Hello Ralf,
the two aspects are:
1) If the information about signedness of char is needed at
build-time, it's better to use limits.h. Such projects should not
use AC_C_CHAR_UNSIGNED. That is why the manual should generally
recommend not to use the macro.
2) If signedness of char has to be known during configure time
AC_C_CHAR_UNSIGNED is still useful.
About the patch I posted:
I would like to advertise 1). Thusly, I'd prefer if "autoconf -Wall"
printed out the message that AC_C_CHAR_UNSIGNED is probably no longer
needed.
If someone needs to know the signedness at configure time, they can
perform a check based on limits.h or copy the body of
AC_C_CHAR_UNSIGNED. I believe this need is relatively rare, so the
slight discomfort is well overweighted by the fact that the warning
message help to squash the unnecesary AC_C_CHAR_UNSIGNED in many
project.
Ralf, does the above convert you to approve my patch?
I'd also like to hear others' opinions.
Have a nice day,
Stepan