1337349 - Make --enable-fuzzing the default for ASan builds

Status: NEW

(Firefox Build System :: General, defect)

Description

[Christian Holler (:decoder)]

Turning on --enable-fuzzing for our ASan builds will enable code and prefs that are helpful for fuzzing. Since ASan builds are test builds, making them fuzzable by default is a good idea.

Because --enable-fuzzing also enables libfuzzer code by default, there are two concerns here:

1) Code has to be built with -fsanitize-coverage=edge which is a potential slowdown.

2) libfuzzer has several dependencies on newer glibc (3.4.19). This will break compatibility with Ubuntu 12.04 LTS.


To address 1) I will make a try push and see how much slower code and tests actually are. If this doesn't have a huge impact, then I think it's worth adding the flag, also because other fuzzing can also make potential use of ASan coverage.

For 2) glandium suggests to just drop --enable-stdcxx-compat. I was wondering if it is better to bump the allowed GLIBC version to 3.4.19 for ASan builds because build/unix/stdc++compat/stdc++compat.cpp seems to have code that ensures compatibility with 3.4.20/21 and we would lose that as well if we turn off the flag entirely.

glandium, can you confirm my analysis of 2) ?

Comment 1

[Mike Hommey [:glandium]]

Makes sense.