Bug 41500: Optimize for size on Android.

Merge Info

Issues

Resolves

• #41500 (closed)
• tor-browser#xxxxx
• mullvad-browser#xxxxx

Related

• tor-browser-build#xxxxx
• tor-browser#xxxxx
• mullvad-browser#xxxxx

Merging

Target Branches

• main: esr140-15.0
• maint-14.5: esr128-14.5
• maint-13.5: esr115-13.5

Backporting

Timeline

• No Backport (preferred): patchset for the next major stable
• Immediate: patchset needed as soon as possible
• Next Minor Stable Release: patchset that needs to be verified in nightly before backport
• Eventually: patchset that needs to be verified in alpha before backport

(Optional) Justification

• Emergency security update: patchset fixes CVEs, 0-days, etc
• Censorship event: patchset enables censorship circumvention
• Critical bug-fix: patchset fixes a bug in core-functionality
• Consistency: patchset which would make development easier if it were in both the alpha and release branches; developer tools, build system changes, etc
• Sponsor required: patchset required for sponsor
• Other: please explain

Issue Tracking

• Link resolved issues with appropriate Release Prep issue for changelog generation

Uplifting

• Patchset is a candidate for uplift to upstream projects (e.g. mingw, clang, etc)

Review

Request Reviewer

• Request review from an applications developer depending on modified system:
  • NOTE: if the MR modifies multiple areas, please /request_review all the relevant reviewers
  • accessibility : henry
  • android : clairehurst, dan
  • build system : boklm
  • extensions : ma1
  • firefox internals (XUL/JS/XPCOM) : jwilde, ma1
  • fonts : pierov
  • frontend (implementation) : henry
  • frontend (review) : donuts, morgan
  • localization : henry, pierov
  • macOS : clairehurst, dan
  • nightly builds : boklm
  • rebases/release-prep : boklm, dan, ma1, morgan, pierov
  • security : jwilde, ma1
  • signing : boklm, morgan
  • updater : pierov
  • windows : jwilde, morgan
  • misc/other : morgan, pierov

Change Description

We're very tight on Android.

With the apks I built so far, we are slightly over the 100MB threshold with x86 apks.

A trivial flag we initially dismissed was to optimize binaries for size (-Os).

So, I added this flag to tor and its dependencies. I also added -ffunction-sections -fdata-sections, which should allow strip to remove more, but I don't think they're actually doing much.

Shall this not be enough, we can also try to remove some OpenSSL functionalities we don't use.

How Tested

I've only built, I haven't tried the binaries because it'd require a full Android build. I will do it at a certain point.

I built, then I extracted libTor.so from the output, and I compressed it:

rbm/rbm build tor --target alpha --target torbrowser-android-x86
tar -xf out/tor/tor-...-android-x86-....tar.zst
7z a -mx=9 .../tor.zip .../libTor.so

I compared the zip size before and after the change:

-rw-rw-r-- 1 piero piero 4071500 24 giu 09.30 tor-before.zip
-rw-rw-r-- 1 piero piero 3789643 24 giu 10.33 tor-after.zip

So, it's less than 300kB, but it should be good to allow us to release (hopefully).

At this point, even this small improvement is helpful.

I've also verified -Os is actually working on projects, by checking the tarballs' size before and after the changes.

-rw-r--r-- 1 piero piero  278565 24 giu 09.57 libevent-2.1.12-android-x86-cc81c2.tar.zst
-rw-r--r-- 1 piero piero  627229 12 giu 17.07 libevent-2.1.12-android-x86-800187.tar.zst

-rw-r--r-- 1 piero piero 11091939 24 giu 09.57 openssl-3.5.0-android-x86-b59be7.tar.zst
-rw-r--r-- 1 piero piero 11336141 12 giu 17.05 openssl-3.5.0-android-x86-42a0e8.tar.zst

-rw-r--r-- 1 piero piero  86084 24 giu 09.58 zlib-1.3.1-android-x86-12cf9d.tar.zst
-rw-r--r-- 1 piero piero  91862 12 giu 17.08 zlib-1.3.1-android-x86-1c3c17.tar.zst

-rw-r--r-- 1 piero piero 424881 24 giu 10.11 zstd-1.5.7-android-x86-795f14.tar.zst
-rw-r--r-- 1 piero piero 480363 12 giu 17.09 zstd-1.5.7-android-x86-01ef7e.tar.zst