Commit Graph

112 Commits

Author SHA1 Message Date
Saleem Abdulrasool bb19a13c0b second pass over removal of Mutex and Condition
llvm-svn: 270024
2016-05-19 05:13:57 +00:00
Ted Woodward 911d57840a Keep original source path and mapped path in LineEntry
Summary:
The "file" variable in a LineEntry was mapped using target.source-map, except when stepping through inlined code. This patch adds a new variable to LineEntry, "original_file", that contains the original file from the debug info. "file" will continue to (possibly) be mapped.

Some code has been changed to use "original_file". This is code dealing with symbols. Code dealing with source files will still use "file". Reviewers, please confirm that these particular changes are correct.

Tests run on Ubuntu 12.04 show no regression.

Reviewers: clayborg, jingham

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D20135

llvm-svn: 269250
2016-05-11 22:46:53 +00:00
Jim Ingham cef461772e When building the list of variables we're going to write "using $_lldb_local_vars"
statements for, be sure not to include variables that have no locations.  We wouldn't
be able to realize them, and that will cause all expressions to fail.

llvm-svn: 267500
2016-04-26 00:29:59 +00:00
Greg Clayton a32532bfa5 Fix StackFrame::GetVariables(...) function that was broken by 261858 when lambda functions were added to Block::AppendBlockVariables(). The Stackframe::GetVariables(...) function should get all variables regardless if they are in scope.
This wasn't caught by the test suite so I added a test for it.

llvm-svn: 267478
2016-04-25 21:54:10 +00:00
Enrico Granata 592afe73ad Improve the 'type lookup' command such that it guesses to use the current's frame language as the one to start searching from.
llvm-svn: 263592
2016-03-15 21:50:51 +00:00
Tamas Berghammer 5b42c7aa25 Add support for DW_OP_push_object_address in dwarf expressions
Additionally fix the type of some dwarf expression where we had a
confusion between scalar and load address types after a dereference.

Differential revision: http://reviews.llvm.org/D17604

llvm-svn: 262014
2016-02-26 14:21:10 +00:00
Tamas Berghammer 72ac8a840f Handle the case when a variable is only valid in part of the enclosing scope
DWARF stores this information in the DW_AT_start_scope attribute. This
CL add support for this attribute and also changes the functions
displaying frame variables to only display the variables currently in
scope.

Differential revision: http://reviews.llvm.org/D17449

llvm-svn: 261858
2016-02-25 12:23:37 +00:00
Eugene Zelenko d70a6e71a9 Fix Clang-tidy modernize-use-nullptr warnings in some files in source/Target; other minor fixes.
llvm-svn: 261242
2016-02-18 18:52:47 +00:00
Jason Molenda 62e0681afb Add -Wimplicit-fallthrough command line option to clang in
the xcode project file to catch switch statements that have a
case that falls through unintentionally.

Define LLVM_FALLTHROUGH to indicate instances where a case has code
and intends to fall through.  This should be in llvm/Support/Compiler.h;
Peter Collingbourne originally checked in there (r237766), then
reverted (r237941) because he didn't have time to mark up all the
'case' statements that were intended to fall through.  I put together
a patch to get this back in llvm http://reviews.llvm.org/D17063 but
it hasn't been approved in the past week.  I added a new
lldb-private-defines.h to hold the definition for now.

Every place in lldb where there is a comment that the fall-through
is intentional, I added LLVM_FALLTHROUGH to silence the warning.
I haven't tried to identify whether the fallthrough is a bug or
not in the other places.

I haven't tried to add this to the cmake option build flags.
This warning will only work for clang.

This build cleanly (with some new warnings) on macosx with clang
under xcodebuild, but if this causes problems for people on other
configurations, I'll back it out.

