--- Makefile.orig	2019-03-15 16:38:36 UTC
+++ Makefile
@@ -15,7 +15,8 @@ endif
 
 # Compiler flags for various configurations:
 
-CFLAGS := -std=c99 -pedantic -Wall -Wextra -Wno-unused-parameter
+# change to c11 on FreeBSD because FreeBSD headers induce c11 through isnan(3), etc.
+CFLAGS := -std=c11 -pedantic -Wall -Wextra -Wno-unused-parameter
 
 ifeq "$(CC)" "clang"
   CFLAGS += -Wunreachable-code
@@ -31,7 +32,7 @@ else ifeq "$(build)" "sanitize"
   CFLAGS += -pipe -g -fsanitize=address -fno-omit-frame-pointer
   LDFLAGS += -fsanitize=address
 else
-  CFLAGS += -Os
+  CFLAGS += -O3 # use -O3 on FreeBSD instead of -Os because this isn't an embedded platform
   LDFLAGS += -Wl,-s
 endif