improve build and release flags: g3, O2/Og, D_FORTIFY_SOURCE=2, Wpeda…

…ntic, etc

Makefile

@@ -13,10 +13,21 @@ bindir   = $(prefix)/bin
 
 all: release
 
-debug: CFLAGS += -g -O0 -Wall -Wextra
+# DEBUG Build
+# Add several compile- and run-time checks, warnings and preventions (Buffer Overflow, etc)
+# -g3: Adds debugging information, level 3 (default for -g is level 2)
+# -Og: Enables optimizations that do not interfere with debugging
+# -Wall: Enables all the warnings about constructions that some users consider questionable, and that are easy to avoid
+# -Wextra: Enables some extra warning flags that are not enabled by -Wall
+debug: CFLAGS += -g3 -Og -Wall -Wextra -Wpedantic -D_FORTIFY_SOURCE=2
 debug: clean $(TARGET)
 
-release: CFLAGS += -s
+# RELEASE Build
+# Stripped binary, maximum optimization
+# -s: Strip executable (remove all symbol table and relocation information)
+# -O2: Optimize level 2 and activate default FORTIFY_SOURCE=2 in most setups
+# -D_FORTIFY_SOURCE=2: explicitely enable additional compile-time and run-time checks for several libc functions
+release: CFLAGS += -s -O2 -D_FORTIFY_SOURCE=2
 release: clean $(TARGET)
 
 $(TARGET): $(SOURCES) $(HEADERS)