Summary:
This commit adds the glue code necessary to integrate the
SymbolFileBreakpad into the plugin system. Most of the methods are
stubbed out. The only method implemented method is AddSymbols, which
parses the PUBLIC "section" of the breakpad "object file", and fills out
the Module's symtab.
To enable testing this, I've made two additional changes:
- dump Symtab from the SymbolVendor class. The symtab was already being
dumped as a part of the object file dump, but that happened before
symbol vendor kicked in, so it did not reflect any symbols added
there.
- add ability to explicitly specify the external symbol file in
lldb-test (so that the object file could be linked with the breakpad
symbol file). To make things simpler, I've changed lldb-test from
consuming multiple inputs (and dumping their symbols) to having it
just process a single file per invocation. This was not a problem
since everyone was using it that way already.
Reviewers: clayborg, zturner, lemo, markmentovai, amccarth
Subscribers: mgorny, lldb-commits
Differential Revision: https://reviews.llvm.org/D56173
llvm-svn: 350924
Typedefs are represented as S_UDT records in the globals stream. This
creates a strange situation where "types" are actually represented as
"symbols", so they need special handling.
In order to test this, we don't just use lldb and print out some
variables causing the AST to get created, because variables whose type
is a typedef will have debug info referencing the original type, not the
typedef. So we use lldb-test instead which will parse all debug info in
the entire file. This exposed some problems with lldb-test and the
native reader, mainly that certain types of obscure symbols which we can
find when iterating every single record would trigger crashes. These
have been fixed as well so that lldb-test can be used to test this
functionality.
Differential Revision: https://reviews.llvm.org/D56461
llvm-svn: 350888
This reverts commit r350802 because the test fails on windows. This
happens because we treat the paths as windows paths even though they
have linux path separators in the asm file. That results in wrong paths
being computed (\tmp\tmp\a.c instead of /tmp/a.c).
Reverting until I can figure out what to do with this.
llvm-svn: 350810
Summary:
The motivation for this is being able to write tests for the upcoming
breakpad line table parser, but this could be useful for testing the
low-level workings of any line table format. Or simply for viewing the
line table information with more detail (the brief format doesn't
include any of the flags for end_of_prologue and similar).
I've also removed the load_addresses argument from the
DumpCompileUnitLineTable function, as it wasn't being used anywhere.
Reviewers: clayborg, zturner
Subscribers: JDevlieghere, lldb-commits
Differential Revision: https://reviews.llvm.org/D56315
llvm-svn: 350802
CHECK-DAG can't really be mixed with CHECK-NEXT statements because
each non DAG check sets a new search-origin for following CHECK-DAG
statements. This was passing by coincidence before, but a benign
change in the way we process symbols caused the order of the output
to be different, which triggered this test to fail.
This change makes the test resilient against ordering problems by
running a separate invocation of FileCheck for each function that
we want to test.
Note that with the Native PDB reader, we have full control over
the ordering that symbols are processed in, so we don't have
to worry about different machines returning things in different
orders due to different DIA SDK versions.
llvm-svn: 350773
ParseDeclsForContext was originally created to serve the very specific
case where the context is a function block. It was never intended to be
used for arbitrary DeclContexts, however due to the generic name, the
DWARF and PDB plugins implemented it in this way "just in case". Then,
lldb-test came along and decided to use it in that way.
Related to this, there are a set of functions in the SymbolFile class
interface whose requirements and expectations are not documented. For
example, if you call ParseCompileUnitFunctions, there's an inherent
requirement that you create entries in the underlying clang AST for
these functions as well as their signature types, because in order to
create an lldb_private::Function object, you have to pass it a
CompilerType for the parameter representing the signature.
On the other hand, there is no similar requirement (either inherent or
documented) if one were to call ParseDeclsForContext. Specifically, if
one calls ParseDeclsForContext, and some variable declarations, types,
and other things are added to the clang AST, is it necessary to create
lldb::Variable, lldb::Type, etc objects representing them? Nobody knows.
There is, however, an accidental requirement, because since all of the
plugins implemented this just in case, lldb-test came along and used
ParsedDeclsForContext, and then wrote check lines that depended on this.
