NOTES.UNIX: add "Linking your application" paragraph
... and mention more runtime search path flags.
Every Unix system has its own set of default locations for shared
libraries, such as /lib, /usr/lib or possibly /usr/local/lib. If
libraries are installed in non-default locations, dynamically linked
- binaries will not find them and therefore fail to run unless they get a
- bit of help from a defined runtime shared library search path.
+ binaries will not find them and therefore fail to run, unless they get
+ a bit of help from a defined runtime shared library search path.
For OpenSSL's application (the 'openssl' command), our configuration
scripts do NOT generally set the runtime shared library search path for
- you. It's therefore advisable to set it explicitly when configuring
+ you. It's therefore advisable to set it explicitly when configuring,
unless the libraries are to be installed in directories that you know
to be in the default list.
Possible options to set the runtime shared library search path include
the following:
- -Wl,-rpath,/whatever/path
- -R /whatever/path
- -rpath /whatever/path
+ -Wl,-rpath,/whatever/path # Linux, *BSD, etc.
+ -R /whatever/path # Solaris
+ -Wl,-R,/whatever/path # AIX (-bsvr4 is passed internally)
+ -Wl,+b,/whatever/path # HP-UX
+ -rpath /whatever/path # Tru64, IRIX
OpenSSL's configuration scripts recognise all these options and pass
- them to the Makefile that they build. (In fact, it recognises anything
- starting with '-Wl,' as a linker option, so for example, HP-UX'
- '-Wl,+b,/whatever/path' would be used correctly)
+ them to the Makefile that they build. (In fact, all arguments starting
+ with '-Wl,' are recognised as linker options.)
Please do not use verbatim directories in your runtime shared library
search path! Some OpenSSL config targets add an extra directory level
$ ./config --prefix=/usr/local/ssl --openssldir=/usr/local/ssl \
'-Wl,--enable-new-dtags,-rpath,$(LIBRPATH)'
+
+ It might be worth noting that some/most ELF systems implement support
+ for runtime search path relative to the directory containing current
+ executable, by interpreting $ORIGIN along with some other internal
+ variables. Consult your system documentation.
+
+ Linking your application
+ ------------------------
+
+ Third-party applications dynamically linked with OpenSSL (or any other)
+ shared library face exactly the same problem with non-default locations.
+ The OpenSSL config options mentioned above might or might not have bearing
+ on linking of the target application. "Might" means that under some
+ circumstances it would be sufficient to link with OpenSSL shared library
+ "naturally", i.e. with -L/whatever/path -lssl -lcrypto. But there are
+ also cases when you'd have to explicitly specify runtime search path
+ when linking your application. Consult your system documentation and use
+ above section as inspiration...
+
+ Shared OpenSSL builds also install static libraries. Linking with the
+ latter is likely to require special care, because linkers usually look
+ for shared libraries first and tend to remain "blind" to static OpenSSL
+ libraries. Referring to system documentation would suffice, if not for
+ a corner case. On AIX static libraries (in shared build) are named
+ differently, add _a suffix to link with them, e.g. -lcrypto_a.
