to llvm-objdump. This section is created with -fembed-bitcode option.
This requires the use of libxar and the Cmake and lit support were crafted by
Chris Bieneman!
rdar://26202242
llvm-svn: 270491
when the object is in an archive to use something like libx.a(foo.o) as part of
the error message.
Also changed llvm-objdump and llvm-size to be like llvm-nm and ignore non-object
files in archives and not produce any error message.
To do this Archive::Child::getAsBinary() was changed from ErrorOr<...> to
Expected<...> then that was threaded up to its users.
Converting this interface to Expected<> from ErrorOr<> does involve
touching a number of places. To contain the changes for now the use of
errorToErrorCode() is still used in one place yet to be fully converted.
Again there some were bugs in the existing code that did not deal with the
old ErrorOr<> return values. So now with Expected<> since they must be
checked and the error handled, I added a TODO and a comments for those.
llvm-svn: 269784
load commands.
The existing test case in test/Object/macho-invalid.test for
macho-invalid-too-small-segment-load-command has a cmdsize of 55, while
being too small also it is not a multiple of 4. So when that check is added
this test case will produce a different error. So I constructed a new test case
that will trigger the intended error.
I also changed the error message to be consistent with the other malformed Mach-O
file error messages which prints the load command index. I also removed both
object_error::macho_load_segment_too_small and
object_error::macho_load_segment_too_many_sections from Object/Error.h
as they are not needed and can just use object_error::parse_failed and let the
error message string distinguish the specific error.
llvm-svn: 268652
Produce another specific error message for a malformed Mach-O file when a symbol’s
section index is more than the number of sections. The existing test case in test/Object/macho-invalid.test
for macho-invalid-section-index-getSectionRawName now reports the error with the message indicating
that a symbol at a specific index has a bad section index and that bad section index value.
Again converting interfaces to Expected<> from ErrorOr<> does involve
touching a number of places. Where the existing code reported the error with a
string message or an error code it was converted to do the same.
Also there some were bugs in the existing code that did not deal with the
old ErrorOr<> return values. So now with Expected<> since they must be
checked and the error handled, I added a TODO and a comment:
"// TODO: Actually report errors helpfully" and a call something like
consumeError(NameOrErr.takeError()) so the buggy code will not crash
since needed to deal with the Error.
llvm-svn: 268298
Two problems, 1) for the last 4 bytes it would print them as separate bytes not a word
and 2) it would print the same last byte for those bytes less than a word.
rdar://25938224
llvm-svn: 267819
Before we printed a warning to stderr and left the actual output stream in a
mess. This tries to print a .long or .short representation of what we saw (as
if there was a data-in-code directive).
This isn't guaranteed to restore synchronization in Thumb-mode (if the invalid
instruction was supposed to be 32-bits, we may be off-by-16 for the rest of the
function). But there's no certain way to deal with that, and it's invalid code
anyway (if the data really wasn't an instruction, the user can add proper
.data_in_code directives if they care)
llvm-svn: 267250
Only one consumer (llvm-objdump) actually cared about the fact that there were
two triples. Others were actively working around the fact that the Triple
returned by getArch might have been invalid. As for llvm-objdump, it needs to
be acutely aware of both Triples anyway, so being generic in the exposed API is
no benefit.
Also rename the version of getArch returning a Triple. Users were having to
pass an unwanted nullptr to disambiguate the two, which was nasty.
The only functional change here is that armv7m and armv7em object files no
longer crash llvm-objdump.
llvm-svn: 267249
I'm for some reason having a problem producing a test.
It should be the same as test/MC/X86/invalid_opcode.s,
but llvm-mc seems to ignore random bytes.
llvm-svn: 267225
Showed up in running on a large binary with the missing section. I could create a fake
test case if anyone really wants but the fix is pretty obvious.
rdar://25837034
llvm-svn: 267037
Produce another specific error message for a malformed Mach-O file when a symbol’s
string index is past the end of the string table. The existing test case in test/Object/macho-invalid.test
for macho-invalid-symbol-name-past-eof now reports the error with the message indicating
that a symbol at a specific index has a bad sting index and that bad string index value.
