Symbols blow up binary size to an unreasonable degree on x86_64-unknown-linux-gnu

[crumblingstatue]

Standard hello world program generated with cargo new --bin mytest

fn main() {
    println!("Hello, world!");
}

Built with cargo build --release, the resulting binary size is 4270408 bytes.
This sounds unreasonably large for a hello world program.

After strip --strip-all, we get 449224.

The non-stripped version is almost 10 times larger than the stripped version. Why?

This is with rustc 1.23.0-nightly (fa26421f5 2017-11-15), installed through rustup.

$ rustc -vV
rustc 1.23.0-nightly (fa26421f5 2017-11-15)
binary: rustc
commit-hash: fa26421f56e385b1055e65b29a55b36bb2eae23e
commit-date: 2017-11-15
host: x86_64-unknown-linux-gnu
release: 1.23.0-nightly
LLVM version: 4.0

Here is stable rustc 1.21.0 (3b72af97e 2017-10-09) for good measure:
Normal: 4059968
Stripped: 404096

This time, the initial size is lower, but the stripped size is even smaller, making the non-stripped version slightly more than 10 times larger.

(As a sidenote, I've been noticing that binary sizes for the same program have been steadily increasing with every new rustc, at least on x86_64-unknown-linux-gnu, but that's a separate issue, I suppose)

[kennytm]

On x86_64-apple-darwin:

Version	Size	After strip -x
1.23.0-nightly (fa26421f5 2017-11-15)	525348	377348
1.23.0-nightly (ff0f5de3b 2017-11-14)	525348	(not checked)
1.22.0-beta.3 (cc6ed0640 2017-11-13)	520164	373140
1.21.0 (3b72af97e 2017-10-09)	452684	310548
1.15.1 (021bd294c 2017-02-08)	390608	268696
1.14.0 (e8a012324 2016-12-16)	408304	285392
1.13.0 (021bd294c 2017-02-08)	348872	277232

The size is definitely growing but not something that increases by 10×.

---

On x86_64-pc-windows-msvc:

Version	Size
1.23.0-nightly (fa26421f5 2017-11-15)	134144
1.21.0 (3b72af97e 2017-10-09)	130048

Probably a Linux-only problem.

[crumblingstatue]

@kennytm updated OP with rustc -vV info.

[kennytm]

Repro'd on Linux with stable. (Not sure about the BSDs)

Version	Size	After strip
1.21.0 (3b72af97e 2017-10-09)	4062904	404184
1.15.1 (021bd294c 2017-02-08)	3465968	(not checked)
1.14.0 (e8a012324 2016-12-16)	2068056	372256
1.13.0 (2c6933acc 2016-11-07)	647864	364064
1.12.0 (cfcb716cf 2016-07-03)	652216	(not checked)
1.10.0 (cfcb716cf 2016-07-03)	647760	(not checked)
1.5.0 (3d7cd77e4 2015-12-04)	557208	(not checked)
1.0.0 (a59de37e9 2015-05-13)	579688	(not checked)

The initial blow up problem comes from 1.14.0.

---

Comparing the readelf -S output of 1.13.0 and 1.14.0, we find that 1.14.0 has 3 more sections, .debug_pubnames, .debug_macinfo and .debug_pubtypes. The existing debug info sections are also much larger.

