On 09/17/2010 10:25 AM, Sam Steingold wrote:
google appears to suggest that $ac_t is widely used in older configure
scripts as a tab character, e.g.:
echo "$ac_t""found" 1>&6
it appears that it it not mentioned in any docs and not defined to
anything useful for some time.
Commit ab7322949, 1124 commits before the long-ancient 2.50 release:
2000-02-25 Akim Demaille <akim@xxxxxxxx>
Export the knowledge on disabling echo's trailing new line.
* acspecific.m4 (AC_PROG_ECHO_N): Rename as...
(_AC_PROG_ECHO): this.
Set ECHO_N, ECHO_C, ECHO_T instead of ac_n, ac_c and ac_t.
At that point, $ac_t was no longer defined by autoconf, so anyone using
it now gets "" instead of "<tab>".
Really, anyone with $ac_t in their script should modernize, and use
ECHO_T instead.
since recently, however, it is used in a loop setting ac_install_sh, and
now it is set to "install-sh". thus now I see configure messages like
checking for getrlimit declaration... (cached) install-shextern int
getrlimit (enum __rlimit_resource, struct rlimit *);
Thanks for the report. That's an unfortunate side effect of trying to
use a temporary variable to work around a shell portability issue with
"`""`", introduced in commit c0b647a8c, Oct 2007, 2.62 release.
Thus my questions are:
1. optional: what is the history of the matter?
I think I've covered that :)
2. required: is there a replacement for ac_t or should it be dropped?
Yes, we can avoid using $ac_t for our temporary variable name, to
respect the fact that there are some _really_ old scripts that are
exploiting formerly undocumented internals that no longer exist.
Although those configure.in should be modernized, we can at least make
their output look prettier with a simple change to avoid the problematic
name.
--
Eric Blake eblake@xxxxxxxxxx +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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