, 42);
 	  return 0;
-	}],
+	}])],
 	[dbus_cv_va_copy=yes],
 	[dbus_cv_va_copy=no])
 ])
 AC_CACHE_CHECK([for an implementation of __va_copy()],dbus_cv___va_copy,[
-	AC_LINK_IFELSE([#include <stdarg.h>
+	AC_LINK_IFELSE([AC_LANG_SOURCE([#include <stdarg.h>
 #include <stdlib.h>
 	static void f (int i, ...) {
 	va_list args1, args2;
@@ -413,7 +413,7 @@ AC_CACHE_CHECK([for an implementation of __va_copy()],dbus_cv___va_copy,[
 	int main() {
 	  f (0, 42);
 	  return 0;
-	}],
+	}])],
 	[dbus_cv___va_copy=yes],
 	[dbus_cv___va_copy=no])
 ])
@@ -466,8 +466,8 @@ fi
 
 AC_CACHE_CHECK([whether $CC knows __sync_sub_and_fetch()],
   dbus_cv_sync_sub_and_fetch,
-  [AC_LINK_IFELSE(
-     AC_LANG_PROGRAM([], [[int a = 4; int b = __sync_sub_and_fetch(&a, 4); exit(b); ]]),
+  [AC_LINK_IFELSE([
+     AC_LANG_PROGRAM([[]], [[int a = 4; int b = __sync_sub_and_fetch(&a, 4); exit(b); ]])],
      [dbus_cv_sync_sub_and_fetch=yes],
      [dbus_cv_sync_sub_and_fetch=no])
   ])
@@ -1142,135 +1142,53 @@ cc_supports_flag() {
   test "x$rc" = xyes
 }
 
-# Don't bother with -Werror on Windows for now, too many warnings
-if test x$dbus_win != xyes -a x$dbus_cygwin != xyes -a x$USE_MAINTAINER_MODE = xyes; then
-  if cc_supports_flag "-Werror"; then
-    CFLAGS="$CFLAGS -Werror"
+TP_COMPILER_WARNINGS([WARNING_CFLAGS],
+  dnl Use -Werror by default if:
+  dnl - we're not on Windows (too many warnings), and
+  dnl - we're in maintainer mode (a D-Bus developer, not a distro or end-user)
+  dnl Override with --enable-Werror or --disable-Werror
+  [test x$dbus_win != xyes -a x$dbus_cygwin != xyes -a x$USE_MAINTAINER_MODE = xyes],
+
+  dnl enable these warnings if possible:
+  [all \
+   char-subscripts \
+   missing-declarations \
+   missing-prototypes \
+   nested-externs \
+   pointer-arith \
+   cast-align \
+   no-address \
+   float-equal \
+   declaration-after-statement \
+  ],
+
+  dnl disable these warnings if possible, make them non-fatal if possible,
+  dnl and don't enable -Werror unless we succeeded:
+  dnl (unused is by design, sign-compare and pointer-sign are fd.o #17433)
+  [unused \
+   sign-compare \
+   pointer-sign \
+  ])
+
+if test "x$GCC" = "xyes"; then
+  # We're treating -fno-common like a warning: it makes the linker more
+  # strict, because on some systems the linker is *always* this strict
+  TP_ADD_COMPILER_FLAG([WARNING_CFLAGS], [-fno-common])
+
+  # http://bugs.freedesktop.org/show_bug.cgi?id=10599
+  TP_ADD_COMPILER_FLAG([WARNING_CFLAGS], [-fno-strict-aliasing])
+
+  if test "x$enable_ansi" = "xyes"; then
+    TP_ADD_COMPILER_FLAG([WARNING_CFLAGS],
+      [-ansi -D_POSIX_C_SOURCE=199309L -D_BSD_SOURCE -pedantic])
   fi
 fi
 
-dnl This whole "if" block is in m4 quotes ([]) because it uses them
-dnl for character ranges internally. m4 macros cannot be used inside this
-dnl block.