llvm-svn: 260930
2016-02-16 04:14:33 +00:00
Siva Chandra b90168ff41 Fix a thinko in StackFrame::GetInScopeVariableList.
Reviewers: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D16745

llvm-svn: 259607
2016-02-02 23:49:41 +00:00
Mohit K. Bhakkad 8be7499507 [LLDB] Switch to assembly view if source is moved
Reviewers: clayborg, jingham, jasonmolenda.
Subscribers: jaydeep, bhushan, sagar, nitesh.jain,lldb-commits.
Differential Revision: http://reviews.llvm.org/D12877

llvm-svn: 254588
2015-12-03 04:56:16 +00:00
Enrico Granata 46252398f0 Fix up LLDB for a change in the way clang represents anonymous unions such that the 'frame variable' command can still find the members of such union as if they were top-level variables in the current scope
llvm-svn: 253613
2015-11-19 22:28:58 +00:00
Tamas Berghammer 25b9f7ebd3 Use eAddressClassCode for address lookup for opcodes for stack frames
It is required because of the following edge case on arm:

bx <addr>   Non-tail call in a no return function
[data-pool] Marked with $d mapping symbol

The return address of the function call will point to the data pool but
we have to treat it as code so the StackFrame can calculate the symbols
correctly.

Differential revision: http://reviews.llvm.org/D12556

llvm-svn: 246958
2015-09-07 09:58:09 +00:00
Dawn Perchik 009d110de4 Set the default language to use when evaluating to that of the frame's CU.
* Use the frame's context (instead of just the target's) when evaluating,
  so that the language of the frame's CU can be used to select the
  compiler and/or compiler options to use when parsing the expression.
  This allows for modules built with mixed languages to be parsed in
  the context of their frame. 
* Add all C and C++ language variants when determining the language options
  to set.
* Enable C++ language options when language is C or ObjC as a workaround since
  the expression parser uses features of C++ to capture values.
* Enable ObjC language options when language is C++ as a workaround for ObjC
  requirements.
* Disable C++11 language options when language is C++03.
* Add test TestMixedLanguages.py to check that the language being used
  for evaluation is that of the frame.
* Fix test TestExprOptions.py to check for C++11 instead of C++ since C++ has
  to be enabled for C, and remove redundant expr --language test for ObjC.
* Fix TestPersistentPtrUpdate.py to not require C++11 in C.

Reviewed by: clayborg, spyffe, jingham
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D11102

llvm-svn: 246829
2015-09-04 01:02:30 +00:00
Greg Clayton 99558cc424 Final bit of type system cleanup that abstracts declaration contexts into lldb_private::CompilerDeclContext and renames ClangType to CompilerType in many accessors and functions.
Create a new "lldb_private::CompilerDeclContext" class that will replace all direct uses of "clang::DeclContext" when used in compiler agnostic code, yet still allow for conversion to clang::DeclContext subclasses by clang specific code. This completes the abstraction of type parsing by removing all "clang::" references from the SymbolFileDWARF. The new "lldb_private::CompilerDeclContext" class abstracts decl contexts found in compiler type systems so they can be used in internal API calls. The TypeSystem is required to support CompilerDeclContexts with new pure virtual functions that start with "DeclContext" in the member function names. Converted all code that used lldb_private::ClangNamespaceDecl over to use the new CompilerDeclContext class and removed the ClangNamespaceDecl.cpp and ClangNamespaceDecl.h files.

Removed direct use of clang APIs from SBType and now use the abstract type systems to correctly explore types.

Bulk renames for things that used to return a ClangASTType which is now CompilerType:

    "Type::GetClangFullType()" to "Type::GetFullCompilerType()"
    "Type::GetClangLayoutType()" to "Type::GetLayoutCompilerType()"
    "Type::GetClangForwardType()" to "Type::GetForwardCompilerType()"
    "Value::GetClangType()" to "Value::GetCompilerType()"
    "Value::SetClangType (const CompilerType &)" to "Value::SetCompilerType (const CompilerType &)"
    "ValueObject::GetClangType ()" to "ValueObject::GetCompilerType()"
    many more renames that are similar.

llvm-svn: 245905
2015-08-24 23:46:31 +00:00
Paul Herman 10bc1a4e83 Fix resolution conflict between global and class static variables in C++
llvm-svn: 245381
2015-08-18 22:46:57 +00:00
Zachary Turner 1124045ac7 Don't #include "lldb-python.h" from anywhere.
Since interaction with the python interpreter is moving towards
being more isolated, we won't be able to include this header from
normal files anymore, all includes of it should be localized to
the python library which will live under source/bindings/API/Python
after a future patch.

None of the files that were including this header actually depended
on it anyway, so it was just a dead include in every single instance.

llvm-svn: 238581
2015-05-29 17:41:47 +00:00
Bruce Mitchener 11d86362ae Remove duplicated code for synthetic array members.
Summary:
The code for GetSyntheticArrayMemberFromPointer and
GetSyntheticArrayMemberFromArray was identical, so just collapse the
the methods into one.

