[Libcdio-devel] problems with sed test

[Robert William Fuller]

Consider the following code in configure.ac:

SED_EXTENDED_RE_FLAG='-r'
result=$(echo 'define' | $ac_path_SED -r -e 's/^define/foo/' 2>/dev/null)
if [[ $? -ne 0 ]] ; then
   result=$(echo 'define' | $ac_path_SED -r -E 's/^define/foo/' 
2>/dev/null)
   if [[ $? -ne 0 ]] ; then
     SED_EXTENDED_RE_FLAG='-E'
   else
     AC_MSG_WARN([Don't have SED that understand extended RE's. Some 
minor compilation issues may fail.])
     SED_EXTENDED_RE_FLAG=''
   fi
fi

Now consider that the second test ought to be [[ $? -eq 0 ]] because 
we're checking to see if the -E flag works.  BUT, the second invocation 
of sed will never succeed because the -r and the -E flag are mutually 
exclusive.  One exists on one platform and not the other.  So the second 
run of sed really ought to be "-E -e" not "-r -E".  (I suspect that 
someone accidentally changed the wrong option during a copy and paste of 
the prior invocation when they wrote this code originally.)

Supposing we make all these changes, this still won't work on MacOS 
because it has ac_path_SED set to /usr/X11/bin/gsed which does not 
exist.  We should use the SED variable rather than ac_path_SED.  So when 
all is sed and done, it should look like this:

SED_EXTENDED_RE_FLAG='-r'
result=$(echo 'define' | $SED -r -e 's/^define/foo/' 2>/dev/null)
if [[ $? -ne 0 ]] ; then
    result=$(echo 'define' | $SED -E -e 's/^define/foo/' 2>/dev/null)
    if [[ $? -eq 0 ]] ; then
        SED_EXTENDED_RE_FLAG='-E'
    else
        AC_MSG_WARN([Don't have SED that understand extended RE's. Some 
minor compilation issues may fail.])
        SED_EXTENDED_RE_FLAG=''
    fi
fi

Thoughts?

Rob