Updated README.md to show how `FEATURE` flags are defined and used now.

Fortune for sink's current commit: Great curse − 大凶

Makefile

@@ -19,7 +19,7 @@
 # * `STRIP` - Strip command for default output (stripped release) target (`make sink`). set `make STRIP=:` to prevent stripping entirely. (NOTE: When using `make install`, `STRIP=:` will not work, instead, paradoxically, set `STRIP=true`, they have the same effect for all targets)
 PROJECT=sink
 DESCRIPTION=sink all input and output of a program to /dev/null
-VERSION=0.1.0
+VERSION=0.2.0
 AUTHOR=Avril <avril@cumallover.me>
 LICENSE=GPL3+
 

README.md

@@ -19,11 +19,15 @@ Run `make && sudo make install` to build with full optimisations and install `si
 
 To build for debugging, run `make debug`. 
 
-### Compiler flags
+### Feature flags
-* `-DREPLACE_STDERR` - Add to `CFLAGS` when building a target to re-route the child program's `stderr` stream to the sink as well. By default, it is passed through as default.
+
-* `-DNO_SEARCH_PATH` - Add to `CFLAGS` when building to prevent the program looking up its argument in the `PATH` environment variable.
+Set the following to the environment variable `FEATURES` when invoking `make` to build with the speficied features' behaviour (e.g. `FEATURES=NO_SEARCH_PATH\ NO_ENV make`.)
-* `-DNO_ENV` - Add to `CFLAGS` when building to prevent `envp` passthrough to the `execve()`'d program.
+When a debug-mode splash screen is printed, the features the binary was compiled with are also printed.
-* `-DDEBUG_IGNORE_SPLASH` - Do not print project and version info in debug builds on startup.
+
+* `REPLACE_STDERR` - Re-route the child program's `stderr` stream to the sink as well. By default, it is passed through as default.
+* `NO_SEARCH_PATH` - Prevent the program looking up its argument in the `PATH` environment variable.
+* `NO_ENV` - Prevent `envp` passthrough to the `execve()`'d program.
+* `DEBUG_IGNORE_SPLASH` - Do not print project and version info in debug builds on startup.
 
 ### Installation
 The program must have been built before installation, and installation and uninstallation must be done as root.

sink.c

@@ -8,7 +8,8 @@
 
 #include "comp_features.h"
 
-static const enum compiled_features compiled_features = FEATURE_FLAGS;
+__attribute__((used)) // For loading debug binary symbol
+const enum compiled_features sink_compiled_features = FEATURE_FLAGS;
 
 #define r_stdin 0
 #define r_stdout 1
@@ -153,6 +154,7 @@ static inline size_t count_list(const void*const* p)
 	while(*p++) n+=1;
 	return n;
 }
+#if !FEATURE_HAS_FLAG(DEBUG_IGNORE_SPLASH)
 static void print_compiled_features()
 {
 #define _X "\t%s\n"
@@ -176,15 +178,22 @@ static void print_compiled_features()
 #undef X
 #undef _X
 }
+#endif
 static void print_debug_info(int argc, char* const* argv, char* const* envp)
 {
+#ifndef RELEASE
 	fprintf(stderr, "[DEBUG BUILD]\n");
+#else
+	fprintf(stderr, "[RELEASE BUILD]\n");
+#endif
+
 #if ! FEATURE_HAS_FLAG(DEBUG_IGNORE_SPLASH)
 	fprintf(stderr,  _PROJECT " v" _VERSION ": " _DESCRIPTION "\n");
-	fprintf(stderr, " :: written by " _AUTHOR " with <3 (License " _LICENSE ")\n---\n");
+	fprintf(stderr, " :: written by " _AUTHOR " with <3 (License " _LICENSE ")\n");
-#endif
+	fprintf(stderr, "Built with features:\n");
-	fprintf(stderr, "> features:\n");
 	print_compiled_features();
+	fprintf(stderr, "---\n");
+#endif
 
 	fprintf(stderr, "> program: %s (path lookup: "
 #if FEATURE_HAS_FLAG(NO_SEARCH_PATH)