configure: new option --enable-gcc-warnings

[bpt/emacs.git] / m4 / warnings.m4

# warnings.m4 serial 6
dnl Copyright (C) 2008-2012 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

dnl From Simon Josefsson

# gl_AS_VAR_APPEND(VAR, VALUE)
# ----------------------------
# Provide the functionality of AS_VAR_APPEND if Autoconf does not have it.
m4_ifdef([AS_VAR_APPEND],
[m4_copy([AS_VAR_APPEND], [gl_AS_VAR_APPEND])],
[m4_define([gl_AS_VAR_APPEND],
[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])


# gl_WARN_ADD(PARAMETER, [VARIABLE = WARN_CFLAGS])
# ------------------------------------------------
# Adds parameter to WARN_CFLAGS if the compiler supports it.  For example,
# gl_WARN_ADD([-Wparentheses]).
#
# If VARIABLE is a variable name, AC_SUBST it.
AC_DEFUN([gl_WARN_ADD],
dnl FIXME: gl_Warn must be used unquoted until we can assume
dnl autoconf 2.64 or newer.
[AS_VAR_PUSHDEF([gl_Warn], [gl_cv_warn_[]_AC_LANG_ABBREV[]_$1])dnl
AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [
  gl_save_compiler_FLAGS="$gl_Flags"
  gl_Flags="$gl_Flags $1"
  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
                    [AS_VAR_SET(gl_Warn, [yes])],
                    [AS_VAR_SET(gl_Warn, [no])])
  gl_Flags="$gl_save_compiler_FLAGS"
])
AS_VAR_IF(gl_Warn, [yes],
  [gl_AS_VAR_APPEND(m4_if([$2], [], [[WARN_CFLAGS]], [[$2]]), [" $1"])])
AS_VAR_POPDEF([gl_Flags])dnl
AS_VAR_POPDEF([gl_Warn])dnl
m4_ifval([$2], [AS_LITERAL_IF([$2], [AC_SUBST([$2])], [])])dnl
])