Again converting interfaces to Expected<> from ErrorOr<> does involve
touching a number of places. Where the existing code reported the error with a
string message or an error code it was converted to do the same. There is some
code for this that could be factored into a routine but I would like to leave that for
the code owners post-commit to do as they want for handling an llvm::Error. An
example of how this could be done is shown in the diff in
lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h which had a Check() routine
already for std::error_code so I added one like it for llvm::Error .
Also there some were bugs in the existing code that did not deal with the
old ErrorOr<> return values. So now with Expected<> since they must be
checked and the error handled, I added a TODO and a comment:
“// TODO: Actually report errors helpfully” and a call something like
consumeError(NameOrErr.takeError()) so the buggy code will not crash
since needed to deal with the Error.
Note there fixes needed to lld that goes along with this that I will commit right after this.
So expect lld not to built after this commit and before the next one.
llvm-svn: 266919
Removed some unused headers, replaced some headers with forward class declarations.
Found using simple scripts like this one:
clear && ack --cpp -l '#include "llvm/ADT/IndexedMap.h"' | xargs grep -L 'IndexedMap[<]' | xargs grep -n --color=auto 'IndexedMap'
Patch by Eugene Kosov <claprix@yandex.ru>
Differential Revision: http://reviews.llvm.org/D19219
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266595
Reenable reverted r265550 with endianness issue fixed. Variables of
endian-aware types such as ulittle32_t should be explicitly casted
to their natural equivalent types before passing it as vararg to
printf like functions (format in my case). Added lit config file
depending on AMDGPU target as the testcase uses assembler.
Differential revision: http://reviews.llvm.org/D16998
llvm-svn: 265645
Produce the first specific error message for a malformed Mach-O file describing
the problem instead of the generic message for object_error::parse_failed of
"Invalid data was encountered while parsing the file”. Many more good error
messages will follow after this first one.
This is built on Lang Hames’ great work of adding the ’Error' class for
structured error handling and threading Error through MachOObjectFile
construction. And making createMachOObjectFile return Expected<...> .
So to to get the error to the llvm-obdump tool, I changed the stack of
these methods to also return Expected<...> :
object::ObjectFile::createObjectFile()
object::SymbolicFile::createSymbolicFile()
object::createBinary()
Then finally in ParseInputMachO() in MachODump.cpp the error can
be reported and the specific error message can be printed in llvm-objdump
and can be seen in the existing test case for the existing malformed binary
but with the updated error message.
Converting these interfaces to Expected<> from ErrorOr<> does involve
touching a number of places. To contain the changes for now use of
errorToErrorCode() and errorOrToExpected() are used where the callers
are yet to be converted.
Also there some were bugs in the existing code that did not deal with the
old ErrorOr<> return values. So now with Expected<> since they must be
checked and the error handled, I added a TODO and a comment:
“// TODO: Actually report errors helpfully” and a call something like
consumeError(ObjOrErr.takeError()) so the buggy code will not crash
since needed to deal with the Error.
Note there is one fix also needed to lld/COFF/InputFiles.cpp that goes along
with this that I will commit right after this. So expect lld not to built
after this commit and before the next one.
llvm-svn: 265606
This reverts commit r265550. There're problems with endianness on dumping instruction bytes. Need to find out how to use support::ulittle32_t type properly.
llvm-svn: 265554
in the test suite. While this is not really an interesting tool and option to run
on a Mach-O file to show the symbol table in a generic libObject format
it shouldn’t crash.
The reason for the crash was in MachOObjectFile::getSymbolType() when it was
calling MachOObjectFile::getSymbolSection() without checking its return value
for the error case.
What makes this fix require a fair bit of diffs is that the method getSymbolType() is
in the class ObjectFile defined without an ErrorOr<> so I needed to add that all
the sub classes. And all of the uses needed to be updated and the return value
needed to be checked for the error case.
The MachOObjectFile version of getSymbolType() “can” get an error in trying to
come up with the libObject’s internal SymbolRef::Type when the Mach-O symbol
symbol type is an N_SECT type because the code is trying to select from the
SymbolRef::ST_Data or SymbolRef::ST_Function values for the SymbolRef::Type.
And it needs the Mach-O section to use isData() and isBSS to determine if
it will return SymbolRef::ST_Data.
