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@unnumbered Synopsis
Let a project consist of two installable libraries and a binary
(@file{ltb2}) linked to both of them. One of the libraries depends on
an external library, which has a libtool archive installed along with
the shared library. The figure below illustrates this scheme:
@example
@group
ltb2 <---+-- liba <==== @file{@var{libdir}}/libdep.la
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+-- libb
@end group
@end example
Then, for GNU/Linux systems the wrapper script would issue the relink
command that ends with the following options (split along multiple
lines for readability):
@example
-Wl,-rpath -Wl,@var{srcdir}/liba/.libs
-Wl,-rpath -Wl,@var{libdir}
-Wl,-rpath -Wl,@var{srcdir}/libb/.libs
-Wl,-rpath -Wl,@var{libdir}
@end example
For FreeBSD, the @env{LD_LIBRARY_PATH} used by the wrapper will look
like:
@example
@var{srcdir}/liba/.libs:@var{libdir}:@var{srcdir}/libb/.libs:$LD_LIBRARY_PATH
@end example
In both cases, the @file{@var{libdir}} directory appearing before
@file{libb} will cause the @file{libb} library to be searched in
@file{@var{libdir}} first. If a prior version of the project is
installed in the same prefix as the @file{libdep} library, then the
@command{ltb2} wrapper will use the version of @file{liba} from the
local source tree, but the version of @file{libb} installed on the
system.
@unnumbered Background
The issue was initially discovered when building @uref{https://mailutils.org,GNU
mailutils} on FreeBSD with support for OpenLDAP enabled. The latter
incurred dependency on @file{libldap}, which was installed (along with
@file{libldap.la}) in @file{/usr/local/lib}.
The package built in these conditions failed most tests because it was
using mailutils libraries from prior version, installed in
@file{/usr/local/lib}.
The issue has been confirmed to exist on GNU/Linux as well
(@pxref{affected systems}).
@unnumbered The test case
A minimal testcase is available for download from
@uref{ltbug-2.tar.gz}. It consists of two subpackages:
@file{ltb2dep} implementing the dependency library, and the main
test package @file{ltb2}. The latter builds and installs two libraries:
@file{liba} and @file{libb}, and a test program @command{ltb2}, linked
with both of these. The @file{liba} library provides the function
@samp{ltb2a_version}. The @file{libb} library implements a similar
function @samp{ltb2b_version}. Both functions print on the standard
output the value of the @samp{LTBUG_ID} macro defined at the compile
time. The @command{ltb2} program calls both functions in order.
The test script first builds and installs the dependency library
@file{ltb2dep}. Then, it builds the package with
@code{LTBUG_ID="installed"} and installs it. When run, the installed
@command{ltb2} program will output
@example
ltb2a: installed
ltb2b: installed
@end example
Finally, the test rebuilds the package with @code{LTBUG_ID="local"}
and runs the @command{ltb2} program from the source tree. The program
then outputs:
@example
ltb2a: local
ltb2b: installed
@end example
@noindent
This shows that the command uses @file{libltb2a} from the local source
tree and @file{libltb2b} previously installed on the system.
Follow these steps to run the test:
@enumerate 1
@item Unpack the archive
@example
tar xf ltbug-2.tar.gz
@end example
@item Run
@example
sh ltbug-2/test.sh
@end example
@noindent
or
@example
make -C ltbug-2 check
@end example
@end enumerate
If the bug is present, you will see the following output:
@example
Building dependency library
Building and installing project
Building local copy of the project
Running test program
Test failed:
--- expout 2019-12-12 13:45:53.193782824 +0200
+++ stdout 2019-12-12 13:45:53.222782826 +0200
@@ -1,2 +1,2 @@
ltb2a: local
-ltb2b: local
+ltb2b: installed
Keeping the directories in place. When no longer needed, run:
rm -rf /tmp/ltb-test2
rm -rf ltb-test2
make: *** [check] Error 1
@end example
The directory @file{ltb-test2} will be left on disk for examination.
It will contain:
@table @file
@item build_dep
Build directory for the dependency library @file{libltb2dep}.
@item build_inst
A directory where the installed version of the package was built.
@item build_local
Local build directory. The test runs @command{build_local/src/ltb2}.
@item expout
Expected standard output.
@item stdout
Obtained standard output.
@item ltb2.out
Standard output generated by the build process.
@item ltb2.err
Standard output generated by the build process.
@end table
The test script takes the same command line options as described above
for the @file{ltb1} test.
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