When I went to try and implemented the NativePDB reader, I did not
adhere to this (in fact, from a layering perspective I went out of my
way to avoid it), and as a result the existing DIA PDB tests don't work
when the native PDB reader is enabled, because they expect that calling
ParseDeclsForContext will modify the *module's* view of symbols, and not
just the internal AST.
All of this confusion, however, can be avoided if we simply stick to
using ParseDeclsForContext for its original intended use case (blocks),
and use a different function (ParseAllDebugSymbols) for its intended use
case which is, unsuprisingly, to parse all the debug symbols (which is
all lldb-test really wanted to do anyway).
In the future, I would like to change ParseDeclsForContext to
ParseDeclsForFunctionBlock, then delete all of the dead code inside that
handles other types of DeclContexts (and probably even assert if the
DeclContext is anything other than a block).
A few PDB tests needed to be fixed up as a result of this, and this also
exposed a couple of bugs in the DIA PDB reader (doesn't matter much
since it should be going away soon, but worth mentioning) where the
appropriate AST entries weren't being created always.
Differential Revision: https://reviews.llvm.org/D56418
llvm-svn: 350764
This is a first step towards getting lldb-test symbols working
with the native plugin. There is a remaining issue, which is
that the plugin expects that ParseDeclsForContext will also
create lldb symbols rather than just the decls, but the native
pdb plugin doesn't currently do this. This will be addressed
in a followup patch.
llvm-svn: 350243
A Previous patch added support for creating VarDecls for global
variables. This patch updates this test to be more strict and
actually check these, not just the types.
llvm-svn: 350242
There were several problems preventing this from working. The
first is that when the PDB had an absolute path to the main
source file, we would construct an invalid path by prepending the
compilation directory to it anyway. So we needed to check if the
path is already absolute first.
Second, LLDB assumes that the zero'th item in the support file list
is the main compilation unit. We were respecting this requirement,
but LLDB *also* requires that file to appear somewhere in the list
starting from index 1 as well. So the main compilation file should
appear in the support file list twice. And when parsing a line
table, it expects the LineEntry records to be constructed using
the 1-based index. With these two fixes we can now set breakpoints
by file and line using the native PDB reader.
llvm-svn: 350240
Summary:
r346165 introduced a bug, where we would fail to parse the size of an
array if that size happened to match an existing die offset.
The logic was:
if (DWARFDIE count = die.GetReferencedDie(DW_AT_count))
num_elements = compute_vla_size(count);
else
num_elements = die.GetUsigned(DW_AT_count); // a fixed-size array
The problem with this logic was that GetReferencedDie did not take the
form class of the attribute into account, and would happily return a die
reference for any form, if its value happened to match some die.
As this behavior is inconsistent with how llvm's DWARFFormValue class
operates, I chose to fix the problem by making our version of this class
match the llvm behavior. For this to work, I had to add an explicit form
class check to the .apple_XXX tables parsing code, because they do
(incorrectly?) use data forms as die references.
Reviewers: aprantl, clayborg
Subscribers: JDevlieghere, lldb-commits
Differential Revision: https://reviews.llvm.org/D55991
llvm-svn: 350086
Previously we would create these for local variables but not for
global variables.
Also updated existing tests which created global variables to check
for them in the resulting AST.
llvm-svn: 349854
We had a use after free where we were assigning the result of a function
that returned a string to a StringRef. After fixing this use after
free, one of the DIA PDB tests now passes with the native PDB reader,
so we enable the test under native mode as well. The goal is to
eventually make all the tests pass under both, at which point we can
disable them all under DIA mode.
llvm-svn: 349673
We reconstruct the AST hierarchy by trying to hack up a mangled
name for the parent type using the child type's mangled name.
This was failing for enums because their tag type is represented
with two letters ("W4") instead of one letter ("T", "U", etc) as
it is with classes, structs, and unions. After accounting for
this we can now correctly determine when an enum is nested
inside of a namespace or a class.
llvm-svn: 349565
Previously the code that parsed debug info to create lldb's Symbol
objects such as Variable, Type, Function, etc was tightly coupled
to the AST reconstruction code. This made it difficult / impossible
to implement functions such as ParseDeclsForContext() that were only
supposed to be operating on clang AST's. By splitting these apart,
the logic becomes much cleaner and we have a clear separation of
responsibilities.
llvm-svn: 349383
Since we're actually running an executable on the host now, different
versions of Windows could load different system libraries, so we need
to regex out the number of loaded modules.
llvm-svn: 349175
This patch adds support for parsing and evaluating local variables.
using the native pdb plugin.