One other possible fix I considered is to simply return SymbolRef::ST_Other
when MachOObjectFile::getSymbolSection() returned an error. But since in
the past when I did such changes that “ate an error in the libObject code” I
was asked instead to push the error out of the libObject code I chose not
to implement the fix this way.
As currently written both the COFF and ELF versions of getSymbolType()
can’t get an error. But if isReservedSectionNumber() wanted to check for
the two known negative values rather than allowing all negative values or
the code wanted to add the same check as in getSymbolAddress() to use
getSection() and check for the error then these versions of getSymbolType()
could return errors.
At the end of the day the error printed now is the generic “Invalid data was
encountered while parsing the file” for object_error::parse_failed. In the
future when we thread Lang’s new TypedError for recoverable error handling
though libObject this will improve. And where the added // Diagnostic(…
comment is, it would be changed to produce and error message
like “bad section index (42) for symbol at index 8” for this case.
llvm-svn: 264187
In executable and shared object ELF files, relocations in the file contain the final virtual address rather than section offset so this is adjusted to display section offset.
Differential revision: http://reviews.llvm.org/D15965
llvm-svn: 263971
It might be hard to recognize a hexadecimal number without '0x' prefix.
Besides that '0x' prefix corresponds to GNU objdump behaviour.
Differential Revision: http://reviews.llvm.org/D18207
llvm-svn: 263705
The PE TLS directory contains information about where the TLS data
resides in the image, what functions should be executed when threads are
created, etc.
llvm-svn: 263537
Summary:
This patch is provided in preparation for removing autoconf on 1/26. The proposal to remove autoconf on 1/26 was discussed on the llvm-dev thread here: http://lists.llvm.org/pipermail/llvm-dev/2016-January/093875.html
"I felt a great disturbance in the [build system], as if millions of [makefiles] suddenly cried out in terror and were suddenly silenced. I fear something [amazing] has happened."
- Obi Wan Kenobi
Reviewers: chandlerc, grosbach, bob.wilson, tstellarAMD, echristo, whitequark
Subscribers: chfast, simoncook, emaste, jholewinski, tberghammer, jfb, danalbert, srhines, arsenm, dschuff, jyknight, dsanders, joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D16471
llvm-svn: 258861
llvm-objdump when printing the Mach Header to print the unknown
cputype and cpusubtype fields as decimal instead of not printing
them at all. And change the test to check for that.
llvm-svn: 258826
When we arrive at the end of the function, the validation of
the object has been done already. In theory, so, we should never
arrive here with something broken as the object isn't mutated.
Practice sometimes proves theory to be wrong, so leave an assertion
instead, as suggested by David Blaikie, to catch bugs.
llvm-svn: 257570
to only print the first private header.
Which for Mach-O files only prints the Mach header and not the subsequent load
commands. Which is used by scripts to match what the darwin otool(1) with the
-h flag does without the -l flag.
For non-Mach-O files it has the same functionality as -private-headers (with
the trailing ’s’).
rdar://24158331
llvm-svn: 257548
A request has been made to the official registry, but an official value is
not yet available. This patch uses a temporary value in order to support
development. When an official value is recieved, the value of EM_WEBASSEMBLY
will be updated.
llvm-svn: 257517
LLVM MC has single methods which can handle the output of EH frame and DWARF CIE's and FDE's.
This code improves DWARFDebugFrame::parse to do the same for parsing.
This also allows llvm-objdump to support the --dwarf=frames option which objdump supports. This
option dumps the .eh_frame section using the new code in DWARFDebugFrame::parse.
http://reviews.llvm.org/D15535
Reviewed by Rafael Espindola.
llvm-svn: 256008
This code adds some simple decoding of the FDE's in an eh_frame.
There's still more to be done in terms of error handling and verification.
Also, we need to be able to decode the CFI's.
llvm-svn: 255550
This is the start of work to dump the contents of the eh_frame section.
It currently emits CIE entries. FDE entries will come later.
It also needs improved error checking which will follow soon.
http://reviews.llvm.org/D15502
Reviewed by Kevin Enderby and Lang Hames.
llvm-svn: 255546
Most linked executables do not have a symbol table in COFF.
However, it is pretty typical to have some export entries. Use those
entries to inform the disassembler about potential function definitions
and call targets.
llvm-svn: 253429
In `MachOObjectFile::getSymbolType` we currently always return `SymbolRef::ST_Function` for symbols from any section. In order for llvm-symbolizer to correctly symbolize Mach-O globals, symbols from data and BSS sections should return `SymbolRef::ST_Data`.
