factor: factor2 variable is unused now, drop it

[oweals/busybox.git] / docs / keep_data_small.txt

diff --git a/docs/keep_data_small.txt b/docs/keep_data_small.txt
index 079bac3a6de7ea99bf16021dd8dfd3718d83c5e8..218d4f2eeb6bbae9019713dfc667f8240bc42c3d 100644 (file)
--- a/docs/keep_data_small.txt
+++ b/docs/keep_data_small.txt
@@ -59,7 +59,7 @@ wait
                Example 1
 
 One example how to reduce global data usage is in
-archival/libunarchive/decompress_unzip.c:
+archival/libarchive/decompress_gunzip.c:
 
 /* This is somewhat complex-looking arrangement, but it allows
  * to place decompressor state either in bss or in
@@ -87,7 +87,7 @@ take a look at archival/gzip.c. Here all global data is replaced by
 single global pointer (ptr_to_globals) to allocated storage.
 
 In order to not duplicate ptr_to_globals in every applet, you can
-reuse single common one. It is defined in libbb/messages.c
+reuse single common one. It is defined in libbb/ptr_to_globals.c
 as struct globals *const ptr_to_globals, but the struct globals is
 NOT defined in libbb.h. You first define your own struct:
 
@@ -103,7 +103,15 @@ smaller code. In order to assign it, use SET_PTR_TO_GLOBALS macro:
 
        SET_PTR_TO_GLOBALS(xzalloc(sizeof(G)));
 
-Typically it is done in <applet>_main().
+Typically it is done in <applet>_main(). Another variation is
+to use stack:
+
+int <applet>_main(...)
+{
+#undef G
+       struct globals G;
+       memset(&G, 0, sizeof(G));
+       SET_PTR_TO_GLOBALS(&G);
 
 Now you can reference "globals" by G.a, G.buf and so on, in any function.
 
@@ -138,11 +146,9 @@ less readable, use #defines:
 #define sector (G.sector)
 
 
-               Word of caution
+               Finding non-shared duplicated strings
 
-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.
+strings busybox | sort | uniq -c | sort -nr
 
 
                gcc's data alignment problem
@@ -219,6 +225,14 @@ 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