Differential Revision: https://reviews.llvm.org/D55575
llvm-svn: 349067
Previously we would create an lldb::Function object for each function
parsed, but we would not add these to the clang AST. This is a first
step towards getting local variable support working, as we first need an
AST decl so that when we create local variable entries, they have the
proper DeclContext.
Differential Revision: https://reviews.llvm.org/D55384
llvm-svn: 348631
Summary:
This patch contains several small fixes, which makes it possible to evaluate
expressions on Windows using information from PDB. The changes are:
- several sanitize checks;
- make IRExecutionUnit::MemoryManager::getSymbolAddress to not return a magic
value on a failure, because callers wait 0 in this case;
- entry point required to be a file address, not RVA, in the ObjectFilePECOFF;
- do not crash on a debuggee second chance exception - it may be an expression
evaluation crash. Also fix detection of "crushed" threads in tests;
- create parameter declarations for functions in AST to make it possible to call
debugee functions from expressions;
- relax name searching rules for variables, functions, namespaces and types. Now
it works just like in the DWARF plugin;
- fix endless recursion in SymbolFilePDB::ParseCompileUnitFunctionForPDBFunc.
Reviewers: zturner, asmith, stella.stamenova
Reviewed By: stella.stamenova, asmith
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D53759
llvm-svn: 348136
This adds a script called build.py as well as a lit substitution
called %build that we can use to invoke it. The idea is that
this allows a lit test to build test inferiors without having
to worry about architecture / platform specific differences,
command line syntax, finding / configurationg a proper toolchain,
and other issues. They can simply write something like:
%build --arch=32 -o %t.exe %p/Inputs/foo.cpp
and it will just work. This paves the way for being able to
run lit tests with multiple configurations, platforms, and
compilers with a single test.
Differential Revision: https://reviews.llvm.org/D54914
llvm-svn: 348058
This reverts commit dec87759523b2f22fcff3325bc2cd543e4cda0e7.
This commit caused the tests on Windows to run forever rather than complete.
Reverting until the commit can be fixed to not stall.
llvm-svn: 348009
Summary:
This patch contains several small fixes, which makes it possible to evaluate
expressions on Windows using information from PDB. The changes are:
- several sanitize checks;
- make IRExecutionUnit::MemoryManager::getSymbolAddress to not return a magic
value on a failure, because callers wait 0 in this case;
- entry point required to be a file address, not RVA, in the ObjectFilePECOFF;
- do not crash on a debuggee second chance exception - it may be an expression
evaluation crash;
- create parameter declarations for functions in AST to make it possible to call
debugee functions from expressions;
- relax name searching rules for variables, functions, namespaces and types. Now
it works just like in the DWARF plugin;
- fix endless recursion in SymbolFilePDB::ParseCompileUnitFunctionForPDBFunc.
Reviewers: zturner, asmith, stella.stamenova
Reviewed By: stella.stamenova, asmith
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D53759
llvm-svn: 347962
Recently I tried to port LLDB's lit configuration files over to use a
on the surface, but broke some cases that weren't broken before and also
exposed some additional problems with the old approach that we were just
getting lucky with.
When we set up a lit environment, the goal is to make it as hermetic as
possible. We should not be relying on PATH and enabling the use of
arbitrary shell commands. Instead, only whitelisted commands should be
allowed. These are, generally speaking, the lit builtins such as echo,
cd, etc, as well as anything for which substitutions have been
explicitly set up for. These substitutions should map to the build
output directory, but in some cases it's useful to be able to override
this (for example to point to an installed tools directory).
This is, of course, how it's supposed to work. What was actually
happening is that we were bringing in PATH and LD_LIBRARY_PATH and then
just running the given run line as a shell command. This led to problems
such as finding the wrong version of clang-cl on PATH since it wasn't
even a substitution, and flakiness / non-determinism since the
environment the tests were running in would change per-machine. On the
other hand, it also made other things possible. For example, we had some
tests that were explicitly running cl.exe and link.exe instead of
clang-cl and lld-link and the only reason it worked at all is because it
was finding them on PATH. Unfortunately we can't entirely get rid of
these tests, because they support a few things in debug info that
clang-cl and lld-link don't (notably, the LF_UDT_MOD_SRC_LINE record
which makes some of the tests fail.
