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Re: Build in mingw for libcurl with OpenSSL and HTTP2 support fails with "undefined reference to 'sk_num'" in openssl.c

From: Ray Satiro via curl-library <>
Date: Wed, 22 Mar 2017 15:03:34 -0400

On 3/22/2017 11:59 AM, Reese Grimsley wrote:
> I built nghttp2 and openssl (1.1.0e), and ran ./configure in the
> mingw32 shell of msys2. The output from configure told me that openssl
> and http2 were both enabled. When calling make, it shows CC
> libcurl_la-foo.lo for a number of files (~50), and then gets down to
> the line "CCLD <>", and fails here. I get
> about 15 messages stating an undefined reference (e.g.
> vtls/.libs/libcurl_la-openssl.o:openssl.c:(.text+0xbda): undefined
> reference to '|sk_num' OR
> vtls/.libs/libcurl_la-openssl.o:openssl.c:(.text+0x48f9): undefined
> reference to '|ERR_free_strings'). Following these lines are the
> actual error messages:
> vtls/.libs/libcurl_la-openssl.o:openssl.c:(.text+0x4912): undefined
> reference to 'SSL_COMP_free_compression_methods'

There was an issue with that but it was fixed last year [1]. Since you
are building 7.53.1 I can only guess that some earlier version of
OpenSSL includes was used, since libcurl only calls that function in
certain 1.0.2 versions [2]. You may need to specify
--with-ssl=/your/ssl/dir or set PKG_CONFIG_LIBDIR. You should be able to
see in the configure output what version it detects, it will look like this:

checking for OpenSSL headers version... 1.0.2 - 0x100020bfL
checking for OpenSSL library version... 1.0.2
checking for OpenSSL headers and library versions matching... yes


Received on 2017-03-22