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From Rich Felker:
By default, modern GCC generates DWARF2 debug/unwind tables in the
.eh_frame section of the object files/binaries. This adds significant
bloat (as much as 15%) to the size of the busybox binary, including
the portion mapped/loaded into memory at runtime (possibly a big issue
for NOMMU targets), and the section is not strippable with the strip
command due to being part of the loaded program text.
I've since done some further checking - both testing and asking the
GCC developers about it - and it seems the solution is to add to the
CFLAGS -fno-unwind-tables and -fno-asynchronous-unwind-tables. If
debugging is disabled, this will prevent GCC from outputting DWARF2
tables entirely. But since busybox builds with -g by default, the
interesting case is what happens then. I originally thought these
options would break debugging, but they don't; instead, they tell GCC
to output the DWARF2 tables in the .debug_frame section instead of
the newish .eh_frame section (used for exception handling). With these
options added, busybox_unstripped is still fully debuggable, and the
final busybox binary loses the 15% bloat factor from the DWARF2
tables.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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We pass strings to printf directly a lot. Some distros enable some flags
in their gcc by default like -Wformat-security. With these two things, we
end up with a lot of build warnings like so:
loginutils/chpasswd.c:42:3: warning: format not a string literal and
no format arguments [-Wformat-security]
But we don't care. Our focus is first and foremost on size, so adding a
lot of dummy calls like:
- printf(some_constant_string);
+ printf("%s", some_constant_string);
is pointless bloat.
Disable this warning flag if the compiler supports it.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Rob Walker <rwalker@rwalker.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Tristan Schmelcher <tristan_schmelcher@alumni.uwaterloo.ca>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Recent versions of GCC for PowerPC systems suffer from some compiler
bugs which prevent the use of "--enable-target-optspace" in their
configuration, which makes the compiler option "-Os" unavailable;
for reference see
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43810
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48278
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45053
In the result, BusyBox will be compiled without any optimization
options, which causes a huge binary (1.8 MiB for default configuration
on PPC, built with gcc 54.51 from the Yocto / Poky / OpenEmbedded tool
chains). This commit changes behaviour so "-O2" gets used as fallback
when "-Os" is not available. This reduces the image size in above
test to 1.3 MiB. This is still 10...15% more then what we get with
"-Os", but much better than using no optimization at all.
Signed-off-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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Signed-off-by: Dan Fandrich <dan@coneharvesters.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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can use either form
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This is the result after converting mtd-utils' flash_eraseall to BB.
The functionality given by this patch almost the same except that this
one does not support long options.
I needed this tool a system which does not have a lot of flash for RFS
and merging this into BB as the only way out.
[bigeasy@]$ ./scripts/bloat-o-meter bb_wo_fl bb_w_fl
function old new delta
flash_eraseall_main - 1072 +1072
show_progress - 62 +62
packed_usage 25156 25176 +20
applet_names 1958 1973 +15
applet_main 2352 2360 +8
target_endian - 4 +4
applet_nameofs 588 590 +2
applet_install_loc 147 148 +1
------------------------------------------------------------------------------
(add/remove: 3/0 grow/shrink: 5/0 up/down: 1184/0) Total: 1184 bytes
[bigeasy@]$ size miscutils/flash_eraseall.o
text data bss dec hex filename
1586 4 0 1590 636 miscutils/flash_eraseall.o
Signed-off-by: Benedigt Spranger <b.spranger@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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This helps with remembering additional flags like e.g. cpu settings for
people who did not configured their compiler to produce code for their cpu
per default.
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Document in comments that it generally should be thers,
not in LDFLAGS
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function old new delta
procps_scan 1265 1298 +33
aliascmd 278 283 +5
parse_file_cmd 116 120 +4
dname_enc 373 377 +4
setcmd 90 93 +3
execcmd 57 60 +3
count_lines 72 74 +2
process_command_subs 340 339 -1
test_main 409 407 -2
mknod_main 179 177 -2
handle_incoming_and_exit 2653 2651 -2
argstr 1312 1310 -2
shiftcmd 131 128 -3
exitcmd 46 43 -3
dotcmd 297 294 -3
breakcmd 86 83 -3
evalpipe 353 349 -4
evalcommand 1180 1176 -4
evalcmd 109 105 -4
send_tree 374 369 -5
mkfifo_main 82 77 -5
evalsubshell 152 147 -5
typecmd 75 69 -6
letcmd 61 55 -6
add_cmd 1190 1183 -7
main 891 883 -8
ash_main 1415 1407 -8
parse_stream 1377 1367 -10
alloc_procps_scan 55 - -55
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 7/21 up/down: 54/-148) Total: -94 bytes
text data bss dec hex filename
797195 658 7428 805281 c49a1 busybox_old
797101 658 7428 805187 c4943 busybox_unstripped
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appletli.c: add vda's (C)
top: fixlet for incorrect display of "0"
Makefile: reduce stack size from 20k to 16k
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EXTERNALLY_VISIBLE. 5% size reduction of libbusybox.so
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specified libs, and if it succeeds, we try to remove them
one-by-one. If link succeeds, then library is thrown out.
Should solve the problem with SELinux linking in libsepol
even when not needed.
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are currently seen, let's strive to fixup these:
- warn a little bit about unused results
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(8k of shell line edit buffer is an overkill)
# make ARCH=i386 bloatcheck
function old new delta
read_line_input 3933 3967 +34
ifaddrlist 348 345 -3
do_loadfont 208 191 -17
edit_file 840 819 -21
.rodata 129112 129080 -32
uncompress 1305 1268 -37
loadfont_main 566 495 -71
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/6 up/down: 34/-181) Total: -147 bytes
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the final link, the objects/libraries are in the correct order
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nested functions)
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- simplify the cmd_busybox__ a bit and pass the LDFLAGS via -Wl down to CC
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