Summary:
This considers module symbol streams and the global symbol stream to be
roots. Most types that this considers "unreferenced" are referenced by
LF_UDT_MOD_SRC_LINE id records, which VC seems to always include.
Essentially, they are types that the user can only find in the debugger
if they call them by name, they cannot be found by traversing a symbol.
In practice, around 80% of type information in a PDB is referenced by a
symbol. That seems like a reasonable number.
I don't really plan to do anything with this tool. It mostly just exists
for informational purposes, and to confirm that we probably don't need
to implement type reference tracking in LLD. We can continue to merge
all types as we do today without wasting space.
Reviewers: zturner, aganea
Subscribers: mgorny, hiraditya, arphaman, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59620
llvm-svn: 356692
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
The Globals table is a hash table keyed on symbol name, so
it's possible to lookup symbols by name in O(1) time. Add
a function to the globals stream to do this, and add an option
to llvm-pdbutil to exercise this, then use it to write some
tests to verify correctness.
llvm-svn: 343951
We didn't properly detect when a pointer was a member
pointer, and when that was the case we were not
properly returning class parent info. This caused
member pointers to render incorrectly in pretty mode.
However, we didn't even have pretty tests for pointers
in native mode, so those are also added now to ensure
this.
llvm-svn: 343393
Some records point to an LF_CLASS, LF_UNION, LF_STRUCTURE, or LF_ENUM
which is a forward reference and doesn't contain complete debug
information. In these cases, we'd like to be able to quickly locate the
full record. The TPI stream stores an array of pre-computed record hash
values, one for each type record. If we pre-process this on startup, we
can build a mapping from hash value -> {list of possible matching type
indices}. Since hashes of full records are only based on the name and or
unique name and not the full record contents, we can then use forward
ref record to compute the hash of what *would* be the full record by
just hashing the name, use this to get the list of possible matches, and
iterate those looking for a match on name or unique name.
llvm-pdbutil is updated to resolve forward references for the purposes
of testing (plus it's just useful).
Differential Revision: https://reviews.llvm.org/D52283
llvm-svn: 342656
The reference implementation uses a case-insensitive string
comparison for strings of equal length. This will cause the
string "tEo" to compare less than "VUo". However we were using
a case sensitive comparison, which would generate the opposite
outcome. Switch to a case insensitive comparison. Also, when
one of the strings contains non-ascii characters, fallback to
a straight memcmp.
The only way to really test this is with a DIA test. Before this
patch, the test will fail (but succeed if link.exe is used instead
of lld-link). After the patch, it succeeds even with lld-link.
llvm-svn: 336464
We add an option to dump the entire global / public symbol record
stream. Previously we would dump globals or publics, but not both.
And when we did dump them, we would always dump them in the order
they were referenced by the corresponding hash streams, not in
the order they were serialized in. This patch adds a lower level
mode that just dumps the whole stream in serialization order.
Additionally, when dumping global-extras, we now dump the hash
bitmap as well as the record offset instead of dumping all zeros
for the offsets.
llvm-svn: 336407
Using this, you can use llvm-pdbutil to export the contents of a
stream to a binary file, then run explain on the binary file so
that it treats the offset as an offset into the stream instead
of an offset into a file. This makes it easy to compare the
contents of the same stream from two different files.
llvm-svn: 329207
This command can dump the binary contents of a stream to a file.
This is useful when you want to do side-by-side comparisons of
a specific stream from two PDBs to examine the differences between
them. You can export both of them to a file, then open them up
side by side in a hex editor (for example), so as to eliminate any
differences that might arise from the contents being on different
blocks in the PDB.
In subsequent patches I plan to improve the "explain" subcommand
so that you can explain the contents of a binary file that isn't
necessarily a full PDB, but one of these dumped streams, by telling
the subcommand how to interpret the contents.
llvm-svn: 329002
This will show more detail when using `llvm-pdbutil explain` on an
offset in the DBI or PDB streams. Specifically, it will dig into
individual header fields and substreams to give a more precise
description of what the byte represents.
llvm-svn: 328878
When investigating various things, we often have a file offset
and what to know what's in the PDB at that address. For example
we may be doing a binary comparison of two LLD-generated PDBs
to look for sources of non-determinism, or we may wish to compare
an LLD-generated PDB with a Microsoft generated PDB for sources
of byte-for-byte incompatibility. In these cases, we can do a
binary diff of the two files, and once we find a mismatched byte
we can use explain to figure out what that byte is, immediately
honining in on the problem.
