[lldb-dev] Problem with ClangExpressionDeclMap

Zachary Turner zturner at google.com
Mon Jan 12 11:50:57 PST 2015

Was looking into this bug <http://llvm.org/bugs/show_bug.cgi?id=22177> on
Windows, and I traced it down to an issue in ClangExpressionDeclMap.
ClangExpressionDeclMap::FindExternalVisibleDecls has a piece of code that
looks like this:

            if (namespace_decl && module_sp)
                const bool include_symbols = false;

            else if (target && !namespace_decl)
                const bool include_symbols = true;

                // TODO Fix FindFunctions so that it doesn't return
                //   instance methods for eFunctionNameTypeBase.


So it's only searching for the base name if the function is in a namespace,
and if it's at global scope it's searching for the full name.

I'm not sure why this works on other platforms, but on Windows it doesn't
work because if I have this code:

int foo(int x)

then the full name of this function is ?foo@@YAHH at Z

If I change eFunctionNameTypeFull to eFunctionNameTypeBase then everything
works, and "p foo" finds the function.  So I've got a couple of questions:

1) Why all this complicated logic?  I would expect that if I type "p foo"
then it would just print everything whose base name is foo and is visible
from within the current scope?  Am I underthinking this?  There's special
cases for namespaces, global scope, instance methods, variables, functions,
and it looks for things in certain orders, etc.  Is there any reason why it
can't just find everything with a basename of foo visible within the
current stack frame?

2) I'm not sure what this comment means:
                // TODO Fix FindFunctions so that it doesn't return
                //   instance methods for eFunctionNameTypeBase.
I changed it to eFunctionNameTypeBase and it fixes the original bug on
Windows.  I inserted a class with an instance method named foo() and also a
global method named foo(), and running "p foo" doesn't find the instance
method, only the global method.  Is it possible this was somehow fixed, and
it was forgotten to change this back to eFunctionNameTypeBase?

3) Why does this work on other platforms?  full names are mangled on other
platforms too, so I don't know how "p foo" doesn't run into this same issue
on other platforms.  Any ideas?

Currently the best fix I have for this bug on Windows is to change
eFunctionNameTypeFull to eFunctionNameTypeBase.  but I want to get some
thoughts on that worrisome comment before I go forward with that patch.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20150112/f61ca45e/attachment.html>

More information about the lldb-dev mailing list