108950 - Unaligned memory access in nsCompressedCharMap::SetChars

Status: RESOLVED DUPLICATE of bug 102113

(Core :: Layout, defect)

Description

[bobbell]

nsCompressedCharMap::SetChars accesses unaligned memory.  With the default
settings on Tru64 UNIX, Tru64 UNIX correctly detects this, corrects it, and
prints a warning message.  However, Tru64 UNIX can also be set to crash with
this behavior, and it is technically incorrect.

The problem was discovered using a recent nightly build.  Lines 298 and 299 of
nsCompressedCharMap.cpp are at fault.  They read:
    NS_ASSERTION(page[i]==0, "this page should be unused");
    page[i] = aPage[i];

page (from my crash dump) is a pointer on a four byte boundary.  This is because
is an offset into mCCMap, which is an array of 16-bit data types.  However, page
is a point to ALU_TYPE, which on Tru64 UNIX is a 64-bit data type.  Thus, page
is not properly aligned.

Comment 1

[kill this account]

This is a dup of bug 102133 (although the info is new so I will copy it over
to bug 102133).

Brendan indicates he knows a fix.


*** This bug has been marked as a duplicate of 102133 ***

Comment 2

[[e-mail]]

You've dupped the wrong bug...

Comment 3

[bobbell]

This bug should have been marked as a duplicate of bug 102113, not bug 102133.  
I am correcting that.  The information was copied over to the correct bug, 
though.

*** This bug has been marked as a duplicate of 102113 ***

Comment 4

[kill this account]

thanks