Re: LIBS

[Bastien ROUCARIES]

On Sat, Jul 20, 2013 at 5:34 AM, Russ Allbery <address@hidden> wrote:
> Harlan Stenn <address@hidden> writes:
>
>> So for reasons that may or may not still be valid, I've had folks
>> successfully lobby me to separate out libraries that are needed for all
>> programs from libraries that are needed for certain programs.
>
>> I believe the reasons for this have to do with the size of the
>> executables - folks Noticed that linking with unnecessary libraries
>> caused the resulting executables to be much bigger and sucked up memory,
>> especially in embedded systems.
>
>> But if I don't put all of the detected libraries in LIBS then things
>> like AC_CHECK_FUNCS won't find them.
>
>> Suggestions on good ways to proceed?
>
> I do lots and lots and lots of this sort of thing:

Russ could you add some proper licence text to this ? Preferally all
permissive license ?

I will add your stuff to autoconf-archive as an optionnal flags to:
AX_SAVE_FLAGS/AX_RESTORE_FLAGS
(see 
http://www.gnu.org/software/autoconf-archive/ax_save_flags.html#ax_save_flags)
and I will add the AX_SWITCH_FLAGS macro
> dnl Add the library flags to the default compiler flags and then remove them.
> dnl
> dnl To use these macros, pass the prefix string used for the variables as the
> dnl only argument.  For example, to use these for a library with KRB5 as a
> dnl prefix, one would use:
> dnl
> dnl     AC_DEFUN([RRA_LIB_KRB5_SWITCH], [RRA_LIB_HELPER_SWITCH([KRB5])])
> dnl     AC_DEFUN([RRA_LIB_KRB5_RESTORE], [RRA_LIB_HELPER_RESTORE([KRB5])])
> dnl
> dnl Then, wrap checks for library features with RRA_LIB_KRB5_SWITCH and
> dnl RRA_LIB_KRB5_RESTORE.
> AC_DEFUN([RRA_LIB_HELPER_SWITCH],
> [rra_$1[]_save_CPPFLAGS="$CPPFLAGS"
>  rra_$1[]_save_LDFLAGS="$LDFLAGS"
>  rra_$1[]_save_LIBS="$LIBS"
>  CPPFLAGS="$$1[]_CPPFLAGS $CPPFLAGS"
>  LDFLAGS="$$1[]_LDFLAGS $LDFLAGS"
>  LIBS="$$1[]_LIBS $LIBS"])
>
> AC_DEFUN([RRA_LIB_HELPER_RESTORE],
> [CPPFLAGS="$rra_$1[]_save_CPPFLAGS"
>  LDFLAGS="$rra_$1[]_save_LDFLAGS"
>  LIBS="$rra_$1[]_save_LIBS"])
>
> combined with adding libraries explicitly to XXX_LIBS in the probe macros,
> and then linking with XXX_LDFLAGS and XXX_LIBS when that library is
> needed.  It gets quite tedious, but it does work, including on hosts where
> --as-needed isn't supported.
>
> --
> Russ Allbery (address@hidden)             <http://www.eyrie.org/~eagle/>
>
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