Build error in mod_proxy_protocol on Alpine

[nvmker]

Hi,
I've tried to build latest versions of proftpd and mod_proxy_protocol(both are cloned from github several minutes ago), and got a build error.

Here is output:

 ../libtool --mode=compile --tag=CC gcc -DHAVE_CONFIG_H  -DLINUX  -I.. -I../include -I../include -I/usr/include/libxml2 -I/usr/include/mysql -g2 -O2 -Wall -fno-omit-frame-pointer -Werror=implicit-function-declaration -DPR_SHARED_MODULE -c ../modules/mod_proxy_protocol.c
libtool: compile:  gcc -DHAVE_CONFIG_H -DLINUX -I.. -I../include -I../include -I/usr/include/libxml2 -I/usr/include/mysql -g2 -O2 -Wall -fno-omit-frame-pointer -Werror=implicit-function-declaration -DPR_SHARED_MODULE -c ../modules/mod_proxy_protocol.c  -fPIC -DPIC -o .libs/mod_proxy_protocol.o
../modules/mod_proxy_protocol.c: In function 'readv_sock':
../modules/mod_proxy_protocol.c:200:9: error: implicit declaration of function 'readv' [-Werror=implicit-function-declaration]
   res = readv(sockfd, iov, count);
         ^~~~~
cc1: some warnings being treated as errors
make[1]: *** [Makefile:34: mod_proxy_protocol.la] Error 1
make[1]: Leaving directory '/usr/local/proftpd/modules'
make: *** [Makefile:40: modules] Error 2

Configure command is:

./configure '--program-prefix=' '--disable-dependency-tracking' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc' '--datadir=/usr/share' '--includedir=/usr/include' '--libexecdir=/usr/libexec/proftpd' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--localstatedir=/var/run/proftpd' '--disable-auth-pam' '--disable-strip' '--enable-dso' '--enable-facl' '--disable-ipv6' '--enable-nls' '--enable-openssl' '--enable-ctrls' '--enable-pcre' '--enable-autoshadow' '--enable-tunable-buffer-size' '--enable-sendfile' '--enable-ipv6' '--enable-dso' '--with-libraries=/usr/lib' '--with-includes=/usr/include/mysql' '--with-includes=/usr/include/libxml2' '--with-modules=mod_aws:mod_readme:mod_dynmasq' '--with-shared=mod_wrap2:mod_wrap2_file:mod_wrap2_sql:mod_sql:mod_sql_passwd:mod_sql_mysql:mod_ban:mod_facl:mod_rewrite:mod_site_misc:mod_ifversion:mod_dnsbl:mod_qos:mod_sftp:mod_sftp_sql:mod_ifsession:mod_quotatab:mod_quotatab_file:mod_quotatab_sql:mod_exec:mod_digest:mod_geoip:mod_statcache:mod_proxy_protocol'

[Castaglia]

Interesting. On what platform are you building? That is, what do the following commands show?

$ uname -a
$ cat /etc/lsb-release

I've not encountered this build error locally, nor did the Travis CI builds. Thus I'm wondering if it's a difference in the system header layout, for a relatively new/different distro...

[nvmker]

It's a alpine 3.6, I've sent Dockerfile to your email.

[Castaglia]

Thanks! Using that, I was able to reproduce the problem. On Alpine, the readv(2) function is declared via sys/uio.h, which must be explicitly included.

[Castaglia]

Fixed in master. Thanks!