The high level changes introduced in this patch are:
1. Removal of functionality - The lit test suite no longer respects
LLDB_TEST_C_COMPILER and LLDB_TEST_CXX_COMPILER. This means there is no
more support for gcc, but nobody was using this anyway (note: The
functionality is still there for the dotest suite, just not the lit test
suite). There is no longer a single substitution %cxx and %cc which maps
to <arbitrary-compiler>, you now explicitly specify the compiler with a
substitution like %clang or %clangxx or %clang_cl. We can revisit this
in the future when someone needs gcc.
2. Introduction of the LLDB_LIT_TOOLS_DIR directory. This does in spirit
what LLDB_TEST_C_COMPILER and LLDB_TEST_CXX_COMPILER used to do, but now
more friendly. If this is not specified, all tools are expected to be
the just-built tools. If it is specified, the tools which are not
themselves being tested but are being used to construct and run checks
(e.g. clang, FileCheck, llvm-mc, etc) will be searched for in this
directory first, then the build output directory.
3. Changes to core llvm lit files. The use_lld() and use_clang()
functions were introduced long ago in anticipation of using them in
lldb, but since they were never actually used anywhere but their
respective problems, there were some issues to be resolved regarding
generality and ability to use them outside their project.
4. Changes to .test files - These are all just replacing things like
clang-cl with %clang_cl and %cxx with %clangxx, etc.
5. Changes to lit.cfg.py - Previously we would load up some system
environment variables and then add some new things to them. Then do a
bunch of work building out our own substitutions. First, we delete the
system environment variable code, making the environment hermetic. Then,
we refactor the substitution logic into two separate helper functions,
one which sets up substitutions for the tools we want to test (which
must come from the build output directory), and another which sets up
substitutions for support tools (like compilers, etc).
6. New substitutions for MSVC -- Previously we relied on location of
MSVC by bringing in the entire parent's PATH and letting
subprocess.Popen just run the command line. Now we set up real
substitutions that should have the same effect. We use PATH to find
them, and then look for INCLUDE and LIB to construct a substitution
command line with appropriate /I and /LIBPATH: arguments. The nice thing
about this is that it opens the door to having separate %msvc-cl32 and
%msvc-cl64 substitutions, rather than only requiring the user to run
vcvars first. Because we can deduce the path to 32-bit libraries from
64-bit library directories, and vice versa. Without these substitutions
this would have been impossible.
Differential Revision: https://reviews.llvm.org/D54567
llvm-svn: 347216
Summary:
While parsing a childless compile unit DIE we could crash if the DIE was
followed by any extra data (such as a superfluous end-of-children
marker). This happened because the break-on-depth=0 check was performed
only when parsing the null DIE, which was not correct because with a
childless root DIE, we could reach the end of the unit without ever
encountering the null DIE.
If the compile unit contribution ended directly after the CU DIE,
everything would be fine as we would terminate parsing due to reaching
EOF. However, if the contribution contained extra data (perhaps a
superfluous end-of-children marker), we would crash because we would
treat that data as the begging of another compile unit.
This fixes the crash by moving the depth=0 check to a more generic
place, and also adds a regression test.
Reviewers: clayborg, jankratochvil, JDevlieghere
Subscribers: lldb-commits
Differential Revision: https://reviews.llvm.org/D54417
llvm-svn: 346849
clang-cl does not emit these, but MSVC does, so we need to be able to
handle them.
Because clang-cl does not generate them, it was a bit hard to write a
test. So what I had to do was get an PDB file with some S_CONSTANT
records in using cl and link, dump it using llvm-pdbutil dump -globals
-sym-data to get the bytes of the records, generate the same object file
using clang-cl but with -S to emit an assembly file, and replace all the
S_LDATA32 records with the bytes of the S_CONSTANT records. This way, we
can compile the file using llvm-mc and link it with lld-link.
Differential Revision: https://reviews.llvm.org/D54452
llvm-svn: 346787
In a previous patch, we pre-processed the TPI stream in order to build
the reverse mapping from nested type -> parent type so that we could
accurately reconstruct a DeclContext hierarchy.
