build-sys: exclude some CC warnings for clang

[thirdparty/util-linux.git] / m4 / compiler.m4

dnl Copyright (C) 2008-2011 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
dnl -- derivated from coreutils m4/warnings.m4

# UL_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], [UL_AS_VAR_APPEND])],
[m4_define([UL_AS_VAR_APPEND],
[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])

#
# Adds parameter to WARN_CFLAGS if the compiler supports it.
#
AC_DEFUN([UL_ADD_WARN_CFLAG], [
  AS_VAR_PUSHDEF([ul_Warn], [ul_cv_warn_$1])dnl
  AC_CACHE_CHECK([whether compiler handles $1], m4_defn([ul_Warn]), [
    ul_save_CPPFLAGS="$CPPFLAGS"
    CPPFLAGS="${CPPFLAGS} $1"
    AC_PREPROC_IFELSE([AC_LANG_PROGRAM([])],
                      [AS_VAR_SET(ul_Warn, [yes])],
                      [AS_VAR_SET(ul_Warn, [no])])
    CPPFLAGS="$ul_save_CPPFLAGS"
  ])
  AS_VAR_IF(ul_Warn, [yes], [UL_AS_VAR_APPEND([WARN_CFLAGS], [" $1"])])
])

# UL_WARN_ADD(PARAMETER, [EXCLUDE_CC_LIST])
# -----------------------------------------
# Adds parameter to WARN_CFLAGS if the compiler supports it. Ignore the
# parameter if compiler is in exclude list.
AC_DEFUN([UL_WARN_ADD], [
m4_ifval([$2], [
  warn_exclude="$2"
  case $compiler_clang in
    yes) warn_cc=clang ;;
      *) warn_cc=$CC ;;
  esac
  case ${warn_exclude} in
    *${warn_cc}*)
      AC_MSG_CHECKING([whether compiler handles $1])
      AC_MSG_RESULT([excluded])
      ;;
    *)
      UL_ADD_WARN_CFLAG([$1])
      ;;
  esac],
  [UL_ADD_WARN_CFLAG([$1])])
])


# UL_PROG_CLANG
# -------------
# Checks if compiler is clang, defines compiler_clang=yes if yes.
#
# Note that generic CC variable is not modified by this function.  It's
# possible that CC is set to 'cc' and the file /usr/bin/cc is a symlink to
# /usr/bin/clang, then compiler_clang is also set ot 'yes'.
AC_DEFUN([UL_PROG_CLANG], [
  AC_REQUIRE([AC_PROG_CC])
  AC_CACHE_CHECK([whether clang is in use], [ul_cv_clang], [
    case ${CC} in #(
      *gcc*)   ul_cv_clang=no ;;
      *clang*) ul_cv_clang=yes ;;
      *) AC_COMPILE_IFELSE([AC_LANG_SOURCE([int main() {
           #ifdef __clang__
               return 0;
             #else
               #error The __clang__ was not defined
             #endif
           }])],
           [ul_cv_clang=yes],
           [ul_cv_clang=no]
         ) ;;
    esac
  ])
  compiler_clang=$ul_cv_clang
])