Differential Revision: http://reviews.llvm.org/D14576
llvm-svn: 252867
The needed lld matching changes to be submitted immediately next,
but this revision will cause lld failures with this alone which is expected.
This removes the eating of the error in Archive::Child::getSize() when the characters
in the size field in the archive header for the member is not a number. To do this we
have all of the needed methods return ErrorOr to push them up until we get out of lib.
Then the tools and can handle the error in whatever way is appropriate for that tool.
So the solution is to plumb all the ErrorOr stuff through everything that touches archives.
This include its iterators as one can create an Archive object but the first or any other
Child object may fail to be created due to a bad size field in its header.
Thanks to Lang Hames on the changes making child_iterator contain an
ErrorOr<Child> instead of a Child and the needed changes to ErrorOr.h to add
operator overloading for * and -> .
We don’t want to use llvm_unreachable() as it calls abort() and is produces a “crash”
and using report_fatal_error() to move the error checking will cause the program to
stop, neither of which are really correct in library code. There are still some uses of
these that should be cleaned up in this library code for other than the size field.
The test cases use archives with text files so one can see the non-digit character,
in this case a ‘%’, in the size field.
These changes will require corresponding changes to the lld project. That will be
committed immediately after this change. But this revision will cause lld failures
with this alone which is expected.
llvm-svn: 252192
in the size field in the archive header for the member is not a number. To do this we
have all of the needed methods return ErrorOr to push them up until we get out of lib.
Then the tools and can handle the error in whatever way is appropriate for that tool.
So the solution is to plumb all the ErrorOr stuff through everything that touches archives.
This include its iterators as one can create an Archive object but the first or any other
Child object may fail to be created due to a bad size field in its header.
Thanks to Lang Hames on the changes making child_iterator contain an
ErrorOr<Child> instead of a Child and the needed changes to ErrorOr.h to add
operator overloading for * and -> .
We don’t want to use llvm_unreachable() as it calls abort() and is produces a “crash”
and using report_fatal_error() to move the error checking will cause the program to
stop, neither of which are really correct in library code. There are still some uses of
these that should be cleaned up in this library code for other than the size field.
Also corrected the code where the size gets us to the “at the end of the archive”
which is OK but past the end of the archive will return object_error::parse_failed now.
The test cases use archives with text files so one can see the non-digit character,
in this case a ‘%’, in the size field.
llvm-svn: 250906
malformed Mach-O file that caused a crash. This was because of an
assert where the code was incorrectly attempting to parse relocation
entries off of the sections and the filetype was not an MH_OBJECT.
rdar://22983603
llvm-svn: 249921
from malformed Mach-O files that caused crashes. The first because the
offset in a dyld bind table entry was out of range. The second because their
was no image info section and the routine printing it did not have the
need check to see the section did not exist.
rdar://22983603
llvm-svn: 249845
from malformed Mach-O files that caused a crash because of a
section header had a size that extended past the end of the file.
rdar://22983603
llvm-svn: 249768
llvm-nm only needs the target to parse module level assembly in bitcode. It doesn't need a disassembler or codegen.
llvm-objdump needs to be able to disassemble a file, but doesn't need asm parsers or codegen.
This reduces the sizes of these tools by a few MB each, depending on how many backends are linked in.
llvm-svn: 249632
from malformed Mach-O files that caused crashes.
We recently got about 700 malformed Mach-O files which we have
been using the improve the robustness of tools that deal with reading
data from object files. These resulted in about 20 small bug fixes to
the darwin based tools.
The goal here is to also improve the robustness of llvm-objdump and
this is the first two fixes. In talking with Tim Northover the approach
we thought might be best is to:
1) Only include tests for the malformed Mach-O files that cause crashes
(not all 700+ tests).
2) The test should only contain the command line option that caused the
crash and not all the others that don’t matter.
3) There should be only one line for the FileCheck that is past the point
of the crash if possible and if possible indicates the malformation.
Again the goal is to fix crashes and not so much care about how the
printing of malformed data comes out.
