Keith Marshall writes: > > From autoconf-2.59 > |and in fact it is even _more_ portable: in the first case of the first > |attempt, the computation of `top_srcdir' is not portable, since not all > |shells properly understand `"`..."..."...`"'. Worse yet, not all > |shells understand `"`...\"...\"...`"' the same way. There is just no > |portable way to use double-quoted strings inside double-quoted > |back-quoted expressions (pfew!). > > Granted, that's referring primarily to nested double quotes, with > backtick substitution,
The bug for which you posted URLs does not deal with nested double quotes nor was it reported for assignments (but see below). Of the shells I use, only pdksh (in Posix mode) has the bug that is mentioned in the quoted part of the documentation. > but there is an inference that the two interact in > a non-portable manner, which is best avoided. If we need to rely on inference in order to make good use of the documentation, then it is not as good as it should be: it should list explicitly, and detailedly the constructs that do not work, possibly also why they don't work, and best with shells and systems mentioned on which they fail, including versions, so that one can decide whether this is an ancient bug or a recent one. If we can't analyze bugs well, it may be useful to advise against a class of expressions; but then, that _still_ should be done by precisely saying what should not be used, not by inference from examples alone. The text given in the current documentation does not encompass this new bug. I have tried the MSYS shell now. I can reproduce the bug mentioned in the URLs there, but not on Cygwin, neither with bash on any other system I could find, nor with /bin/sh on FreeBSD 5.4, OpenBSD 3.8, AIX 4.3.3 HP-UX 10.20, IRIX 6.5, Solaris 2.6, Tru64 4.0D. I don't have access to older systems. With the MSYS shell, the bug also happens on the right hand side of assignments. The bug only seems to happen if the double-quoted area extends further. So, this is ok and does not add a \01 byte in the output: echo "`./test`" echo "`./test`"" -lpq" while this is not ok: echo "`./test` -lpq" If the "other shells" that have this (or a similar) bug work similarly, the second line would be a nice workaround that would not require to use intermediate variables. Luckily most instances in Autoconf and Libtool use one of the first two expressions, or use the third but are not sensitive to the extra byte in the output. So, any chance you could take a look (or give more hints) on which other systems this may go wrong, and also whether I should file a bug with bash or whether this is MSYS specific? BTW, the most similar bug I could find documented was this http://www.in-ulm.de/~mascheck/bourne/par_here_com.html which is still clearly distinct and presumably extinct or irrelevant now. Cheers, Ralf _______________________________________________ Autoconf mailing list Autoconf@gnu.org http://lists.gnu.org/mailman/listinfo/autoconf
