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

From: Reese Grimsley <>
Date: Wed, 22 Mar 2017 10:59:21 -0500

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'
collect2.exe: error: ld returned 1 exit status
make[2]: *** [Makefile:893:] Error 1
make[2]: Leaving directory '/c/curl2/curl-7.53.1/lib'
make[1]: *** [Makefile:734: all] Error 2
make[1]: Leaving directory '/c/curl2/curl-7.53.1/lib'
make: *** [Makefile:893: all-recursive] Error 1

I am building curl/libcurl version 7.53.1 on Windows 10 (64-bit) using
msys2 for mingw32 build. Looking through the openssl.c file in question, a
few of the "undefined references" are in fact in the in the file, but there
are no instances of sk_num, sk_value, or sk_pop_free which the make command
determines as undefined references. Any idea what is wrong here? Thanks,
let me know if I should ask this question elsewhere

Received on 2017-03-22