Reviewers: granata.enrico, clayborg

Reviewed By: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D7911

llvm-svn: 230708
2015-02-26 23:55:39 +00:00
Jason Molenda c980fa92eb Change the default disassembly format again. First attempt at
changing it was in r219544 - after living on that for a few 
months, I wanted to take another crack at this.

The disassembly-format setting still exists and the old format
can be user specified with a setting like

${current-pc-arrow}${addr-file-or-load}{ <${function.name-without-args}${function.concrete-only-addr-offset-no-padding}>}: 

This patch was discussed in http://reviews.llvm.org/D7578

<rdar://problem/19726421>

llvm-svn: 229186
2015-02-13 23:24:21 +00:00
Greg Clayton 554f68d385 Get rid of Debugger::FormatPrompt() and replace it with the new FormatEntity class.
Why? Debugger::FormatPrompt() would run through the format prompt every time and parse it and emit it piece by piece. It also did formatting differently depending on which key/value pair it was parsing. 

The new code improves on this with the following features:
1 - Allow format strings to be parsed into a FormatEntity::Entry which can contain multiple child FormatEntity::Entry objects. This FormatEntity::Entry is a parsed version of what was previously always done in Debugger::FormatPrompt() so it is more efficient to emit formatted strings using the new parsed FormatEntity::Entry.
2 - Allows errors in format strings to be shown immediately when setting the settings (frame-format, thread-format, disassembly-format
3 - Allows auto completion by implementing a new OptionValueFormatEntity and switching frame-format, thread-format, and disassembly-format settings over to using it.
4 - The FormatEntity::Entry for each of the frame-format, thread-format, disassembly-format settings only replaces the old one if the format parses correctly
5 - Combines all consecutive string values together for efficient output. This means all "${ansi.*}" keys and all desensitized characters like "\n" "\t" "\0721" "\x23" will get combined with their previous strings
6 - ${*.script:} (like "${var.script:mymodule.my_var_function}") have all been switched over to use ${script.*:} "${script.var:mymodule.my_var_function}") to make the format easier to parse as I don't believe anyone was using these format string power user features.
7 - All key values pairs are defined in simple C arrays of entries so it is much easier to add new entries.

These changes pave the way for subsequent modifications where we can modify formats to do more (like control the width of value strings can do more and add more functionality more easily like string formatting to control the width, printf formats and more).

llvm-svn: 228207
2015-02-04 22:00:53 +00:00
Jason Molenda cf29675d95 Fix a corner case with the handling of noreturn functions.
If a noreturn function was the last function in a section,
we wouldn't correctly back up the saved-pc value into the
correct section leading to us showing the wrong function in
the backtrace.

Also add a backtrace test with an attempt to elicit this 
particular layout.  It happens to work out with clang -Os
but other compilers may not quite get the same layout I'm
getting at that opt setting.  We'll still be exercising the
basic noreturn handling in the unwinder even if we don't get
one function at the very end of a section.

<rdar://problem/16051613> 

llvm-svn: 221575
2014-11-08 05:38:17 +00:00
Enrico Granata 622be238eb Expose the type-info flags at the public API layer. These flags provide much more informational content to consumers of the LLDB API than the existing TypeClass. Part of the fix for rdar://18517593
llvm-svn: 220322
2014-10-21 20:52:14 +00:00
Jason Molenda aff1b357b0 Add a new disassembly-format specification so that the disassembler
output style can be customized.  Change the built-in default to be
more similar to gdb's disassembly formatting.

The disassembly-format for a gdb-like output is

${addr-file-or-load} <${function.name-without-args}${function.concrete-only-addr-offset-no-padding}>: 

The disassembly-format for the lldb style output is

{${function.initial-function}{${module.file.basename}`}{${function.name-without-args}}:\n}{${function.changed}\n{${module.file.basename}`}{${function.name-without-args}}:\n}{${current-pc-arrow} }{${addr-file-or-load}}: 

The two backticks in the lldb style formatter triggers the sub-expression evaluation in
CommandInterpreter::PreprocessCommand() so you can't use that one as-is ... changing to
use ' characters instead of ` would work around that.

