1dnl AX_CXXFLAGS_OPTIONS(var-name, option) 2dnl add option to var-name if $CXX support it. 3AC_DEFUN([AX_CHECK_PRECOMPILED_HEADER], [ 4AC_MSG_CHECKING([whether ${CXX} support precompiled header]) 5AC_LANG_SAVE 6AC_LANG_CPLUSPLUS 7SAVE_CXXFLAGS=$CXXFLAGS 8dnl we consider than if -Winvalid-pch is accepted pch will works ... 9CXXFLAGS=-Winvalid-pch 10dnl but we don't want -Winvalid-pch else compilation will fail due -Werror and 11dnl the fact than some pch will be invalid for the given compilation option 12AC_TRY_COMPILE(,[;],AC_MSG_RESULT([yes]); $1="${$1} -include bits/stdc++.h", AC_MSG_RESULT([no])) 13CXXFLAGS=$SAVE_CXXFLAGS 14AC_LANG_RESTORE 15]) 16