Closed Bug 255982 Opened 19 years ago Closed 16 years ago

hang (infinite loop) printing floats over page break where containing box contains no non-float items


(Core :: Layout: Floats, defect)

Not set





(Reporter: ed, Assigned: MatsPalmgren_bugz)



(Keywords: hang, testcase)


(8 files)

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040813 Epiphany/1.3.2
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8a3) Gecko/20040814

Mozilla, Firefox, etc. stall/hang with 99% CPU utilisation on print layout (inc.
print preview) with this page:

<div style="width: 60%; float: left; height: 20cm;">a float</div>
<div style="width: 60%; float: left; height: 20cm;">overlaps page break</div>
<div style="width: 60%; float: left;">3rd float</div>
<div style="width: 60%; float: left;">4th float</div>

This is a minimal testcase for a problem observed at e.g. and others.

I will attach testcases and analysis.

Reproducible: Always
Steps to Reproduce:
1. Load page
2. Select File->Print or File->Print Preview
Actual Results:  
Hang with 99% CPU utilisation

Seen on Linux (mozilla CVS 20040816, mozilla 1.7.2 Gecko/20040813, firefox 0.9.3
Gecko/20040813) and on Windows (firefox 0.9.2 Gecko/20040707)
1. The <!DOCTYPE HTML> is to force Mozilla into standards mode, to demonstrate
that this is not a quirks mode bug.
2. I have only tested this on A4 paper; if you are using a different paper size
you may need to adjust the div heights to ensure that the second div falls
across the page break.
Mozilla+GDB is run from within the build tree with this command (bash):

MOZILLA_FIVE_HOME=dist/bin LD_LIBRARY_PATH=dist/bin:dist/bin/plugins
NSPR_LOG_FILE=foo.log NSPR_LOG_MODULES=printing-layout:4
GECKO_BLOCK_DEBUG_FLAGS=reflow,really-noisy-reflow gdb dist/bin/mozilla-bin

Output when run outside the debugger is identical.

The output from three reflows is given. The breakpoint in between is
nsSimplePageSequence.cpp:440 as the infinite loop is the for loop from
nsSimplePageSequence.cpp:378 to nsSimplePageSequence.cpp:449.
Here a <br /> is inserted in the flow. This prevents the hang and causes the
page to layout correctly.
A small amount of text is inserted into the flow - not enough for a line break.
The hang still occurs.
This is what I believe is happening (just guesswork; someone who understands the
code can confirm/correct this).
The infinite loop in nsSimplePageSequenceFrame::Reflow occurs because when the
extra continuing page is added at
reflow starts from the top of the new page and no content is left on previous pages.
This is because there is one line object that contains all the floats and reflow
views line objects as atomic; thus a line object that is greater in height than
the page height breaks the layout model.
The text with a line break causes the line object to be split; the first line
object is then placed on the first page and the second line object on the second
I've tried to think what the fix would look like but haven't got anywhere yet.
Hopefully someone who understands the line layout model is watching.
Is bug 255748 caused by this as well?
I don't think so; the code paths are different.
Closed: 19 years ago
Keywords: hang
Resolution: --- → FIXED
Reopening the bug, how does this get fixed without a checkin?
Resolution: FIXED → ---
First test case does not fail for me, but the others fail as described

DP alpha 2 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b4)
Gecko/20050715 Firefox/1.0+
Ever confirmed: true
Keywords: testcase
*** Bug 343191 has been marked as a duplicate of this bug. ***
(In reply to comment #14)
> *** Bug 343191 has been marked as a duplicate of this bug. ***

Here's yet another test case to try. This causes a hang on 1.0.7, 1.0.8, and on CentOS and 1.0.7 on Gentoo, but works fine with on Windows.
Blocks: 360224
Flags: blocking1.9?
Flags: blocking1.9? → blocking1.9-
Whiteboard: [wanted-1.9]
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a7pre) Gecko/2007071105 Minefield/3.0a7pre

None of the attached testcases hang for me in yesterday's trunk build. In a build without the patch for 285608, I hang on the "Third" and "Fourth" testcase. This should probably be duped to that bug or resolved as FIXED and marked as dependent.
No longer blocks: 360224
All the testcases and url are worksforme, with current trunk build.
Adam mentioned in comment 16 that this got fixed by the patch for bug 285608, so I'm marking this fixed and make it dependent on that bug.
Closed: 19 years ago16 years ago
Depends on: 285608
Resolution: --- → FIXED
Flags: in-testsuite?
Flags: wanted1.9+
Whiteboard: [wanted-1.9]
Added crashtests:
Flags: in-testsuite? → in-testsuite+
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