`printf -v` is not available in some shells

[sparr]

There are four instances of printf -v in funclib.sh (e.g. https://github.com/gnulib-modules/bootstrap/blob/master/build-aux/funclib.sh#L1156) which do not work in the dash shell. Although that file doesn't specify #!/bin/sh, the bootstrap script it ends up included in does. These printf -v var ... should be replaced with var="$(printf ...)" which will allow the tests in question to proceed on dash and potentially get a faster func_quotefast_eval than the fallback.

See: https://salsa.debian.org/debian/devscripts/-/blob/main/scripts/checkbashisms.pl?ref_type=heads#L706 (against which I'll be submitting a patch about the quoting shortly)

[gvvaughan]

Thanks for the report, but I'm not inclined to change anything in this case:

if test xyes = `(x=; printf -v x %q yes; echo x"$x") 2>/dev/null`; then
  printf -v _GL_test_printf_tilde %q '~'
  if test '\~' = "$_GL_test_printf_tilde"; then
    func_quotefast_eval ()
    {
      printf -v func_quotefast_eval_result %q "$1"
    }
  else
    # Broken older Bash implementations.  Make those faster too if possible.
    func_quotefast_eval ()
    {
      case $1 in
        '~'*)
          func_quote_portable false "$1"
          func_quotefast_eval_result=$func_quote_portable_result
          ;;
        *)
          printf -v func_quotefast_eval_result %q "$1"
          ;;
      esac
    }
  fi
else
  func_quotefast_eval ()
  {
    func_quote_portable false "$1"
    func_quotefast_eval_result=$func_quote_portable_result
  }
fi

You'll note that we only actually call printf -v after it has been test to be callable successfully, so it's never executed where it's not supported. It would be easy to fix up all but the first instance for tidiness, but I don't see a clean portable way to rewrite the first instance of

test xyes = `(x=; printf -v x %q yes; echo x"$x") 2>/dev/null`

...and since this code is executed in all kinds of unusual and ancient shells by libtool and m4, it's not worth the risk of trying to futz with it IMHO.