On Wed, Mar 18, 2020 at 12:13 PM Nick Bowler <nbowler@xxxxxxxxxx> wrote: > On 18/03/2020, Nick Bowler <nbowler@xxxxxxxxxx> wrote: > > On 2020-03-18, Ross Burton <ross.burton@xxxxxxxxx> wrote: > > [...] > >> The flex issue is worked around by picking this commit from flex git: > >> > >> https://github.com/westes/flex/commit/c42de062bbdc7c31d7181c10a74202d493280ada > >> > >> That refers to a mail sent to bug-autoconf in February 2018, with no > >> reply: > >> > >> https://lists.gnu.org/archive/html/bug-autoconf/2018-02/msg00005.html > > [this mail describes observed problems when passing a literal 'dnl' to the > > first argument of AC_CHECK_FUNCS] > >> > >> Any thoughts? > > > > I think the linked mail stems from a misunderstanding of how m4 and > > "dnl" work. > > > > "dnl" is not really a comment like you may find in other programming > > languages. It is a macro, but one with very special semantics in that it > > influences how m4 parses the remaining input whenever it is expanded. > > > > The first argument to AC_CHECK_FUNCS is not subject to further expansion > > within the expansion of AC_CHECK_FUNCS (very typical for macros which > > take "string" arguments" in M4), so by quoting the dnl this means it is > > never expanded and thus has no effect on the M4 processing. So you have > > a string containing these characters. > > Ah, I see now: while the first argument to AC_CHECK_FUNCS is treated as > a "string" when splitting on whitespace to generate the list of function > names for Autoheader, it is not treated the same when creating the for loop. > > This is probably a mistake and the first argument should not be subject > to further expansion in any case. > > In master it seems this was further changed to use an unrolled loop in > some simple cases which may result in some altered behaviour compared to > autoconf 2.69. I think this counts as a regression and we do need to fix it so existing configure scripts continue to work. See the third of the three patches I just posted. I was able to confirm that this was indeed the problem with both flex and nasm. zw
