Re: AC_CHECK_LIB: Library is found on build host but is not on a target host

[Eric Blake]

> > [I reiterate - I do NOT want these mails coming only to me, when I have
> > asked for them to go to the list]
>
> Sorry it was not my will send mails to you only :(  Either is a fault
> on gmail or (perhaps?) the mailing list... I *always* have clicked on
> Reply button... in fact recent now I realize of that, I haven't this
> problem on other lists....

In general, on technical lists you should use the 'Reply-All' button, 
not the 'Reply' button.  Most likely, the other lists you refer to used 
reply-to-munging, but that is considered harmful on this list.

> > Ah - the difference is the presence of -L/usr/lib/mysql in the working
> > command line.  For your configure test to work, you'd also have to provide
> > that same -L option to LDFLAGS prior to using AC_CHECK_LIB (or the better
> > AC_SEARCH_LIBS).
>
> But I don't understand why... with AC_CHECK_LIB I have no need to use
> LDFLAGS on Mandriva or Ubuntu...

Most likely, because Mandriva or Ubuntu chooses to install the package 
directly into /usr/lib instead of Fedora's choice of installing into 
/usr/lib/mysql (I don't use Ubuntu myself to state that with certainty). 
 I can't say whether the difference in layout between the distros is 
worthy of a bug report (or even to which distro you should file such a 
bug report), but that's one of the joys you get to encounter when 
porting software to multiple platforms.  More importantly, you should 
remember that someone might not have mysql installed anywhere under 
/usr/lib at all; perhaps they installed it in $HOME/lib instead.

Hence, the autoconf approach is to expose LDFLAGS as the desired way of 
letting the user tune where to look for particular libraries, and both 
the autoconf-archives and gnulib projects have written wrapper macros 
that make it easier to search in several default candidate locations 
(including the location relative to ${prefix}) to set the correct 
LDFLAGS for a given library.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org