Linking OpenSSL into a dynamic library - c++

Question

I'm trying to static link OpenSSL into my program.
It works fine when linking into the executable. I need to use OpenSSL in a shared library (so, or dll) that I dynamically load later on when the process executes.
Trying to statically link OpenSSL into the shared library causes errors due to OpenSSL not being compiled with -fPIC. Is it possible to do this without recompiling openssl?
Also, is there a better way to do this?

Answer 1

I'm trying to static link OpenSSL into my program.
In this case, its as simple as:
gcc prog.c /usr/local/lib/libssl.a /usr/local/lib/libcrypto.a -o prog.exe -ldl
It works fine when linking into the executable.
Devil's advocate... Does it work fine with Position Independent Code (PIE)? PIE on a program is the equivalent to PIC on a shared object (some hand waiving).
gcc -fPIE prog.c /usr/local/lib/libssl.a /usr/local/lib/libcrypto.a -o prog.exe -ldl
According to the GCC folks, you can compile with fPIC, and then build a shared object with -fPIC or a relocatable executable with -fPIE. That is, its OK to use -fPIC for both.
Trying to statically link OpenSSL into the shared library causes errors due to OpenSSL not being compiled with -fPIC.
That's easy enough to fix. You simply specify shared in configure:
./config shared no-ssl2 no-ssl3 no-comp --openssldir=/usr/local/ssl
make
sudo make install
I think you can also (notice the lack of shared):
export CFLAGS="-fPIC"
./config no-ssl2 no-ssl3 no-comp --openssldir=/usr/local/ssl
make
sudo make install
not being compiled with -fPIC. Is it possible to do this without recompiling openssl?
NO, you have to compile with PIC to ensure GCC generates relocatable code.
Also, is there a better way to do this?
Usually you just configure with shared. That triggers -fPIC, which gets you relocatable code.
There's other things you can do, but they are more intrusive. For example, you can modify Configure line (like linux-x86_64), and add -fPIC in the second field. The fields are separated by colons, and the second field is $cflags used by the OpenSSL build system.
You can see an example of modifying Configure at Build OpenSSL with RPATH?