On Fri, 14 Dec 2018 at 14:51, Nick Bowler <nbow...@draconx.ca> wrote:
> > If you want to set a value to a variable only if the variable is > unset, a typical way to do that in shell programming is: > > : "${FOO=value-if-unset}" > > Or if you prefer also to set it the variable is _empty_ (i.e., including > the case where it is set to the empty string): > > : "${FOO:=value-if-empty}"-- > So the answer seems to be "do it with shell". I still get confused (as here) with whether it's possible (or good style) to use shell directly, or whether there's something I should be doing with autoconf macros. So in the end I have this: dnl Set size of word and address AC_ARG_VAR([WORD_SIZE], [value of WORD_SIZE register [default: sizeof(long)]]) AC_CHECK_SIZEOF([long]) : "${WORD_SIZE=SIZEOF_LONG}" AC_ARG_VAR([ADDRESS_SIZE], [value of ADDRESS_SIZE register [default: sizeof(size_t)]]) AC_CHECK_SIZEOF([size_t]) : "${ADDRESS_SIZE=SIZEOF_SIZE_T}" Does that look about right? -- https://rrt.sc3d.org