736227 - "ASSERTION: unexpected state" with MathML, astral font name

Status: RESOLVED FIXED

(Core :: MathML, defect)

Description

[Jesse Ruderman]

Attachment: testcase

###!!! ASSERTION: unexpected state: 'aRenderingContext.FontMetrics()->Font(). Equals(aFontMetrics->Font())', file layout/mathml/nsMathMLFrame.cpp, line 338

Comment 1

[Jesse Ruderman]

Attachment: stack trace

Comment 2

[Karl Tomlinson (:karlt)]

I haven't managed to reproduce on Linux x86_64.

The stack doesn't seem to quite line up with the assertion.  If the stack is off by one frame and one line, then that would locate the GetAxisHeight call here:
http://hg.mozilla.org/mozilla-central/annotate/f6d38b80417c/layout/mathml/nsMathMLmfencedFrame.cpp#l255

Given the rendContext->SetFont(fm) immediately prior, I would expect rendContext->FontMetrics() to return fm.

I don't see any obvious problem with nsFont::Equals.

Comment 3

[Jesse Ruderman]

I can reproduce on Linux x86_64, even with an empty profile.

Comment 4

[Jesse Ruderman]

Attachment: stack trace from linux

Is this more helpful?

Comment 5

[Karl Tomlinson (:karlt)]

That trace confirms the GetAxisHeight call in comment 2, thanks.
I can reproduce now.  Seems that this is regression since 7e158ac25de3.
Will narrow down further.

Comment 6

[Karl Tomlinson (:karlt)]

Regression from http://hg.mozilla.org/mozilla-central/rev/edc0871b4e5b

Comment 7

[Alex Keybl [:akeybl]]

Other than this being a regression, what's the justification for tracking this bug? Will this be a common error for MathML users? In what state is the user left when they run into this?

Comment 8

[Karl Tomlinson (:karlt)]

The bug doesn't affect this MathML testcase adversely (from a user perspective).

What the assertion is highlighting is that, for string |a|, a.Equals(a) is false (perhaps only for a certain comparator), which is likely to have wider ranging affects.  Perhaps the problem is only for non-BMP characters, but a problem with surrogates may be a problem with array index counting.

Comment 9

[Jonathan Kew [:jfkthame]]

Attachment: patch, fix surrogate handling during string compare

Argh - silly typo!

Comment 10

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/d19b20df7e70

Comment 11

[Jesse Ruderman]

It's kinda scary that it took an obscure feature (fonts in MathML) to uncover a unicharutil bug. How can that be remedied?

Comment 12

[(no longer active)]

http://hg.mozilla.org/mozilla-central/rev/d19b20df7e70