<rdar://problem/9885398> 

llvm-svn: 219544
2014-10-10 23:07:36 +00:00
Jason Molenda 6a35470563 Add a mutex lock to StackFrame to protect race conditions for
updating its ivars.  We've had a lot of crash reports and careful
analysis shows that we've got multiple threads operating on the
same StackFrame objects, changing their m_sc and m_flags ivars.
<rdar://problem/18406111> 

llvm-svn: 218845
2014-10-02 01:08:16 +00:00
Bruce Mitchener aaa0ba31a9 Fix typos.
llvm-svn: 212553
2014-07-08 18:05:41 +00:00
Todd Fiala 6d1fbc9c56 Allow specification of no source display on stop.
See http://llvm.org/bugs/show_bug.cgi?id=20149 for details.

Change by Randy Smith.

llvm-svn: 212485
2014-07-07 20:47:24 +00:00
Saleem Abdulrasool 3985c8c646 sanitise sign comparisons
This is a mechanical change addressing the various sign comparison warnings that
are identified by both clang and gcc.  This helps cleanup some of the warning
spew that occurs during builds.

llvm-svn: 205390
2014-04-02 03:51:35 +00:00
Jason Molenda 99618476ad Add new ivars to StackFrame so it can represent a stack collected
at some point in the past.  We may have nothing more than a pc value
for this type of stack frame -- hopefully we'll have a pc and a
stop_id so we can track module loads and unloads over time and
symbolicate the pc at the correct point in time.

Also add a flag to indicate if the CFA for the frame is available
(a bit different from a CFA of LLDB_INVALID_ADDRESS) and also an
overall setting to indicate whether this is a history stack frame
or not.  A history stack frame may not have a CFA, it may not have
a register context, it may not have variables, it may not have a
frame pointer or a stack pointer.

<rdar://problem/15314068>

llvm-svn: 193987
2013-11-04 11:02:52 +00:00
Jason Molenda b57e4a1bc6 Roll back the changes I made in r193907 which created a new Frame
pure virtual base class and made StackFrame a subclass of that.  As
I started to build on top of that arrangement today, I found that it
wasn't working out like I intended.  Instead I'll try sticking with
the single StackFrame class -- there's too much code duplication to
make a more complicated class hierarchy sensible I think.

llvm-svn: 193983
2013-11-04 09:33:30 +00:00
Jason Molenda f23bf7432c Add a new base class, Frame. It is a pure virtual function which
defines a protocol that all subclasses will implement.  StackFrame
is currently the only subclass and the methods that Frame vends are
nearly identical to StackFrame's old methods.

Update all callers to use Frame*/Frame& instead of pointers to
StackFrames.

This is almost entirely a mechanical change that touches a lot of
the code base so I'm committing it alone.  No new functionality is
added with this patch, no new subclasses of Frame exist yet.

I'll probably need to tweak some of the separation, possibly moving
some of StackFrame's methods up in to Frame, but this is a good
starting point.

<rdar://problem/15314068>

llvm-svn: 193907
2013-11-02 02:23:02 +00:00
Jim Ingham 8ec10efc5d Mark the selected frame of the selected thread in backtraces.
<rdar://problem/15252474>

llvm-svn: 192989
2013-10-18 17:38:31 +00:00
Greg Clayton 57ee306789 Huge change to clean up types.
A long time ago we start with clang types that were created by the symbol files and there were many functions in lldb_private::ClangASTContext that helped. Later we create ClangASTType which contains a clang::ASTContext and an opauque QualType, but we didn't switch over to fully using it. There were a lot of places where we would pass around a raw clang_type_t and also pass along a clang::ASTContext separately. This left room for error.

