How to cross compile CURL library with SSL and ZLIB support
21 Aug 2014 
Matteo Mattei 
linux embedded curl 
Every time I have to cross compile a new application or library it is always painful and I often have to spend several minutes (hours) to figure out how to build it. In this case I am going to show you how to cross compile CURL library (and application) with SSL and ZLIB support for an embedded system based on ARM.
First of all I suppose you already have all includes and libraries (static and dynamic) of openSSL and Zlib somewhere in your system (how to cross-compile openssl and zlib is out of the scope of this post).
In my case I have this structure:
.
├── openssl
│ ├── apps
│ │ └── openssl
│ ├── include
│ │ └── openssl
│ │ ├── aes.h
│ │ ├── asn1.h
│ │ ├── asn1_mac.h
│ │ ├── asn1t.h
│ │ ├── bio.h
│ │ ├── blowfish.h
│ │ ├── bn.h
│ │ ├── buffer.h
│ │ ├── camellia.h
│ │ ├── cast.h
│ │ ├── cmac.h
│ │ ├── cms.h
│ │ ├── comp.h
│ │ ├── conf_api.h
│ │ ├── conf.h
│ │ ├── crypto.h
│ │ ├── des.h
│ │ ├── des_old.h
│ │ ├── dh.h
│ │ ├── dsa.h
│ │ ├── dso.h
│ │ ├── dtls1.h
│ │ ├── ebcdic.h
│ │ ├── ecdh.h
│ │ ├── ecdsa.h
│ │ ├── ec.h
│ │ ├── engine.h
│ │ ├── e_os2.h
│ │ ├── err.h
│ │ ├── evp.h
│ │ ├── hmac.h
│ │ ├── idea.h
│ │ ├── krb5_asn.h
│ │ ├── kssl.h
│ │ ├── lhash.h
│ │ ├── md4.h
│ │ ├── md5.h
│ │ ├── mdc2.h
│ │ ├── modes.h
│ │ ├── objects.h
│ │ ├── obj_mac.h
│ │ ├── ocsp.h
│ │ ├── opensslconf.h
│ │ ├── opensslv.h
│ │ ├── ossl_typ.h
│ │ ├── pem2.h
│ │ ├── pem.h
│ │ ├── pkcs12.h
│ │ ├── pkcs7.h
│ │ ├── pqueue.h
│ │ ├── rand.h
│ │ ├── rc2.h
│ │ ├── rc4.h
│ │ ├── ripemd.h
│ │ ├── rsa.h
│ │ ├── safestack.h
│ │ ├── seed.h
│ │ ├── sha.h
│ │ ├── srp.h
│ │ ├── srtp.h
│ │ ├── ssl23.h
│ │ ├── ssl2.h
│ │ ├── ssl3.h
│ │ ├── ssl.h
│ │ ├── stack.h
│ │ ├── symhacks.h
│ │ ├── tls1.h
│ │ ├── ts.h
│ │ ├── txt_db.h
│ │ ├── ui_compat.h
│ │ ├── ui.h
│ │ ├── whrlpool.h
│ │ ├── x509.h
│ │ ├── x509v3.h
│ │ └── x509_vfy.h
│ └── libs
│ ├── lib4758cca.so
│ ├── libaep.so
│ ├── libatalla.so
│ ├── libcapi.so
│ ├── libchil.so
│ ├── libcrypto.a
│ ├── libcrypto.so
│ ├── libcrypto.so.1.0.0
│ ├── libcswift.so
│ ├── libgmp.so
│ ├── libgost.so
│ ├── libnuron.so
│ ├── libpadlock.so
│ ├── libssl.a
│ ├── libssl.so
│ ├── libssl.so.1.0.0
│ ├── libsureware.so
│ └── libubsec.so
└── zlib
├── include
│ ├── zconf.h
│ └── zlib.h
└── libs
├── libz.a
├── libz.so -> libz.so.1.2.8
├── libz.so.1 -> libz.so.1.2.8
└── libz.so.1.2.8
Now download the last version of CURL, decompress and configure it:
$ wget http://curl.haxx.se/download/curl-7.37.1.tar.gz
$ tar xzf curl-7.37.1.tar.gz
$ export ROOTDIR="${PWD}"
$ cd curl-7.37.1/
$ export CROSS_COMPILE="arm-none-linux-gnueabi"
$ export CPPFLAGS="-I${ROOTDIR}/openssl/include -I${ROOTDIR}/zlib/include"
$ export LDFLAGS="-L${ROOTDIR}/openssl/libs -L${ROOTDIR}/zlib/libs"
$ export AR=${CROSS_COMPILE}-ar
$ export AS=${CROSS_COMPILE}-as
$ export LD=${CROSS_COMPILE}-ld
$ export RANLIB=${CROSS_COMPILE}-ranlib
$ export CC=${CROSS_COMPILE}-gcc
$ export NM=${CROSS_COMPILE}-nm
$ export LIBS="-lssl -lcrypto"
$ ./configure --prefix=${ROOTDIR}/build --target=${CROSS_COMPILE} --host=${CROSS_COMPILE} --build=i586-pc-linux-gnu --with-ssl --with-zlib
At the end of the configure you should see a configuration resume similar to the following:
curl version: 7.37.1
Host setup: arm-none-linux-gnueabi
Install prefix: /tmp/working_copy/build
Compiler: arm-none-linux-gnueabi-gcc
SSL support: enabled (OpenSSL)
SSH support: no (--with-libssh2)
zlib support: enabled
GSS-API support: no (--with-gssapi)
SPNEGO support: no (--with-spnego)
TLS-SRP support: enabled
resolver: default (--enable-ares / --enable-threaded-resolver)
ipv6 support: no (--enable-ipv6)
IDN support: no (--with-{libidn,winidn})
Build libcurl: Shared=yes, Static=yes
Built-in manual: enabled
--libcurl option: enabled (--disable-libcurl-option)
Verbose errors: enabled (--disable-verbose)
SSPI support: no (--enable-sspi)
ca cert bundle: no
ca cert path: no
LDAP support: no (--enable-ldap / --with-ldap-lib / --with-lber-lib)
LDAPS support: no (--enable-ldaps)
RTSP support: enabled
RTMP support: no (--with-librtmp)
metalink support: no (--with-libmetalink)
HTTP2 support: disabled (--with-nghttp2)
Protocols: DICT FILE FTP FTPS GOPHER HTTP HTTPS IMAP IMAPS POP3 POP3S RTSP SMTP SMTPS TELNET TFTP
Now compile and install it in the previously configured build directory:
$ make
$ make install
Now in the parent directory you should have a new folder called build with the new curl library and application with OpenSSL and Zlib support cross compiled for ARM:
build/
├── bin
│ ├── curl
│ └── curl-config
├── include
│ └── curl
│ ├── curlbuild.h
│ ├── curl.h
│ ├── curlrules.h
│ ├── curlver.h
│ ├── easy.h
│ ├── mprintf.h
│ ├── multi.h
│ ├── stdcheaders.h
│ └── typecheck-gcc.h
└── lib
├── libcurl.a
├── libcurl.la
├── libcurl.so -> libcurl.so.4.3.0
├── libcurl.so.4 -> libcurl.so.4.3.0
├── libcurl.so.4.3.0
└── pkgconfig
└── libcurl.pc
(I voluntary omitted the share folder in the tree exploded).