Tim also suggested if we really wanted to add test cases for all 700+
malformed Mach-O files putting them in the regression tests might be
an option. But many of these do not cause crashes.
llvm-svn: 249479
AArch64 uses $d* and $x* to interleave between text and data.
llvm-objdump didn't know about this so it ended up printing garbage.
This patch is a first step towards a solution of the problem.
Differential Revision: http://reviews.llvm.org/D13360
llvm-svn: 249083
Summary:
This is the first patch in the series to migrate Triple's (which are ambiguous)
to TargetTuple's (which aren't).
For the moment, TargetTuple simply passes all requests to the Triple object it
holds. Once it has replaced Triple, it will start to implement the interface in
a more suitable way.
This change makes some changes to the public C++ API. In particular,
InitMCSubtargetInfo(), createMCRelocationInfo(), and createMCSymbolizer()
now take TargetTuples instead of Triples. The other public C++ API's have
been left as-is for the moment to reduce patch size.
This commit also contains a trivial patch to clang to account for the C++ API
change. Thanks go to Pavel Labath for fixing LLDB for me.
Reviewers: rengolin
Subscribers: jyknight, dschuff, arsenm, rampitec, danalbert, srhines, javed.absar, dsanders, echristo, emaste, jholewinski, tberghammer, ted, jfb, llvm-commits, rengolin
Differential Revision: http://reviews.llvm.org/D10969
llvm-svn: 247692
Summary:
This is the first patch in the series to migrate Triple's (which are ambiguous)
to TargetTuple's (which aren't).
For the moment, TargetTuple simply passes all requests to the Triple object it
holds. Once it has replaced Triple, it will start to implement the interface in
a more suitable way.
This change makes some changes to the public C++ API. In particular,
InitMCSubtargetInfo(), createMCRelocationInfo(), and createMCSymbolizer()
now take TargetTuples instead of Triples. The other public C++ API's have
been left as-is for the moment to reduce patch size.
This commit also contains a trivial patch to clang to account for the C++ API
change.
Reviewers: rengolin
Subscribers: jyknight, dschuff, arsenm, rampitec, danalbert, srhines, javed.absar, dsanders, echristo, emaste, jholewinski, tberghammer, ted, jfb, llvm-commits, rengolin
Differential Revision: http://reviews.llvm.org/D10969
llvm-svn: 247683
After r244870 flush() will only compare two null pointers and return,
doing nothing but wasting run time. The call is not required any more
as the stream and its SmallString are always in sync.
Thanks to David Blaikie for reviewing.
llvm-svn: 244928
Previously we kept going on partly corrupted input, which might result
in garbage being printed, or even worse, random crashes.
Rafael mentioned that this is the GNU behavior as well, but after some
discussion we both agreed it's probably better to emit a reasonable
error message and exit. As a side-effect of this commit, now we don't
rely on global state for error codes anymore. objdump was the last tool
in the toolchain which needed to be converted. Hopefully the old behavior
won't sneak into the tree again.
llvm-svn: 244019
Don't let the disassembler pick call <.text> if a function happens to
live at the start of the section by only using function symbols.
llvm-svn: 241830
option that works with all object container formats.
Now that clang modules/PCH are object containers this option is useful to
to construct pipes like
llvm-objdump -raw-clang-ast foo.pcm | llvm-bcanalyzer -
to inspect the AST contents in a PCH container.
Will be tested via clang.
Belatedly addresses review feedback for r233390.
llvm-svn: 241659
getSymbolValue now returns a value that in convenient for most callers:
* 0 for undefined
* symbol size for common symbols
* offset/address for symbols the rest
Code that needs something more specific can check getSymbolFlags.
llvm-svn: 241605
This function can really fail since the string table offset can be out of
bounds.
Using ErrorOr makes sure the error is checked.
Hopefully a lot of the boilerplate code in tools/* can go away once we have
a diagnostic manager in Object.
llvm-svn: 241297
This also improves the logic of what is an error:
* getSection(uint_32): only return an error if the index is out of bounds. The
index 0 corresponds to a perfectly valid entry.
* getSection(Elf_Sym): Returns null for symbols that normally don't have
sections and error for out of bound indexes.
In many places this just moves the report_fatal_error up the stack, but those
can then be fixed in smaller patches.
llvm-svn: 241156
This moves the error checking for string tables to getStringTable which returns
an ErrorOr<StringRef>.