readelf -S -W 1.13.0

$ readelf -S -W 1.13.0
There are 42 section headers, starting at offset 0x9d838:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
  [ 1] .interp           PROGBITS        0000000000000270 000270 00001c 00   A  0   0  1
  [ 2] .note.ABI-tag     NOTE            000000000000028c 00028c 000020 00   A  0   0  4
  [ 3] .note.gnu.build-id NOTE            00000000000002ac 0002ac 000024 00   A  0   0  4
  [ 4] .gnu.hash         GNU_HASH        00000000000002d0 0002d0 0000b4 00   A  5   0  8
  [ 5] .dynsym           DYNSYM          0000000000000388 000388 0009c0 18   A  6   3  8
  [ 6] .dynstr           STRTAB          0000000000000d48 000d48 00065a 00   A  0   0  1
  [ 7] .gnu.version      VERSYM          00000000000013a2 0013a2 0000d0 02   A  5   0  2
  [ 8] .gnu.version_r    VERNEED         0000000000001478 001478 000110 00   A  6   4  8
  [ 9] .rela.dyn         RELA            0000000000001588 001588 003558 18   A  5   0  8
  [10] .rela.plt         RELA            0000000000004ae0 004ae0 000768 18  AI  5  27  8
  [11] .init             PROGBITS        0000000000005248 005248 00001a 00  AX  0   0  4
  [12] .plt              PROGBITS        0000000000005270 005270 000500 10  AX  0   0 16
  [13] .plt.got          PROGBITS        0000000000005770 005770 000018 00  AX  0   0  8
  [14] .text             PROGBITS        0000000000005790 005790 03fc69 00  AX  0   0 16
  [15] .fini             PROGBITS        00000000000453fc 0453fc 000009 00  AX  0   0  4
  [16] .rodata           PROGBITS        0000000000045440 045440 005031 00   A  0   0 64
  [17] .eh_frame_hdr     PROGBITS        000000000004a474 04a474 00148c 00   A  0   0  4
  [18] .eh_frame         PROGBITS        000000000004b900 04b900 006254 00   A  0   0  8
  [19] .gcc_except_table PROGBITS        0000000000051b54 051b54 002578 00   A  0   0  4
  [20] .tdata            PROGBITS        0000000000254d90 054d90 0000f0 00 WAT  0   0 16
  [21] .init_array       INIT_ARRAY      0000000000254e80 054e80 000010 00  WA  0   0  8
  [22] .fini_array       FINI_ARRAY      0000000000254e90 054e90 000008 00  WA  0   0  8
  [23] .jcr              PROGBITS        0000000000254e98 054e98 000008 00  WA  0   0  8
  [24] .data.rel.ro      PROGBITS        0000000000254ea0 054ea0 002ee8 00  WA  0   0 32
  [25] .dynamic          DYNAMIC         0000000000257d88 057d88 000220 10  WA  6   0  8
  [26] .got              PROGBITS        0000000000257fa8 057fa8 000040 08  WA  0   0  8
  [27] .got.plt          PROGBITS        0000000000258000 058000 000290 08  WA  0   0  8
  [28] .data             PROGBITS        00000000002582a0 0582a0 0001e1 00  WA  0   0 32
  [29] .bss              NOBITS          00000000002584a0 058481 000fd8 00  WA  0   0 32
  [30] .comment          PROGBITS        0000000000000000 058481 000079 01  MS  0   0  1
  [31] .debug_aranges    PROGBITS        0000000000000000 0584fa 0023a0 00      0   0  1
  [32] .debug_info       PROGBITS        0000000000000000 05a89a 00b63f 00      0   0  1
  [33] .debug_abbrev     PROGBITS        0000000000000000 065ed9 00186a 00      0   0  1
  [34] .debug_line       PROGBITS        0000000000000000 067743 002b12 00      0   0  1
  [35] .debug_frame      PROGBITS        0000000000000000 06a258 006a60 00      0   0  8
  [36] .debug_str        PROGBITS        0000000000000000 070cb8 007aee 01  MS  0   0  1
  [37] .debug_loc        PROGBITS        0000000000000000 0787a6 010c95 00      0   0  1
  [38] .debug_ranges     PROGBITS        0000000000000000 08943b 002220 00      0   0  1
  [39] .shstrtab         STRTAB          0000000000000000 09d69d 000198 00      0   0  1
  [40] .symtab           SYMTAB          0000000000000000 08b660 008a30 18     41 1199  8
  [41] .strtab           STRTAB          0000000000000000 094090 00960d 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

