On 27/07/2017 16:24, Eric Blake wrote:
On 07/27/2017 08:13 AM, Bosco wrote:
On 27 July 2017 at 12:54, Eric Blake <eblake@xxxxxxxxxx> wrote:
Which man pages? Echo is one of those programs that varies widely, and
you are MUCH better off using printf(1) instead of echo(1) if you are
trying to get newline suppression, trying to print something that might
begin with -, or trying to print something that might contain \.
Sorry, maybe I did't explain it correctly, I mean the man pages of the
dash source:
https://git.kernel.org/pub/scm/utils/dash/dash.git/tree/src/dash.1#n1202
And because of this, I got an error compiling zziplib, you may see
https://github.com/gdraheim/zziplib/blob/v0.13.67/configure#L17542
Eww - storing generated files in git - that forces everyone that checks
out your project to use the EXACT same version of autotools to avoid
changing the generated files unintentionally.
Looking at those lines:
if test -f $ac_prefix_conf_INP ; then
echo "s/^#undef *\\([ABCDEFGHIJKLMNOPQRSTUVWXYZ_]\\)/#undef $ac_prefix_conf_UPP""_\\1/" > conftest.prefix
ac_prefix_conf_INP is not defined anywhere in autoconf 2.69 sources (and
you really shouldn't use the ac_ prefix if you are writing code that is
not part of autoconf proper). I couldn't find mention of it at
https://github.com/gdraheim/zziplib/blob/v0.13.67/configure.ac, but it
may be in one of your other included files. Can you pinpoint which part
of your configure.ac results in that part of the generated configure
file? In all likelihood, you are using a buggy macro that is using
autoconf primitives incorrectly, and thus resulting in non-portable
code. But without seeing the true source, I can't help you debug your
problem.
This is coming from zziplib's outdated copy of ax_prefix_config_h.m4,
for which I submitted a patch to make it work in dash, and which was
accepted, back in 2010 (!): <https://savannah.gnu.org/patch/?7317>
zziplib should update to a current version of this file.
Arguably, since it is not required by POSIX, we don't have to do it. But
I also can't argue that POSIX forbids us to support \1 as an extension
(it says nothing about whether implementations can have additional
escape sequences). So I'll argue that it is intentional as a dash
extension. But if you can make dash smaller by getting rid of the
extension, that might be an acceptable patch.
In that case, I think, the man page of dash should be modified with
that extension.
Indeed, or the fact that it is NOT documented means that it is an
unintentional bug for providing the extension.
The man page of dash states:
All other backslash sequences elicit undefined behaviour.
Implementation-wise, POSIX gives the same requirements for escape
sequences for echo as for printf %b, therefore it makes sense to share
the code between the two. Neither echo nor printf %b requires \1 to be
treated as an escape sequence, but both allow it.
bash treats \1 as an escape sequence with printf %b. For compatibility
with bash, it sort of makes sense to implement this in dash as well. Yet
for some reason, bash *doesn't* treat \1 as an escape sequence with
echo, not even with echo -e.
Keeping dash small, continuing to share the code between the two cases,
can only mean behaving differently from bash in at least one of them.
Cheers,
Harald van Dijk
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