-[if test "x$GCC" = "xyes"; then
-  case " $CFLAGS " in
-  *[\ \	]-Wall[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wall" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wchar-subscripts[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wchar-subscripts" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wmissing-declarations[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wmissing-declarations" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wmissing-prototypes[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wmissing-prototypes" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wnested-externs[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wnested-externs" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wpointer-arith[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wpointer-arith" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wcast-align[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wcast-align" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wno-address[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wno-address" ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wfloat-equal[\ \	]*) ;;
-  *) if cc_supports_flag -Wfloat-equal; then
-        CFLAGS="$CFLAGS -Wfloat-equal"
-     fi
-     ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-Wdeclaration-after-statement[\ \	]*) ;;
-  *) if cc_supports_flag -Wdeclaration-after-statement; then
-        CFLAGS="$CFLAGS -Wdeclaration-after-statement"
-     fi
-     ;;
-  esac
-
-  case " $CFLAGS " in
-  *[\ \	]-fno-common[\ \	]*) ;;
-  *) if cc_supports_flag -fno-common; then
-        CFLAGS="$CFLAGS -fno-common"
-     fi
-     ;;
-  esac
-
-  ### Disabled warnings, and compiler flag overrides
-
-  # Let's just ignore unused for now
-  case " $CFLAGS " in
-  *[\ \	]-Wno-unused[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wno-unused" ;;
-  esac
-
-  # This group is for warnings we currently don't pass.
-  # We would like to, however.  Please fix.
-
-  # http://bugs.freedesktop.org/show_bug.cgi?id=17433
-  case " $CFLAGS " in
-  *[\ \	]-Wno-sign-compare[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -Wno-sign-compare" ;;
-  esac
-  case " $CFLAGS " in
-  *[\ \	]-Wno-pointer-sign[\ \	]*) ;;
-  *) if cc_supports_flag -Wno-pointer-sign; then
-        CFLAGS="$CFLAGS -Wno-pointer-sign"
-     fi
-     ;;
-  esac
-
-  # This one is special - it's not a warning override.
-  # http://bugs.freedesktop.org/show_bug.cgi?id=10599
-  case " $CFLAGS " in
-  *[\ \	]-fno-strict-aliasing[\ \	]*) ;;
-  *) CFLAGS="$CFLAGS -fno-strict-aliasing" ;;
-  esac
-  ### End disabled warnings
-
-  if test "x$enable_ansi" = "xyes"; then
-    case " $CFLAGS " in
-    *[\ \	]-ansi[\ \	]*) ;;
-    *) CFLAGS="$CFLAGS -ansi" ;;
-    esac
-
-    case " $CFLAGS " in
-    *[\ \	]-D_POSIX_C_SOURCE*) ;;
-    *) CFLAGS="$CFLAGS -D_POSIX_C_SOURCE=199309L" ;;
-    esac
-
-    case " $CFLAGS " in
-    *[\ \	]-D_BSD_SOURCE[\ \	]*) ;;
-    *) CFLAGS="$CFLAGS -D_BSD_SOURCE" ;;
-    esac
-
-    case " $CFLAGS " in
-    *[\ \	]-pedantic[\ \	]*) ;;
-    *) CFLAGS="$CFLAGS -pedantic" ;;
-    esac
-  fi
-fi]
+dnl In principle we should put WARNING_CFLAGS in each Makefile.am like
+dnl telepathy-glib does, since CFLAGS is meant to be reserved for the user...
+dnl but prepending to CFLAGS (so the user can override it with later CFLAGS)
+dnl is the next best thing
+CFLAGS="$WARNING_CFLAGS $CFLAGS"
 
 # Disabling gc-sections makes our binaries bigger, but some toolchains
 # have known-broken support for it which discards sections that are needed.
diff --git a/m4/tp-compiler-flag.m4 b/m4/tp-compiler-flag.m4
new file mode 100644
index 00000000..06deaba0
--- /dev/null
+++ b/m4/tp-compiler-flag.m4
@@ -0,0 +1,43 @@
+dnl A version of AS_COMPILER_FLAG that supports both C and C++.
+dnl Based on:
+
+dnl as-compiler-flag.m4 0.1.0
+dnl autostars m4 macro for detection of compiler flags
+dnl David Schleef <ds@schleef.org>
+dnl $Id: as-compiler-flag.m4,v 1.1 2005/06/18 18:02:46 burgerman Exp $
+
+dnl TP_COMPILER_FLAG(CFLAGS, ACTION-IF-ACCEPTED, [ACTION-IF-NOT-ACCEPTED])
+dnl Tries to compile with the given CFLAGS and CXXFLAGS.
