% make
gcc -Wall -pedantic -Wextra -std=gnu99 -I../lib -I./ -Ioutput_modules -O2 -g -Wall  -g -O2  -D_FORTIFY_SOURCE=2 -fstack-protector-all -fwrapv -fPIC --param ssp-buffer-size=1 -Wall -fno-strict-aliasing -W -Wfloat-equal -Wundef -Wpointer-arith -Wwrite-strings -Wredundant-decls -Wchar-subscripts -Wcomment -Wformat=2 -Wwrite-strings -Wredundant-decls -Wno-unused-but-set-variable -Wnested-externs -Wbad-function-cast -Winit-self -Wmissing-field-initializers -Waddress -Wmissing-noreturn -Wnormalized=id -Woverride-init -Wstrict-overflow=1 -Wextra -Warray-bounds -Wstack-protector -Wformat -Wformat-security -Wpointer-sign -Wno-format-nonliteral -Wno-format-y2k -Werror   -c -o constraint.o ../lib/constraint.c
<command-line>:0:0: error: "_FORTIFY_SOURCE" redefined [-Werror]
../lib/constraint.c:1:0: note: this is the location of the previous definition
cc1: all warnings being treated as errors
make: *** [constraint.o] Error 1

diff --git a/src/Makefile b/src/Makefile
index 72eb0d5..e35c4ab 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -24,7 +24,7 @@ GCCWARNINGS = -Wall -fno-strict-aliasing -W -Wfloat-equal -Wundef      \
 -Waddress -Wmissing-noreturn -Wnormalized=id    \
 -Woverride-init -Wstrict-overflow=1 -Wextra -Warray-bounds             \
 -Wstack-protector -Wformat -Wformat-security -Wpointer-sign -Wno-format-nonliteral -Wno-format-y2k
-GCCHARDENING=-D_FORTIFY_SOURCE=2 -fstack-protector-all -fwrapv -fPIC --param ssp-buffer-size=1
+GCCHARDENING=-fstack-protector-all -fwrapv -fPIC --param ssp-buffer-size=1
 LDHARDENING=-z relro -z now

 EXTRACFLAGS=-g -O2 $(EXTRA_CFLAGS) $(GCCHARDENING) $(GCCWARNINGS) -Werror