https://llvm.org/bugs/show_bug.cgi?id=26842
Bug ID: 26842
Summary: LLDB GUI segfault when continuing with the thread
frame list expanded
Product: lldb
Version: 3.8
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: lldb-dev@lists.llvm.org
Reporter: kknb1...@gmail.com
CC: llvm-b...@lists.llvm.org
Classification: Unclassified
Created attachment 15986
--> https://llvm.org/bugs/attachment.cgi?id=15986&action=edit
Example backtrace of a crash, plus the proposed patch to fix
I have a fix for this, but I wasn't sure if the correct etiquette is to file a
bug report before posting a patch to lldb-commits?
If the frame stack changes while the list is expanded in the Threads window,
there will be a high likelihood of a segfault. For example, expanding the list
and then "continue" to another breakpoint where the list is different. I can
give a specific program and instructions if required but any program should do
it. An example stack trace is attached.
This is with the version of lldb shipped with XCode 7.2.1 (lldb-340.4.119.1) as
well as the current head (as at 04/Mar/16).
The problem is that, when creating the updated list it is done with
vector<TreeItem>::resize( <new size>, <new value> );
(via calls to TreeItem::Resize in IOHandler.cpp lines 3312 and 3422). The
intention of the code is to fill the m_children vector with copies of <new
value>, but std::vector::resize only uses the <new value> for new values -
items already in the vector are left untouched. Hence all items up to the old
size will have invalid pointers to parent etcetera, and subsequent Draw calls
will screw up.
I propose to insert a call to TreeItem::ClearChildren() immediately before the
TreeItem::Resize(..) calls so that all children correctly take on the new
value.
A patch is attached, but I could only append one file so it's after the
backtrace.
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