Re: [Qemu-devel] [PATCH v2] Remove the extra -lrt switch

[Eric Blake]

On 04/27/2012 04:20 PM, Andreas Färber wrote:
> Am 27.04.2012 23:55, schrieb Eric Blake:
>> On 04/27/2012 02:16 PM, Peter Portante wrote:
>>> The package config check for gthreads might have already placed a
>>> -lrt switch in LIBS earlier.
>>>
>>> Refactored the code from the pthread switch removal, from commit 
>>> e3c56761b465a4253871c32b06ebbc2d8b3fc3e1, to make it work for
>>> the more general case.
>>>
> 
>>> +add_to_libs() { +  found=no +  for lib_entry in $LIBS; do +
>>> if test "$lib_entry" = "$1"; then +      found=yes +      break +
>>> fi +  done +  if test "$found" = "no"; then +    LIBS="$1 $LIBS" 
>>> +  fi +}
> 
>> Shorter (and probably faster) to write this as:
> 
>> add_to_libs() { case " $LIBS " in " $1 ") ;; *) LIBS="$1 $LIBS" ;; 
>> esac }
> 
> Er, no. That would only catch the initial duplication case -lrt -lrt
> but not -lbla -lrt -lrt or -lrt -lbla -lrt, wouldn't it?
> 
> But then again Peter's function wouldn't find duplicates when $1
> contains a space either... tricky.

If you want to filter duplicates out of $1, then:

add_to_libs() {
  for lib in $1; do
    case " $LIBS " in
      *" $lib "*) ;;
      *) LIBS="$lib $LIBS" ;;
    esac
  done
}

Hopefully, we don't encounter any libs with circular dependencies, where
a lib must be listed twice to be effective.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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