This improves error checking, makes it uniform across all string tables and
makes it possible to check them once instead of once per name.
llvm-svn: 240950
It was a fairly broken concept for an ELF only class.
An ELF file can have two symbol tables, but they have exactly the same
format. There is no concept of a dynamic or a static symbol. Storing this
on the iterator also makes us do more work per symbol than necessary. To fetch
a name we would:
* Find if we had a static or a dynamic symbol.
* Look at the corresponding symbol table and find the string table section.
* Look at the string table section to fetch its contents.
* Compute the name as a substring of the string table.
All but the last step can be done per symbol table instead of per symbol. This
is a step in that direction.
llvm-svn: 240939
This is still a really odd function. Most calls are in object format specific
contexts and should probably be replaced with a more direct query, but at least
now this is not too obnoxious to use.
llvm-svn: 240777
COFF and MachO only define symbol sizes for common symbols. Reflect that
in the class hierarchy by having a method for common symbols only in the base
and a general one in ELF.
This avoids the need of using a magic value for the size, which had a few
problems
* Most callers didn't check for it.
* The ones that did could not tell the magic value from a file actually having
that value.
llvm-svn: 240529
Only common symbol on MachO and COFF have a size.
For COFF we already had a custom format.
For MachO, there is no native objdump and we were printing it as ELF. Now
we only print the sizes for symbols that actually have them.
llvm-svn: 240422
Summary:
That way llvm-objdump can rely on it without adding an extra dependency
on CodeGen.
This change duplicates the FaultKind enum and the code that serializes
it to a string. I could not figure out a way to get around this without
adding a new dependency to Object
Reviewers: rafael, ab
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D10619
llvm-svn: 240364
Summary:
The parser is exercised by llvm-objdump using -print-fault-maps. As is
probably obvious, the code itself was "heavily inspired" by
http://reviews.llvm.org/D10434.
Reviewers: reames, atrick, JosephTremoulet
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D10491
llvm-svn: 240304
make_error_code(object_error) is slow because object::object_category()
uses a ManagedStatic variable. But the real problem is that the function is
called too frequently. This patch uses std::error_code() instead of
object_error::success. In most cases, we return "success", so this patch
reduces number of function calls to that function.
http://reviews.llvm.org/D10333
llvm-svn: 239409
* If the input file is missing;
* If the type of input object file can't be recognized;
* If the object file can't be parsed correctly.
llvm-svn: 239065
Summary:
Now users don't have to manually deal with getFirstLoadCommandInfo() /
getNextLoadCommandInfo(), calculate the number of load segments, etc.
No functionality change.
Test Plan: regression test suite
Reviewers: rafael, lhames, loladiro
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D10144
llvm-svn: 238983
The ELF spec is very clear:
-----------------------------------------------------------------------------
If the value is non-zero, it represents a string table index that gives the
symbol name. Otherwise, the symbol table entry has no name.
--------------------------------------------------------------------------
In particular, a st_name of 0 most certainly doesn't mean that the symbol has
the same name as the section.
llvm-svn: 238899
Summary:
This supersedes http://reviews.llvm.org/D4010, hopefully properly
dealing with the JIT case and also adds an actual test case.
DwarfContext was basically already usable for the JIT (and back when
we were overwriting ELF files it actually worked out of the box by
accident), but in order to resolve relocations correctly it needs
to know the load address of the section.
Rather than trying to get this out of the ObjectFile or requiring
the user to create a new ObjectFile just to get some debug info,
this adds the capability to pass in that info directly.
As part of this I separated out part of the LoadedObjectInfo struct
from RuntimeDyld, since it is now required at a higher layer.
Reviewers: lhames, echristo
Reviewed By: echristo
Subscribers: vtjnash, friss, rafael, llvm-commits
Differential Revision: http://reviews.llvm.org/D6961
llvm-svn: 237961
option to print the archive headers using raw numeric values. Also add the -archive-member-offsets
for use with these to also trigger printing of the offset of the archive member from the start
of the archive.
llvm-svn: 236252
This will enable us to create a PDBContext so as to expose some
amount of debug info functionality through a common interace.
Differential Revision: http://reviews.llvm.org/D9205
Reviewed by: Alexey Samsonov
llvm-svn: 235612