+dnl
+dnl Runs ACTION-IF-ACCEPTED if the compiler for the currently selected
+dnl AC_LANG can compile with the flags, and ACTION-IF-NOT-ACCEPTED otherwise.
+
+AC_DEFUN([TP_COMPILER_FLAG],
+[
+  AC_MSG_CHECKING([to see if compiler understands $1])
+
+  save_CFLAGS="$CFLAGS"
+  save_CXXFLAGS="$CXXFLAGS"
+  CFLAGS="$CFLAGS $1"
+  CXXFLAGS="$CXXFLAGS $1"
+
+  AC_TRY_COMPILE([ ], [], [flag_ok=yes], [flag_ok=no])
+  CFLAGS="$save_CFLAGS"
+  CXXFLAGS="$save_CXXFLAGS"
+
+  if test "X$flag_ok" = Xyes ; then
+    $2
+    true
+  else
+    $3
+    true
+  fi
+  AC_MSG_RESULT([$flag_ok])
+])
+
+dnl TP_ADD_COMPILER_FLAG(VARIABLE, CFLAGS)
+dnl Append CFLAGS to VARIABLE if the compiler supports them.
+AC_DEFUN([TP_ADD_COMPILER_FLAG],
+[
+  TP_COMPILER_FLAG([$2], [$1="[$]$1 $2"])
+])
diff --git a/m4/tp-compiler-warnings.m4 b/m4/tp-compiler-warnings.m4
new file mode 100644
index 00000000..ee4af310
--- /dev/null
+++ b/m4/tp-compiler-warnings.m4
@@ -0,0 +1,49 @@
+dnl TP_COMPILER_WARNINGS(VARIABLE, WERROR_BY_DEFAULT, DESIRABLE, UNDESIRABLE)
+dnl $1 (VARIABLE): the variable to put flags into
+dnl $2 (WERROR_BY_DEFAULT): a command returning true if -Werror should be the
+dnl     default
+dnl $3 (DESIRABLE): warning flags we want (e.g. all extra shadow)
+dnl $4 (UNDESIRABLE): warning flags we don't want (e.g.
+dnl   missing-field-initializers unused-parameter)
+AC_DEFUN([TP_COMPILER_WARNINGS],
+[
+  AC_REQUIRE([AC_ARG_ENABLE])dnl
+  AC_REQUIRE([AC_HELP_STRING])dnl
+  AC_REQUIRE([TP_COMPILER_FLAG])dnl
+
+  tp_warnings=""
+  for tp_flag in $3; do
+    TP_COMPILER_FLAG([-W$tp_flag], [tp_warnings="$tp_warnings -W$tp_flag"])
+  done
+
+  tp_error_flags="-Werror"
+  TP_COMPILER_FLAG([-Werror], [tp_werror=yes], [tp_werror=no])
+
+  for tp_flag in $4; do
+    TP_COMPILER_FLAG([-Wno-$tp_flag],
+      [tp_warnings="$tp_warnings -Wno-$tp_flag"])
+dnl Yes, we do need to use both -Wno-foo and -Wno-error=foo. Simon says:
+dnl     some warnings we explicitly don't want, like unused-parameter, but
+dnl     they're in -Wall. when a distro using cdbs compiles us, we have:
+dnl       -Werror -Wno-unused-parameter      -Wall
+dnl         ^ from us                         ^ from cdbs
+dnl     which turns -Wunused-parameter back on, in effect
+    TP_COMPILER_FLAG([-Wno-error=$tp_flag],
+      [tp_error_flags="$tp_error_flags -Wno-error=$tp_flag"], [tp_werror=no])
+  done
+
+  AC_ARG_ENABLE([Werror],
+    AC_HELP_STRING([--disable-Werror],
+      [compile without -Werror (normally enabled in development builds)]),
+    tp_werror=$enableval, :)
+
+  if test "x$tp_werror" = xyes && $2; then
+dnl We put -Wno-error=foo before -Wno-foo because clang interprets -Wall
+dnl -Werror -Wno-foo -Wno-error=foo as “make foo a non-fatal warning”, but does
+dnl what we want if you reverse them.
+    $1="$tp_error_flags $tp_warnings"
+  else
+    $1="$tp_warnings"
+  fi
+
+])