Import tp-compiler-flag.m4 and tp-compiler-warnings.m4 from telepathy-glib

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=19681Reviewed-by: Colin Walters <walters@verbum.org>

m4/tp-compiler-flag.m4

+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"])
+])

m4/tp-compiler-warnings.m4

+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
+
+])