Undefined reference to SSL_library_init and SSL_load_error_strings

Question

I am implementing a OpenSSL code and have already included required header files but still I am getting errors like *

undefined reference to SSL_library_init

I guess it's a linking error rather than a compilation error.

I am implementing it in Linux box using slickeditor.

And how are you invoking the linker? Are you instructing it to link against the OpenSSL library, such as with -lcrypto for gcc? — rlibby
– rlibby, Commented Apr 8, 2011 at 10:21
nope. the machine I got already has openssl. when I do which openssl it shows be path like /usr/bin/openssl. So the next step I did was to include header files in my existing code and then in slickeditor property i i tried to include -llibeay32 and -lssleay32. But no joy — samprat
– samprat, Commented Apr 8, 2011 at 10:25
The OpenSSL library is called libcrypto. Link to it with with -lcrypto. I don't know anything about SlickEdit. Is it invoking the compiler and linker for you, is that done in a makefile, or do you do it on a command line? Somehow you need to tell the linker to link to libcrypto. For invoking gcc on the command line, this means adding the option -lcrypto. — rlibby
– rlibby, Commented Apr 8, 2011 at 10:30
Apologies, SSL_library_init is in libssl, so the link option would be -lssl. ldd $(which openssl) will show you how your openssl is linked and where those libraries are. If it still doesn't work, perhaps that directory is not on the path for the linker. You can add that path with -Lpath, such as -L/lib/ — rlibby
– rlibby, Commented Apr 8, 2011 at 10:42
You should get a minimal test case working on the command line. #include "whatever" \n int main(void) { SSL_library_init(blah, blah, blah); return 0; } and then g++ my_minimal_test_case.c++ -lssl. If this works then you don't understand your editor/IDE. If it doesn't then you have some configuration issue. — rlibby
– rlibby, Commented Apr 8, 2011 at 11:08

jww · Accepted Answer · 2015-01-13 18:14:42Z

35

Link against libssl and libcrypto. Your LDFLAGS and LDLIBS would be as follows. Order matters for LDLIBS:

LDFLAGS = -L/usr/local/ssl/lib
LDLIBS = -lssl -lcrypto

Don't worry about adding the "lib" in front of library name, or the "so" or "a" suffix. The linker will do it for you.

If you are building from the command line, then you would use the following. Again, order matters.

gcc foo.c -o foo.exe -L/usr/local/ssl/lib -lssl -lcrypto

If you are using the system's OpenSSL, then you can omit -L/usr/local/ssl/lib.

edited Jan 13, 2015 at 18:14

answered Dec 2, 2013 at 7:50

jww

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2 Comments

Craig Scott Over a year ago

According to comments on the question, SSL_library_init is in libssl, so shouldn't the correct order be LDLIBS = -lcrypto -lssl instead?

jww Over a year ago

@CraigScott - Sorry about the late reply. Order matters because its a single pass linker. When LD encounters unsatisfied link symbols, it notes them and looks for them in libraries that follow. If libcrypto was first, then libssl would have unsatisfied symbols like BN_new because libcrypto needs to follow libssl to satisfy the missing symbols. The other option is a two-pass linker. Sometimes you will also see something like -la -lb -la (liba followed by libb followed by liba). Its usually due to a circular reference lurking behind the scenes.

rogerdpack · Accepted Answer · 2018-07-12 00:24:50Z

12

For me this meant to install

 apt install libssl1.0-dev

answered Jul 12, 2018 at 0:24

rogerdpack

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2 Comments

Rick Sanchez Over a year ago

You're a lifesaver. Was trying to compile AOSP on Ubuntu 18, and had to downgrade openssl 1.1 -> 1.0.1 , but had installed libssl-dev

Brent Writes Code Over a year ago

High five to both of you. I had the same issue and the combination of these two comments made me realize it.

unDEFER · Accepted Answer · 2020-04-15 14:15:52Z

8

These methods are deprecated in OpenSSL 1.1. You don't need to use it more. You can just remove it. More info in OpenSSL manual.

answered Apr 15, 2020 at 14:15

unDEFER

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Comments

Ladislav Vašina · Accepted Answer · 2022-09-29 16:24:46Z

1

Simply add -lssl -lcrypto to your Makefile and it should work.

Example of Makefile:

foo: foo.o
g++ -std=c++17 -o foo foo.cpp -lcrypto -lssl

answered Sep 29, 2022 at 16:24

Ladislav Vašina

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Michael Popovich · Accepted Answer · 2017-03-17 19:14:03Z

0

ldd libssl.so -> libcrypto.so.1.1 => not found

sudo ln -s /usr/local/lib64/libcrypto.so.1.1 /usr/lib64/libcrypto.so.1.1

libcrypto.so.1.1 => /lib64/libcrypto.so.1.1 (0x00007f17d46c7000)

answered Mar 17, 2017 at 19:14

Michael Popovich

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