readelf -S -W 1.14.0

$ readelf -S -W 1.14.0
There are 45 section headers, starting at offset 0x1f8318:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
  [ 1] .interp           PROGBITS        0000000000000270 000270 00001c 00   A  0   0  1
  [ 2] .note.ABI-tag     NOTE            000000000000028c 00028c 000020 00   A  0   0  4
  [ 3] .note.gnu.build-id NOTE            00000000000002ac 0002ac 000024 00   A  0   0  4
  [ 4] .gnu.hash         GNU_HASH        00000000000002d0 0002d0 0000b4 00   A  5   0  8
  [ 5] .dynsym           DYNSYM          0000000000000388 000388 0009c0 18   A  6   3  8
  [ 6] .dynstr           STRTAB          0000000000000d48 000d48 00065a 00   A  0   0  1
  [ 7] .gnu.version      VERSYM          00000000000013a2 0013a2 0000d0 02   A  5   0  2
  [ 8] .gnu.version_r    VERNEED         0000000000001478 001478 000110 00   A  6   4  8
  [ 9] .rela.dyn         RELA            0000000000001588 001588 0035a0 18   A  5   0  8
  [10] .rela.plt         RELA            0000000000004b28 004b28 000768 18  AI  5  27  8
  [11] .init             PROGBITS        0000000000005290 005290 00001a 00  AX  0   0  4
  [12] .plt              PROGBITS        00000000000052b0 0052b0 000500 10  AX  0   0 16
  [13] .plt.got          PROGBITS        00000000000057b0 0057b0 000018 00  AX  0   0  8
  [14] .text             PROGBITS        00000000000057d0 0057d0 041f29 00  AX  0   0 16
  [15] .fini             PROGBITS        00000000000476fc 0476fc 000009 00  AX  0   0  4
  [16] .rodata           PROGBITS        0000000000047740 047740 0052b1 00   A  0   0 64
  [17] .eh_frame_hdr     PROGBITS        000000000004c9f4 04c9f4 0014d4 00   A  0   0  4
  [18] .eh_frame         PROGBITS        000000000004dec8 04dec8 00645c 00   A  0   0  8
  [19] .gcc_except_table PROGBITS        0000000000054324 054324 002700 00   A  0   0  4
  [20] .tdata            PROGBITS        0000000000256d50 056d50 0000f0 00 WAT  0   0 16
  [21] .init_array       INIT_ARRAY      0000000000256e40 056e40 000010 00  WA  0   0  8
  [22] .fini_array       FINI_ARRAY      0000000000256e50 056e50 000008 00  WA  0   0  8
  [23] .jcr              PROGBITS        0000000000256e58 056e58 000008 00  WA  0   0  8
  [24] .data.rel.ro      PROGBITS        0000000000256e60 056e60 002f28 00  WA  0   0 32
  [25] .dynamic          DYNAMIC         0000000000259d88 059d88 000220 10  WA  6   0  8
  [26] .got              PROGBITS        0000000000259fa8 059fa8 000040 08  WA  0   0  8
  [27] .got.plt          PROGBITS        000000000025a000 05a000 000290 08  WA  0   0  8
  [28] .data             PROGBITS        000000000025a2a0 05a2a0 0001e1 00  WA  0   0 32
  [29] .bss              NOBITS          000000000025a4a0 05a481 000ff8 00  WA  0   0 32
  [30] .comment          PROGBITS        0000000000000000 05a481 000079 01  MS  0   0  1
  [31] .debug_aranges    PROGBITS        0000000000000000 05a4fa 0023a0 00      0   0  1
  [32] .debug_pubnames   PROGBITS        0000000000000000 05c89a 01a19a 00      0   0  1
  [33] .debug_info       PROGBITS        0000000000000000 076a34 0716cd 00      0   0  1
  [34] .debug_abbrev     PROGBITS        0000000000000000 0e8101 002763 00      0   0  1
  [35] .debug_line       PROGBITS        0000000000000000 0ea864 02c556 00      0   0  1
  [36] .debug_frame      PROGBITS        0000000000000000 116dc0 006a60 00      0   0  8
  [37] .debug_str        PROGBITS        0000000000000000 11d820 056459 01  MS  0   0  1
  [38] .debug_loc        PROGBITS        0000000000000000 173c79 010c95 00      0   0  1
  [39] .debug_macinfo    PROGBITS        0000000000000000 18490e 000008 00      0   0  1
  [40] .debug_pubtypes   PROGBITS        0000000000000000 184916 00ab8a 00      0   0  1
  [41] .debug_ranges     PROGBITS        0000000000000000 18f4a0 0567a0 00      0   0  1
  [42] .shstrtab         STRTAB          0000000000000000 1f814c 0001c7 00      0   0  1
  [43] .symtab           SYMTAB          0000000000000000 1e5c40 008da8 18     44 1238  8
  [44] .strtab           STRTAB          0000000000000000 1ee9e8 009764 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

