bloat-o-meter: add usage info

Signed-off-by: Bartosz Golaszewski <[email protected]>
Signed-off-by: Denys Vlasenko <[email protected]>

Author: brgl

docs/keep_data_small.txt

@@ -138,13 +138,6 @@ less readable, use #defines:
 #define sector (G.sector)
 
 
-		Word of caution
-
-If applet doesn't use much of global data, converting it to use
-one of above methods is not worth the resulting code obfuscation.
-If you have less than ~300 bytes of global data - don't bother.
-
-
 		Finding non-shared duplicated strings
 
 strings busybox | sort | uniq -c | sort -nr
@@ -224,6 +217,14 @@ Result (non-static busybox built against glibc):
 
 		Keeping code small
 
+Use scripts/bloat-o-meter to check whether introduced changes
+didn't generate unnecessary bloat. This script needs unstripped binaries
+to generate a detailed report. To automate this, just use
+"make bloatcheck". It requires busybox_old binary to be present,
+use "make baseline" to generate it from unmodified source, or
+copy busybox_unstripped to busybox_old before modifying sources
+and rebuilding.
+
 Set CONFIG_EXTRA_CFLAGS="-fno-inline-functions-called-once",
 produce "make bloatcheck", see the biggest auto-inlined functions.
 Now, set CONFIG_EXTRA_CFLAGS back to "", but add NOINLINE

scripts/bloat-o-meter

@@ -7,11 +7,14 @@
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 
-import sys, os#, re
+import sys, os
 
 def usage():
-    sys.stderr.write("usage: %s [-t] file1 file2\n" % sys.argv[0])
-    sys.exit(-1)
+    sys.stderr.write("usage: %s [-t] file1 file2 [-- <readelf options>]\n"
+                        % sys.argv[0])
+    sys.stderr.write("\t-t\tShow time spent on parsing/processing\n")
+    sys.stderr.write("\t--\tPass additional parameters to readelf\n")
+    sys.exit(1)
 
 f1, f2 = (None, None)
 flag_timing, dashes = (False, False)
@@ -31,6 +34,8 @@ for f in sys.argv[1:]:
             f1 = f
         elif f2 is None:
             f2 = f
+        else:
+            usage()
 if flag_timing:
     import time
 if f1 is None or f2 is None: