1 files changed, 49 insertions, 0 deletions
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
+
+])