Stepan Kasal <[EMAIL PROTECTED]> writes:
> * lib/m4sugar/m4sh.m4 (_AS_HERE_DOC_WORKS): Check for the
> ksh93f bug with long here-documents.
> (AS_INIT): Require this check.
I have some qualms about this, on efficiency grounds. It will slow
down startup, for the sake only of (as far as we know) Unixware 7.1.1
which is a minority system. Isn't there a faster way to do this?
The documentation change looks good, though. Thanks. I tweaked it a
bit and installed this:
2006-06-02 Stepan Kasal <[EMAIL PROTECTED]>
and Paul Eggert <[EMAIL PROTECTED]>
* doc/autoconf.texi (Here-Documents): Add details about the
pre-ksh93g bug. Reword slightly to make it clearer. Consistently
use "here-documents" instead of "here documents".
--- doc/autoconf.texi 1 Jun 2006 07:47:40 -0000 1.1033
+++ doc/autoconf.texi 2 Jun 2006 22:42:10 -0000
@@ -10755,8 +10755,8 @@ Posix standard, the challenge is to find
@node Here-Documents
@section Here-Documents
[EMAIL PROTECTED] Here documents
[EMAIL PROTECTED] Shell here documents
[EMAIL PROTECTED] Here-documents
[EMAIL PROTECTED] Shell here-documents
Don't rely on @samp{\} being preserved just because it has no special
meaning together with the next symbol. In the native @command{sh}
@@ -10787,21 +10787,23 @@ bash-2.04$ @kbd{cat <<EOF
@end group
@end example
-
-Many older shells (including the Bourne shell) implement here-documents
-inefficiently. And some shells mishandle large here-documents: for example,
+Some shells mishandle large here-documents: for example,
Solaris 10 @command{dtksh} and the UnixWare 7.1.1 Posix shell, which are
derived from Korn shell version M-12/28/93d, mishandle braced variable
-expansion @[EMAIL PROTECTED]@}} that crosses a 1024- or 4096-byte buffer
boundary
-within a here-document. If the closing brace does not lie on the boundary,
-the failure is silent and the variable expansion will be empty, otherwise
-the shell will report a bad substitution. This bug can usually be worked
-around by omitting the braces: @code{$var}. The bug was fixed in
+expansion that crosses a 1024- or 4096-byte buffer boundary
+within a here-document. Only the part of the variable name after the boundary
+is used. For example, @[EMAIL PROTECTED]@}} could be replaced by the expansion
+of @[EMAIL PROTECTED]@}}. If the end of the variable name is aligned with the
block
+boundary, the shell reports an error, as if you used @[EMAIL PROTECTED]@}}.
+Instead of @[EMAIL PROTECTED]@}}, the shell may expand
[EMAIL PROTECTED]@[EMAIL PROTECTED], or even @[EMAIL PROTECTED]@}}. This bug
can often
+be worked around by omitting the braces: @code{$variable}. The bug was fixed
in
@samp{ksh93g} (1998-04-30) but as of 2006 many operating systems were
still shipping older versions with the bug.
-Some shells can be extremely inefficient when there are a lot of
-here-documents inside a single statement. For instance if your
+Many older shells (including the Bourne shell) implement here-documents
+inefficiently. In particular, some shells can be extremely inefficient when
+a single statement contains many here-documents. For instance if your
@file{configure.ac} includes something like:
@example
@@ -10820,7 +10822,7 @@ fi
@end example
A shell parses the whole @code{if}/@code{fi} construct, creating
-temporary files for each here document in it. Some shells create links
+temporary files for each here-document in it. Some shells create links
for such here-documents on every @code{fork}, so that the clean-up code
they had installed correctly removes them. It is creating the links
that can take the shell forever.
