source: kBuild/trunk/src/grep/m4/warnings.m4

# warnings.m4 serial 16
dnl Copyright (C) 2008-2021 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_COMPILER_OPTION_IF(OPTION, [IF-SUPPORTED], [IF-NOT-SUPPORTED],
#                       [PROGRAM = AC_LANG_PROGRAM()])
# -----------------------------------------------------------------
# Check if the compiler supports OPTION when compiling PROGRAM.
#
# The effects of this macro depend on the current language (_AC_LANG).
AC_DEFUN([gl_COMPILER_OPTION_IF],
[
AS_VAR_PUSHDEF([gl_Warn], [gl_cv_warn_[]_AC_LANG_ABBREV[]_$1])dnl
AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
AS_LITERAL_IF([$1],
  [m4_pushdef([gl_Positive], m4_bpatsubst([$1], [^-Wno-], [-W]))],
  [gl_positive="$1"
case $gl_positive in
  -Wno-*) gl_positive=-W`expr "X$gl_positive" : 'X-Wno-\(.*\)'` ;;
esac
m4_pushdef([gl_Positive], [$gl_positive])])dnl
AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], [gl_Warn], [
  gl_save_compiler_FLAGS="$gl_Flags"
  gl_AS_VAR_APPEND(m4_defn([gl_Flags]),
    [" $gl_unknown_warnings_are_errors ]m4_defn([gl_Positive])["])
  AC_LINK_IFELSE([m4_default([$4], [AC_LANG_PROGRAM([[]])])],
                 [AS_VAR_SET([gl_Warn], [yes])],
                 [AS_VAR_SET([gl_Warn], [no])])
  gl_Flags="$gl_save_compiler_FLAGS"
])
AS_VAR_IF(gl_Warn, [yes], [$2], [$3])
m4_popdef([gl_Positive])dnl
AS_VAR_POPDEF([gl_Flags])dnl
AS_VAR_POPDEF([gl_Warn])dnl
])

# gl_UNKNOWN_WARNINGS_ARE_ERRORS
# ------------------------------
# Clang doesn't complain about unknown warning options unless one also
# specifies -Wunknown-warning-option -Werror.  Detect this.
#
# The effects of this macro depend on the current language (_AC_LANG).
AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS],
[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])

# Specialization for _AC_LANG = C. This macro can be AC_REQUIREd.
AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS(C)],
[
  AC_LANG_PUSH([C])
  gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL
  AC_LANG_POP([C])
])

# Specialization for _AC_LANG = C++. This macro can be AC_REQUIREd.
AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS(C++)],
[
  AC_LANG_PUSH([C++])
  gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL
  AC_LANG_POP([C++])
])

# Specialization for _AC_LANG = Objective C. This macro can be AC_REQUIREd.
AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS(Objective C)],
[
  AC_LANG_PUSH([Objective C])
  gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL
  AC_LANG_POP([Objective C])
])

AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL],
[gl_COMPILER_OPTION_IF([-Werror -Wunknown-warning-option],
   [gl_unknown_warnings_are_errors='-Wunknown-warning-option -Werror'],
   [gl_unknown_warnings_are_errors=])])

# gl_WARN_ADD(OPTION, [VARIABLE = WARN_CFLAGS/WARN_CXXFLAGS],
#             [PROGRAM = AC_LANG_PROGRAM()])
# -----------------------------------------------------------
# Adds parameter to WARN_CFLAGS/WARN_CXXFLAGS if the compiler supports it
# when compiling PROGRAM.  For example, gl_WARN_ADD([-Wparentheses]).
#
# If VARIABLE is a variable name, AC_SUBST it.
#
# The effects of this macro depend on the current language (_AC_LANG).
AC_DEFUN([gl_WARN_ADD],
[AC_REQUIRE([gl_UNKNOWN_WARNINGS_ARE_ERRORS(]_AC_LANG[)])
gl_COMPILER_OPTION_IF([$1],
  [gl_AS_VAR_APPEND(m4_if([$2], [], [[WARN_]_AC_LANG_PREFIX[FLAGS]], [[$2]]), [" $1"])],
  [],
  [$3])
m4_ifval([$2],
         [AS_LITERAL_IF([$2], [AC_SUBST([$2])])],
         [AC_SUBST([WARN_]_AC_LANG_PREFIX[FLAGS])])dnl
])

# Local Variables:
# mode: autoconf
# End: