Arch Linux

Just a thought... are you using the current PKGBUILD or an old version? I recently updated it with a fix for building with GCC 5.x

#########################################################################
# ARCHITECTURE, COMPILE FLAGS
#########################################################################
#
CARCH="x86_64"
CHOST="x86_64-unknown-linux-gnu"

#-- Compiler and Linker Flags
# -march (or -mcpu) builds exclusively for an architecture
# -mtune optimizes for an architecture, but builds for whole processor family
CPPFLAGS="-D_FORTIFY_SOURCE=2"
CFLAGS="-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong --param=ssp-buffer-size=4"
CXXFLAGS="-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong --param=ssp-buffer-size=4"
LDFLAGS="-Wl,-O1,--sort-common,--as-needed,-z,relro"
#-- Make Flags: change this for DistCC/SMP systems
MAKEFLAGS="-j3"

Just using x86_64-unknown-linux-gnu. I changed it back to -O2 and now I'm getting a slightly different build failure.

==> Starting build()...
gcc -g -ggdb -Wall -O3 -c src/rawsock-arp.c -o tmp/rawsock-arp.o
gcc -g -ggdb -Wall -O3 -c src/proto-tcp-telnet.c -o tmp/proto-tcp-telnet.o
gcc -g -ggdb -Wall -O3 -c src/xring.c -o tmp/xring.o
In file included from src/xring.c:4:0:
src/string_s.h:94:3: error: #error unknown compiler
# error unknown compiler
^
src/xring.c: In function ‘xring_selftest’:
src/xring.c:199:52: error: expected ‘)’ before ‘PRIu64’
printf("xring: selftest failed with %" PRIu64 "\n", result);
^
src/xring.c:199:20: warning: spurious trailing ‘%’ in format [-Wformat=]
printf("xring: selftest failed with %" PRIu64 "\n", result);
^
In file included from src/rawsock-arp.c:17:0:
src/string_s.h:94:3: error: #error unknown compiler
# error unknown compiler
^
Makefile:87: recipe for target 'tmp/xring.o' failed
make: *** [tmp/xring.o] Error 1
make: *** Waiting for unfinished jobs....
Makefile:87: recipe for target 'tmp/rawsock-arp.o' failed
make: *** [tmp/rawsock-arp.o] Error 1
==> ERROR: A failure occurred in build().
Aborting...

It builds for me. What compiler are you using?

==> Starting build()...
gcc -g -ggdb -Wall -O3 -c src/proto-imap4.c -o tmp/proto-imap4.o
gcc -g -ggdb -Wall -O3 -c src/rawsock-pcapfile.c -o tmp/rawsock-pcapfile.o
gcc -g -ggdb -Wall -O3 -c src/rawsock-arp.c -o tmp/rawsock-arp.o
In file included from src/rawsock-arp.c:17:0:
src/string_s.h:94:3: error: #error unknown compiler
# error unknown compiler
^
Makefile:87: recipe for target 'tmp/rawsock-arp.o' failed
make: *** [tmp/rawsock-arp.o] Error 1
make: *** Waiting for unfinished jobs....
==> ERROR: A failure occurred in build().
Aborting...

Hey, thanks for the package... after looking at it I have some small improvements:
- please add provices=('masscan') and conflicts=('masscan')
- always use quotes when using ${pkgdir}
- no need to gzip mangpages yourself, will be done automatically if placed without .gz extension at "${pkgdir}/usr/share/man/man8/masscan.8"
- there is a regression test that you can call in check() via 'make test'

Fixed build with GCC 5.x