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NOTES.UNIX: add "Linking your application" paragraph

... and mention more runtime search path flags.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6587)
tags/OpenSSL_1_1_1-pre9
Andy Polyakov 1 year ago
parent
commit
2c879241ba
1 changed files with 35 additions and 9 deletions
  1. 35
    9
      NOTES.UNIX

+ 35
- 9
NOTES.UNIX View File

@@ -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.

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