This checkin change all type code over to use ClangASTType everywhere and I cleaned up the interfaces quite a bit. Any code that was in ClangASTContext that was type related, was moved over into ClangASTType. All code that used these types was switched over to use all of the new goodness.

llvm-svn: 186130
2013-07-11 22:46:58 +00:00
Michael Sartain c3ce7f2740 Add ${ansi.XX} parsing to lldb prompt, use-color setting, and -no-use-colors command line options.
settings set use-color [false|true]
settings set prompt "${ansi.bold}${ansi.fg.green}(lldb)${ansi.normal} "
also "--no-use-colors" on the command prompt

llvm-svn: 182609
2013-05-23 20:47:45 +00:00
Jason Molenda 7cd81c55c7 When lldb stops in a stack frame where we have source level information (file, line number), don't
print the disassembly context around $pc -- just print the filename and line number, even if we 
can't show the source code.  Previously if the source file was not available, lldb would print
the source filename & line number and assembly.  
<rdar://problem/13072951> 

llvm-svn: 180706
2013-04-29 09:59:31 +00:00
Jim Ingham 0f063ba6b4 Convert from the C-based LLVM Disassembler shim to the full MC Disassembler API's.
Calculate "can branch" using the MC API's rather than our hand-rolled regex'es.
As extra credit, allow setting the disassembly flavor for x86 based architectures to intel or att.

<rdar://problem/11319574>
<rdar://problem/9329275>

llvm-svn: 176392
2013-03-02 00:26:47 +00:00
Greg Clayton 5e3e1499c0 Backed out a hacky fix that is no longer needed.
llvm-svn: 176106
2013-02-26 17:59:39 +00:00
Greg Clayton 72310355ff <rdar://problem/13265297>
StackFrame assumes m_sc is additive, but m_sc can lose its target. So now the SymbolContext::Clear() method takes a bool that indicates if the target should be cleared. Modified all existing code to properly set the bool argument.

llvm-svn: 175953
2013-02-23 04:12:47 +00:00
Sean Callanan f4be227dc6 Fixed a case where a stack frame could lose track
of its own target.

<rdar://problem/13121412>

llvm-svn: 175794
2013-02-21 20:54:33 +00:00
Greg Clayton 4ef877f5e9 <rdar://problem/12560257>
Fixed zero sized arrays to work correctly. This will only happen once we get a clang that emits correct debug info for zero sized arrays. For now I have marked the TestStructTypes.py as an expected failure.

llvm-svn: 169465
2012-12-06 02:33:54 +00:00
Daniel Malea 93a64300f8 Fix Linux build warnings due to redefinition of macros:
- add new header lldb-python.h to be included before other system headers
- short term fix (eventually python dependencies must be cleaned up)

Patch by Matt Kopec!

llvm-svn: 169341
2012-12-05 00:20:57 +00:00
Daniel Malea d01b2953fa Resolve printf formatting warnings on Linux:
- use macros from inttypes.h for format strings instead of OS-specific types

Patch from Matt Kopec!

llvm-svn: 168945
2012-11-29 21:49:15 +00:00
Greg Clayton 75a0333bf8 <rdar://problem/12445557>
Make stack frames fix up their line table entries when the target has source remappings. Also rearranged how the m_sc.target_sp was filled in so it can be used during the StackFrame::GetSymbolContext(...) function.

llvm-svn: 168845
2012-11-29 00:53:06 +00:00
Jim Ingham 513c6bb88c Initial check-in of "fancy" inlined stepping. Doesn't do anything useful unless you switch LLDB_FANCY_INLINED_STEPPING to true. With that
on, basic inlined stepping works, including step-over of inlined functions.  But for some as yet mysterious reason i386 debugging gets an
assert and dies immediately.  So for now its off.

llvm-svn: 163044
2012-09-01 01:02:41 +00:00
Greg Clayton 1f7460716b <rdar://problem/11757916>
Make breakpoint setting by file and line much more efficient by only looking for inlined breakpoint locations if we are setting a breakpoint in anything but a source implementation file. Implementing this complex for a many reasons. Turns out that parsing compile units lazily had some issues with respect to how we need to do things with DWARF in .o files. So the fixes in the checkin for this makes these changes:
- Add a new setting called "target.inline-breakpoint-strategy" which can be set to "never", "always", or "headers". "never" will never try and set any inlined breakpoints (fastest). "always" always looks for inlined breakpoint locations (slowest, but most accurate). "headers", which is the default setting, will only look for inlined breakpoint locations if the breakpoint is set in what are consudered to be header files, which is realy defined as "not in an implementation source file". 
- modify the breakpoint setting by file and line to check the current "target.inline-breakpoint-strategy" setting and act accordingly
- Modify compile units to be able to get their language and other info lazily. This allows us to create compile units from the debug map and not have to fill all of the details in, and then lazily discover this information as we go on debuggging. This is needed to avoid parsing all .o files when setting breakpoints in implementation only files (no inlines). Otherwise we would need to parse the .o file, the object file (mach-o in our case) and the symbol file (DWARF in the object file) just to see what the compile unit was.
- modify the "SymbolFileDWARFDebugMap" to subclass lldb_private::Module so that the virtual "GetObjectFile()" and "GetSymbolVendor()" functions can be intercepted when the .o file contenst are later lazilly needed. Prior to this fix, when we first instantiated the "SymbolFileDWARFDebugMap" class, we would also make modules, object files and symbol files for every .o file in the debug map because we needed to fix up the sections in the .o files with information that is in the executable debug map. Now we lazily do this in the DebugMapModule::GetObjectFile()

