-D_FORTIFY_SOURCE=2 is enable in gcc by default on alpine. See the
010_all_default-fortify-source.patch patch in main/gcc. Disabling
it here silences a bunch of compiler warnings.

diff -upr vis-0.2.orig/configure vis-0.2/configure
--- vis-0.2.orig/configure	2016-04-06 23:36:44.232477390 +0200
+++ vis-0.2/configure	2016-04-06 23:36:59.705671155 +0200
@@ -199,7 +199,7 @@ tryflag   CFLAGS_TRY  -Werror=unused-com
 tryldflag LDFLAGS_TRY -Werror=unknown-warning-option
 tryldflag LDFLAGS_TRY -Werror=unused-command-line-argument
 
-CFLAGS_STD="-std=c99 -D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -DNDEBUG -D_FORTIFY_SOURCE=2"
+CFLAGS_STD="-std=c99 -D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -DNDEBUG"
 LDFLAGS_STD="-lc"
 
 OS=$(uname)
