479057 - Prefixing a string to an empty autostring causes an extra pointless copy

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[[e-mail]]

Steps to reproduce problem:
1. Start a debug build
2. Turn off keyword.enabled
3. Try to load ://
Actual result: ###!!! ASSERTION: buffer incorrectly sized: 'a.Length() == headLen', file nsTSubstringTuple.cpp, line 78

What's happening here is that nsDefaultURIFixup strips off the bogus :// and attempts to prefix http:// in its place. It does this using

uriString.Assign(NS_LITERAL_CSTRING("http://") + uriString);

We create a substring tuple from "http://" and [R]uriString, and decide that [L]uriString doesn't depend on it, so that we can write to it in place. So we adjust [L]uriString's length, and then try to copy [R]uriString and "http://". Of course since [L]uriString and [R]uriString are the same thing, we've just changed [R]uriString's length which is why we get confused as to what to copy.

Comment 1

[[e-mail]]

We actually copy "http://" to uriString, and then uriString to uriString.

Comment 2

[[e-mail]]

Attachment: Somewhat contrived test case

This test fails with our current code.

Comment 3

[[e-mail]]

Attachment: Confident patch

Passes the test :-)

Comment 4

[[e-mail]]

Pushed changeset 6c0ff682551d to mozilla-central.

Actually I pushed it yesterday. See bug 478732 for the gory details.

Comment 6

[Daniel Veditz [:dveditz]]

would we not want this on the 1.9.2 branch if it's good for the 1.9.1 branch?

Comment 7

[[e-mail]]

It landed before 1.9.2 branched.

Comment 8

[Mike Beltzner [:beltzner, not reading bugmail]]

Comment on attachment 362917 [details] [diff] [review]
Confident patch

a=beltzner for 1.9.1.10

Comment 9

[[e-mail]]

Pushed changeset 9a06693cdbb4 to releases/mozilla-1.9.1