On 08 Dec 2021 15:03, Jon Turney wrote:
> +AC_ARG_ENABLE(doc,
> +	      [AS_HELP_STRING([--enable-doc], [Build documentation])],
> +	      enable_doc=$enableval,
> +	      enable_doc=yes)

the 3rd arg is redundant.  you can just write ,, to use the default iirc.

> +AC_CHECK_PROGS([DOCBOOK2XTEXI], [docbook2x-texi db2x_docbook2texi])
> +AC_CHECK_PROGS([XMLTO], [xmlto])
> +
> +if test "x$enable_doc" != "xno"; then
> +   if test -z "$DOCBOOK2XTEXI" || test -z "$XMLTO"; then
> +       AC_MSG_ERROR([Required documentation tools not found])
> +   fi
> +fi

i think AM_MISSING_PROG would be more appropriate.  then you don't need
the `test` logic.
https://www.gnu.org/software/automake/manual/html_node/Public-Macros.html#index-AM_005fMISSING_005fPROG
-mike