[pacman-dev] [PATCH] makepkg: optionally attach minimal debuginfo to binaries

[Levente Polyak]

==> 0x00: Summary

I think this looks kind of useful, minidebug enabled binaries could help
debugging and understanding certain type of crashes without the need of
rebuilding and install full debug symbols.

Overall the size increase seems to be round about 3% per binary and
slightly higher per tarball (mainly depending on the amount of binaries
it contains).

The mplayer testcase had some strange effects that may need some deeper
investigation before considering to make this a default option.

Binaries with minidebug option and a corresponding .gnu_debugdata
section do not seem to affect reproducibility.


==> 0x01: Patch adjustments

There are some small adjustments required to this patch, I would
recommend the following changes:

1) scripts/libmakepkg/tidy/strip.sh.in

The new minidebug option is required to be added to the
packaging_options array to make it available in the PKGBUILD's options
array:

    packaging_options+=('strip' 'debug' 'minidebug')


2) etc/makepkg.conf.in

The new option should to be added to the OPTIONS array in the
configuration file. Its default value should also to be added in the
comment above that option, including a description text between both.


==> 0x02: Backtrace example

Following backtrace example was taken from zsh with default and
minidebug options.

(gdb) bt
 #0 0x00007ffff71a0150 in __read_nocancel () from /usr/lib/libc.so.6
 #1 0x000000000041c3a7 in bin_read ()
 #2 0x000000000041d926 in execbuiltin ()
 #3 0x000000000042b59a in ?? ()
 #4 0x000000000042bf4e in ?? ()
 #5 0x000000000042c311 in ?? ()
 #6 0x000000000042db6c in execlist ()
 #7 0x000000000045168b in execif ()
 #8 0x000000000042a581 in ?? ()
 #9 0x000000000042bf4e in ?? ()
#10 0x000000000042c311 in ?? ()

(gdb) bt
 #0 0x00007ffff71a0150 in __read_nocancel () from /usr/lib/libc.so.6
 #1 0x000000000041c3a7 in bin_read ()
 #2 0x000000000041d926 in execbuiltin ()
 #3 0x000000000042b59a in execcmd ()
 #4 0x000000000042bf4e in execpline2 ()
 #5 0x000000000042c311 in execpline ()
 #6 0x000000000042db6c in execlist ()
 #7 0x000000000045168b in execif ()
 #8 0x000000000042a581 in execcmd ()
 #9 0x000000000042bf4e in execpline2 ()
#10 0x000000000042c311 in execpline ()


==> 0x03: File size influence

The file size list below roughly matches the expected size increase and
ends up with around 3% bigger binaries. The percentage size increase per
package is obviously higher compared to a single binaries because the
debug sections are already compress.


1) package -> util-linux    8.70%
   1.7M 1738096
   1.9M 1889416

   binary -> hexdump        3.71%
    47K   47968
    49K   49752

   binary -> lsblk          3.26%
    76K   77296
    78K   79816

   binary -> fdisk          2.74%
   108K  109640
   110K  112640


2) package -> bash          1.14%
   1.3M 1271836
   1.3M 1286376

   binary -> bash           1.86%
   773K  791320
   788K  806080

3) package -> ncmpcpp      13.75%
   610K  624140
   694K  710592

   binary -> ncmpcpp        3.41%
   2.4M 2447816
   2.5M 2531440


4) package -> zsh           2.81%
   1.8M 1883400
   1.9M 1936428

   binary -> zsh            1.47%
   758K  775592
   769K  786968


5) package -> wireshark-gtk 4.49%
   641K  655976
   670K  685452

   binary -> wireshark-gtk  1.48%
   2.0M 2068552
   2.1M 2099256


6) package -> wireshark-qt  3.25%
   2.9M 2983856
   3.0M 3080928

   binary -> wireshark      1.52%
   6.1M 6375200
   6.2M 6472216


==> 0x04: Strange observations

Besides the package firefox, where the minidebug option had no effect at
all, there was some strange effect while testing the mplayer package.

The mplayer and memcoder binaries significantly increase in size while
having missing .gnu_debugdata sections. As there may be more cases
affected by this issue, it should maybe be investigated before
considering to enable this by default.

1) mplayer         26.95%
   17M  17333304
   21M  22005264

2) mencoder        25.96%
   16M  16105880
   20M  20286256


cheers,
Levente

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