However, there were some issues. An LF_NESTTYPE record is really just a
typedef, so although it happens to be used to indicate the name of the
nested type and referring to the global record which defines the type,
it is also used for every other kind of nested typedef. When we rebuild
the DeclContext hierarchy, we want it to be as accurate as possible,
which means that if we have something like:
struct A {
struct B {};
using C = B;
};
We don't want to create two CXXRecordDecls in the AST each with the
exact same definition. We just want to create one for B and then
define C as an alias to B. Previously, however, it would not be able
to distinguish between the two cases and it would treat A::B and
A::C as being two classes each with separate definitions. We address
the first half of improving the pre-processing logic so that only
actual definitions are treated this way.
Later, in a followup patch, we can handle the case of nested
typedefs since we're already going to be enumerating the field list
anyway and this patch introduces the general framework for
distinguishing between the two cases.
Differential Revision: https://reviews.llvm.org/D54357
llvm-svn: 346786
This patch processes the case of retrieving a virtual base when the object is
already read from the debuggee memory.
To achieve that ValueObject::GetCPPVTableAddress was removed and was
reimplemented in ClangASTContext (because access to the process is needed to
retrieve the VTable pointer in general, and because this is the only place that
used old version of ValueObject::GetCPPVTableAddress).
This patch allows to use real object's VTable instead of searching virtual bases
by offsets restored by MicrosoftRecordLayoutBuilder. PDB has no enough info to
restore VBase offsets properly, so we have to read real VTable instead.
Differential revision: https://reviews.llvm.org/D53506
llvm-svn: 346669
This patch removes the comments grouping header includes. They were
added after running IWYU over the LLDB codebase. However they add little
value, are often outdates and burdensome to maintain.
llvm-svn: 346626
This was originally submitted in a patch which fixed two unrelated
bugs at the same time. This portion of the fix was reverted because
it broke several other things. However, the fix employed originally
was totally wrong, and attempted to change something in the ValueObject
printer when actually the bug was in the NativePDB plugin. We need
to mark forward enum decls as having external storage, otherwise
we won't be asked to complete them when the time comes. This patch
implements the proper fix, and updates tests accordingly.
llvm-svn: 346517
Bitfields are represented as LF_MEMBER records whose TypeIndex
points to an LF_BITFIELD record that describes the bit width,
bit offset, and underlying type of the bitfield. All we need to
do is resolve these when resolving record types.
llvm-svn: 346511
The original commit was actually 2 unrelated bug fixes, but it turns
out the second bug fix wasn't quite correct, so the entire patch was
reverted. Resubmitting this half of the patch by itself, then will
follow up with a new patch which fixes the rest of the issue in a
more appropriate way.
llvm-svn: 346505
A previous commit fixed an issue with our AST generation where
we were outputting enum decls incorrectly. But we forgot to
update the test output. This patch updates the test output
accordingly.
llvm-svn: 346459
There are two bugs here. The first is that MSVC and clang-cl
emit their bss section under the name '.data' instead of '.bss'
but with the size and file offset set to 0. ObjectFilePECOFF
didn't handle this, and would only recognize a section as bss
if it was actually called '.bss'. The effect of this is that
if we tried to print the value of a variable that lived in BSS
we would fail.
The second bug is that ValueObjectVariable was only returning
the forward type, which is insufficient to print the value of an
enum. So we bump this up to the layout type.
Differential Revision: https://reviews.llvm.org/D54241
llvm-svn: 346430
In order to accurately put a type into the correct location in the AST
we construct from debug info, we need to be able to determine what
DeclContext (namespace, global, nested class, etc) that it goes into.
PDB doesn't contain this mapping. It does, however, contain the reverse
mapping. That is, for a given class type T, you can determine all
classes Q1, Q2, ..., Qn that are nested inside of T. We need to know,
for a given class type Q, what type T is it nested inside of.
This patch builds this map as a pre-processing step when we first
load the PDB by scanning every type. Initial tests show that while
this can be slow in debug builds of LLDB, it is quite fast in release
builds (less than 2 seconds for a ~1GB PDB, and it only needs to happen
once).
Furthermore, having this pre-processing step in place allows us to
repurpose it for building up other kinds of indexing to it down the
line. For the time being, this gives us very accurate reconstruction
of the DeclContext hierarchy.
