From 2c879241baaf9115e8ebbe228e1a624564eea64c Mon Sep 17 00:00:00 2001 From: Andy Polyakov Date: Fri, 22 Jun 2018 14:13:59 +0200 Subject: [PATCH] NOTES.UNIX: add "Linking your application" paragraph ... and mention more runtime search path flags. Reviewed-by: Rich Salz Reviewed-by: Richard Levitte (Merged from https://github.com/openssl/openssl/pull/6587) --- NOTES.UNIX | 44 +++++++++++++++++++++++++++++++++++--------- 1 file changed, 35 insertions(+), 9 deletions(-) diff --git a/NOTES.UNIX b/NOTES.UNIX index 284da105c..6c291cbab 100644 --- a/NOTES.UNIX +++ b/NOTES.UNIX @@ -24,12 +24,12 @@ 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. @@ -42,14 +42,15 @@ 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 @@ -89,3 +90,28 @@ $ ./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.