Cleaned up header includes a bit as well.

llvm-svn: 162860
2012-08-29 21:13:06 +00:00
Greg Clayton 67cc06366c Reimplemented the code that backed the "settings" in lldb. There were many issues with the previous implementation:
- no setting auto completion
- very manual and error prone way of getting/setting variables
- tons of code duplication
- useless instance names for processes, threads

Now settings can easily be defined like option values. The new settings makes use of the "OptionValue" classes so we can re-use the option value code that we use to set settings in command options. No more instances, just "does the right thing".

llvm-svn: 162366
2012-08-22 17:17:09 +00:00
Greg Clayton 685c88c5a8 <rdar://problem/11870357>
Allow "frame variable" to find ivars without the need for "this->" or "self->".  

llvm-svn: 160211
2012-07-14 00:53:55 +00:00
Greg Clayton 53eb7ad2f7 <rdar://problem/11852100>
The "stop-line-count-after" and "stop-line-count-before" settings are broken. This fixes them.

llvm-svn: 160071
2012-07-11 20:33:48 +00:00
Enrico Granata 86cc982974 Massive enumeration name changes: a number of enums in ValueObject were not following the naming pattern
Changes to synthetic children:
 - the update(self): function can now (optionally) return a value - if it returns boolean value True, ValueObjectSyntheticFilter will not clear its caches across stop-points
   this should allow better performance for Python-based synthetic children when one can be sure that the child ValueObjects have not changed
 - making a difference between a synthetic VO and a VO with a synthetic value: now a ValueObjectSyntheticFilter will not return itself as its own synthetic value, but will (correctly)
   claim to itself be synthetic
 - cleared up the internal synthetic children architecture to make a more consistent use of pointers and references instead of shared pointers when possible
 - major cleanup of unnecessary #include, data and functions in ValueObjectSyntheticFilter itself
 - removed the SyntheticValueType enum and replaced it with a plain boolean (to which it was equivalent in the first place)
Some clean ups to the summary generation code
Centralized the code that clears out user-visible strings and data in ValueObject
More efficient summaries for libc++ containers

llvm-svn: 153061
2012-03-19 22:58:49 +00:00
Sean Callanan 226b70c154 Updated the revision of LLVM/Clang used by LLDB.
This takes two important changes:

- Calling blocks is now supported.  You need to
  cast their return values, but that works fine.

- We now can correctly run JIT-compiled
  expressions that use floating-point numbers.

Also, we have taken a fix that allows us to
ignore access control in Objective-C as in C++.

llvm-svn: 152286
2012-03-08 02:39:03 +00:00
Greg Clayton e72dfb321c <rdar://problem/10103468>
I started work on being able to add symbol files after a debug session
had started with a new "target symfile add" command and quickly ran into
problems with stale Address objects in breakpoint locations that had 
lldb_private::Section pointers into modules that had been removed or 
replaced. This also let to grabbing stale modules from those sections. 
So I needed to thread harded the Address, Section and related objects.

To do this I modified the ModuleChild class to now require a ModuleSP
on initialization so that a weak reference can created. I also changed
all places that were handing out "Section *" to have them hand out SectionSP.
All ObjectFile, SymbolFile and SymbolVendors were inheriting from ModuleChild
so all of the find plug-in, static creation function and constructors now
require ModuleSP references instead of Module *. 

Address objects now have weak references to their sections which can
safely go stale when a module gets destructed. 

This checkin doesn't complete the "target symfile add" command, but it
does get us a lot clioser to being able to do such things without a high
risk of crashing or memory corruption.

llvm-svn: 151336
2012-02-24 01:59:29 +00:00