CF_CLANG_COMPILER

dnl CF_CLANG_COMPILER version: 8 updated: 2021/01/01 13:31:04
dnl -----------------
dnl Check if the given compiler is really clang.  clang's C driver defines
dnl __GNUC__ (fooling the configure script into setting $GCC to yes) but does
dnl not ignore some gcc options.
dnl
dnl This macro should be run "soon" after AC_PROG_CC or AC_PROG_CPLUSPLUS, to
dnl ensure that it is not mistaken for gcc/g++.  It is normally invoked from
dnl the wrappers for gcc and g++ warnings.
dnl
dnl $1 = GCC (default) or GXX
dnl $2 = CLANG_COMPILER (default)
dnl $3 = CFLAGS (default) or CXXFLAGS
AC_DEFUN([CF_CLANG_COMPILER],[
ifelse([$2],,CLANG_COMPILER,[$2])=no

if test "$ifelse([$1],,[$1],GCC)" = yes ; then
	AC_MSG_CHECKING(if this is really Clang ifelse([$1],GXX,C++,C) compiler)
	cf_save_CFLAGS="$ifelse([$3],,CFLAGS,[$3])"
	AC_TRY_COMPILE([],[
#ifdef __clang__
#else
make an error
#endif
],[ifelse([$2],,CLANG_COMPILER,[$2])=yes
],[])
	ifelse([$3],,CFLAGS,[$3])="$cf_save_CFLAGS"
	AC_MSG_RESULT($ifelse([$2],,CLANG_COMPILER,[$2]))
fi

CLANG_VERSION=none

if test "x$ifelse([$2],,CLANG_COMPILER,[$2])" = "xyes" ; then
	case "$CC" in
	(c[[1-9]][[0-9]]|*/c[[1-9]][[0-9]])
		AC_MSG_WARN(replacing broken compiler alias $CC)
		CFLAGS="$CFLAGS -std=`echo "$CC" | sed -e 's%.*/%%'`"
		CC=clang
		;;
	esac

	AC_MSG_CHECKING(version of $CC)
	CLANG_VERSION="`$CC --version 2>/dev/null | sed -e '2,$d' -e 's/^.*(CLANG[[^)]]*) //' -e 's/^.*(Debian[[^)]]*) //' -e 's/^[[^0-9.]]*//' -e 's/[[^0-9.]].*//'`"
	test -z "$CLANG_VERSION" && CLANG_VERSION=unknown
	AC_MSG_RESULT($CLANG_VERSION)

	for cf_clang_opt in \
		-Qunused-arguments \
		-Wno-error=implicit-function-declaration
	do
		AC_MSG_CHECKING(if option $cf_clang_opt works)
		cf_save_CFLAGS="$CFLAGS"
		CFLAGS="$CFLAGS $cf_clang_opt"
		AC_TRY_LINK([
			#include <stdio.h>],[
			printf("hello!\\n");],[
			cf_clang_optok=yes],[
			cf_clang_optok=no])
		AC_MSG_RESULT($cf_clang_optok)
		CFLAGS="$cf_save_CFLAGS"
		if test "$cf_clang_optok" = yes; then
			CF_VERBOSE(adding option $cf_clang_opt)
			CF_APPEND_TEXT(CFLAGS,$cf_clang_opt)
		fi
	done
fi
])