Detailed breakdown of size delta for each section

Section	1.13 size	1.14 size	Δ
.interp	28	28	-
.note.ABI-tag	32	32	-
.note.gnu.build-id	36	36	-
.gnu.hash	180	180	-
.dynsym	2496	2496	-
.dynstr	1626	1626	-
.gnu.version	208	208	-
.gnu.version_r	272	272	-
.rela.dyn	13656	13728	+0.53%
.rela.plt	1896	1896	-
.init	26	26	-
.plt	1280	1280	-
.plt.got	24	24	-
.text	261225	270121	+3.41%
.fini	9	9	-
.rodata	20529	21169	+3.12%
.eh_frame_hdr	5260	5332	+1.37%
.eh_frame	25172	25692	+2.07%
.gcc_except_table	9592	9984	+4.09%
.tdata	240	240	-
.init_array	16	16	-
.fini_array	8	8	-
.jcr	8	8
.data.rel.ro	12008	12072	+0.53%
.dynamic	544	544	-
.got	64	64	-
.got.plt	656	656	-
.data	16	16	-
.bss	4056	4088	+0.79%
.comment	121	121	-
.debug_aranges	9120	9120	-
.debug_pubnames	-	106906	new
.debug_info	46655	464589	+895.80%
.debug_abbrev	6250	10083	+61.33%
.debug_line	11026	181590	+1546.95%
.debug_frame	27232	27232	-
.debug_str	31470	355369	+1022.88%
.debug_loc	68757	68757	-
.debug_macinfo	8	8	new
.debug_pubtypes	-	43914	new
.debug_ranges	8736	354208	+3954.58%
.shstrtab	408	455	+11.52%
.symtab	35376	36264	+2.51%
.strtab	38413	38756	+0.89%

[kennytm]

#43392 seems to be the same problem. Since Windows and macOS places the debug symbols externally (*.pdb and *.dSYM respectively), we don't see the size blow up on those platforms.

[est31]

This seems like a very important thing. Size affects linkage time, affects compilation speed.

[kennytm]

From the 1.14.0 release note I believe the cause of the 1.13.0 → 1.14.0 jump is introduced by #37280, where libstd starts to be built with -C debuginfo=1. However the underlying cause is still #43392, that release builds copy the debuginfo from libstd.

[michaelwoerister]

Making the assumption that this is caused by libstd debuginfo, the size difference in percent should become smaller for larger programs, that is, running strip on a big crate should not reduce its size by 90%. Has anybody tried this?

[Michael-F-Bryan]

On mdbook, a non-trivial sized project with about 5.5 kloc of Rust.

$ rustc --version
rustc 1.24.0-nightly (687d3d15b 2018-01-02)
$ cargo build --release
$ du -h ./target/release/mdbook
12M	./target/release/mdbook
$ strip ./target/release/mdbook 
$ du -h ./target/release/mdbook
6.3M	./target/release/mdbook

So stripping debug info goes from 12M to 6.3M.

[whitequark]

The C/C++ toolchain (whether GCC or Clang) on Linux solves this with -gsplit-dwarf, which results in similar products as the *.pdb or *.dSYM on Windows and macOS; to anyone interested in implementing the support, it would be as simple as setting the appropriate LLVM codegen option (as seen in clang):

llvm::TargetOptions &Options;
// ...
if (CodeGenOpts.EnableSplitDwarf)
  Options.MCOptions.SplitDwarfFile = CodeGenOpts.SplitDwarfFile;

[kennytm]

Oh interesting. cc @main-- rust-lang/rfcs#2154.