On 09/25/2010 12:22 PM, Ben Pfaff wrote:
retitle 593838 AX_CFLAGS_GCC_OPTION misuses AS_VAR_PUSHDEF variable
reassign 593838 autoconf-archive
thanks
Jerome BENOIT<jgm...@rezozer.net> initially reported that
AX_CFLAGS_GCC_OPTION(-std=c99) fails with Autoconf 2.67. Vincent
Bernat<ber...@debian.org> determined that the bug could be fixed
by replacing a literal shell assignment by AS_VAR_SET.
Just now, I took a closer look. I was able to reduce the problem
to the following trivial case:
--8<--------------------------cut here-------------------------->8--
AC_DEFUN([MY_MACRO],
[AS_VAR_PUSHDEF([VAR],[prefix_$1])
dnl This is the version used by AX_CFLAGS_GCC_OPTION.
dnl I believe that it is incorrect. It does not work on Autoconf>= 2.67.
VAR=the_value
You are correct that this will not work if VAR is an indirect variable
name. It all depends on whether $1 is determined to be an indirection.
MY_MACRO([blah])
is direct; it expands to AS_VAR_PUSHDEF([VAR],[prefix_blah]), at which
point VAR is the literal string prefix_blah, and you still have valid
shell code (by sheer luck, and not because you followed the
documentation). But
foo=bar
MY_MACRO([$foo])
is indirect; it expands to AS_VAR_PUSHDEF([VAR],[prefix_$foo]), and you
MUST use AS_VAR_SET([VAR]) in order to set the shell variable prefix_bar
(as that is what the indirection results in). Direct use of VAR as a
shell-variable name will result in invalid shell code.
On that basis, I infer that one is not supposed to use the
M4-NAME literally, and thus I believe that this is a bug in
AX_CFLAGS_GCC_OPTION. So, I am reassigning this bug to
autoconf-archive (with this email).
That is the correct course of action.
--
Eric Blake ebl...@redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