Differential Revision: https://reviews.llvm.org/D54216
llvm-svn: 346429
This patch introduces the simple MSVCUndecoratedNameParser. It is needed for
parsing names of PDB symbols corresponding to template instantiations. For
example, for the name `operator<<A>'::`2'::B::operator> we can't just split the
name with :: (as it is implemented for now) to retrieve its scopes. This parser
processes such names in a more correct way.
Differential Revision: https://reviews.llvm.org/D52461
llvm-svn: 346213
A year or so ago, I re-wrote most of the lit infrastructure in LLVM so
that it wasn't so boilerplate-y. I added lots of common helper type
stuff, simplifed usage patterns, and made the code more elegant and
maintainable.
We migrated to this in LLVM, clang, and lld's lit files, but not in
LLDBs. This started to bite me recently, as the 4 most recent times I
tried to run the lit test suite in LLDB on a fresh checkout the first
thing that would happen is that python would just start crashing with
unhelpful backtraces and I would have to spend time investigating.
You can reproduce this today by doing a fresh cmake generation, doing
ninja lldb and then python bin/llvm-lit.py -sv ~/lldb/lit/SymbolFile at
which point you'll get a segfault that tells you nothing about what your
problem is.
I started trying to fix the issues with bandaids, but it became clear
that the proper solution was to just bring in the work I did in the rest
of the projects. The side benefit of this is that the lit configuration
files become much cleaner and more understandable as a result.
Differential Revision: https://reviews.llvm.org/D54009
llvm-svn: 346008
Summary:
This patch fixes the NativePDB tests to make them work from x86 command line too
Reviewers: zturner, stella.stamenova
Subscribers: aleksandr.urakov, teemperor, lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D54031
llvm-svn: 345974
This adds basic support for getting function signature types
into LLDB's type system, including into clang's AST. There are
a few edge cases which are not correctly handled, mostly dealing
with nested classes, but this isn't specific to functions and
apply equally to variable types. Note that no attempt has been
made yet to deal with member function types, which will happen
in subsequent patches.
Differential Revision: https://reviews.llvm.org/D53951
llvm-svn: 345848
Previous patches added support for dumping global variables of
primitive types, so we now do the same for class types.
For the most part, everything just worked, there was only one
minor bug needing fixed, which was that for variables of modified
types (e.g. const, volatile, etc) we can't resolve the forward
decl in CreateAndCacheType because the PdbSymUid must point to the
LF_MODIFIER which must point to the forward decl. So when it comes
time to call CompleteType, an assert was firing because we expected
to get a class, struct, union, or enum, but we were getting an
LF_MODIFIER instead.
The other issue is that one the newly added tests is for an array
member, which was not yet supported, so we add support for that
now in this patch.
There's probably room for other interesting layout test cases
here, but this at least should test the basics.
Differential Revision: https://reviews.llvm.org/D53822
llvm-svn: 345629
LLDB has the ability to display global variables, even without a running
process, via the target variable command. This is because global
variables are linker initialized, so their values are embedded directly
into the executables. This gives us great power for testing native PDB
functionality in a cross-platform manner, because we don't actually need
a running process. We can just create a target using an EXE file, and
display global variables. And global variables can have arbitrarily
complex types, so in theory we can fully exercise the type system,
record layout, and data formatters for native PDB files and PE/COFF
executables on any host platform, as long as our type does not require a
dynamic initializer.
This patch adds basic support for finding variables by name, and adds an
exhaustive test for fundamental data types and pointers / references to
fundamental data types.
Subsequent patches will extend this to typedefs, classes, pointers to
functions, and other cases.
Differential Revision: https://reviews.llvm.org/D53731
llvm-svn: 345373
This adds support to LLDB for named types (class, struct, union, and
enum). This is true cross platform support, and hits the PDB file
directly without a dependency on Windows. Tests are added which
compile a program with certain interesting types and then use
load the target in LLDB and use "type lookup -- <TypeName>" to
dump the layout of the type in LLDB without a running process.
Currently only fields are parsed -- we do not parse methods. Also
we don't deal with bitfields or virtual bases correctly. Those
will make good followups.
Differential Revision: https://reviews.llvm.org/D53511
llvm-svn: 345047
This adds -- before any filenames, so that /U doesn't get interpreted
as a command line.
It also adds better error checking, so that we don't get assertions
on the failure path when a file fails to parse as a PDB.
llvm-svn: 344429