This patch implements this by trying to narrow the meaning of
a particular file offset down as much as possible.
Differential Revision: https://reviews.llvm.org/D44959
llvm-svn: 328799
This has been made obsolete by the fact that almost all of the
things it previously checked for are no longer relevant since
we can just compare bytes in a lot of places.
llvm-svn: 328562
When investigating bugs in PDB generation, the first step is
often to do the same link with link.exe and then compare PDBs.
But comparing PDBs is hard because two completely different byte
sequences can both be correct, so it hampers the investigation when
you also have to spend time figuring out not just which bytes are
different, but also if the difference is meaningful.
This patch fixes a couple of cases related to string table emission,
hash table emission, and the order in which we emit strings that
makes more of our bytes the same as the bytes generated by MS PDBs.
Differential Revision: https://reviews.llvm.org/D44810
llvm-svn: 328348
This is still failing on a different bot this time due to some
issue related to hashing absolute paths. Reverting until I can
figure it out.
llvm-svn: 328014
The issue causing this to fail in certain configurations
should be fixed.
It was due to the fact that DIA apparently expects there to be
a null string at ID 1 in the string table. I'm not sure why this
is important but it seems to make a difference, so set it.
llvm-svn: 328002
Natvis is a debug language supported by Visual Studio for
specifying custom visualizers. The /NATVIS option is an
undocumented link.exe flag which will take a .natvis file
and "inject" it into the PDB. This way, you can ship the
debug visualizers for a program along with the PDB, which
is very useful for postmortem debugging.
This is implemented by adding a new "named stream" to the
PDB with a special name of /src/files/<natvis file name>
and simply copying the contents of the xml into this file.
Additionally, we need to emit a single stream named
/src/headerblock which contains a hash table of embedded
files to records describing them.
This patch adds this functionality, including the /NATVIS
option to lld-link.
Differential Revision: https://reviews.llvm.org/D44328
llvm-svn: 327895
We have llvm-readobj for dumping CodeView from object files, and
llvm-pdbutil has always been more focused on PDB. However,
llvm-pdbutil has a lot of useful options for summarizing debug
information in aggregate and presenting high level statistical
views. Furthermore, it's arguably better as a testing tool since
we don't have to write tests to conform to a state-machine like
structure where you match multiple lines in succession, each
depending on a previous match. llvm-pdbutil dumps much more
concisely, so it's possible to use single-line matches in many
cases where as with readobj tests you have to use multi-line
matches with an implicit state machine.
Because of this, I'm adding object file support to llvm-pdbutil.
In fact, this mirrors the cvdump tool from Microsoft, which also
supports both object files and pdb files. In the future we could
perhaps rename this tool llvm-cvutil.
In the meantime, this allows us to deep dive into object files
the same way we already can with PDB files.
llvm-svn: 312358
This adds a new command line option, -udt-stats, which breaks
down the stats of S_UDT records. These are one of the biggest
contributors to the size of /DEBUG:FASTLINK PDBs, so they need
some additional tools to be able to analyze their usage. This
option will dig into each S_UDT record and determine what kind
of record it points to, and then break down the statistics by
the target type. The goal here is to identify how our object
files differ from MSVC object files in S_UDT records, so that
we can output fewer of them and reach size parity.
llvm-svn: 312276
This adds support for dumping a summary of module symbols
and CodeView debug chunks. This option prints a table for
each module of all of the symbols that occurred in the module
and the number of times it occurred and total byte size. Then
at the end it prints the totals for the entire file.
Additionally, this patch adds the -jmc (just my code) option,
which suppresses modules which are from external libraries or
linker imports, so that you can focus only on the object files
and libraries that originate from your own source code.
llvm-svn: 311338
Image section headers are stored in the DBI stream, but we
had no way to dump them. This patch adds dumping support,
along with some tests that LLD actually dumps them correctly.
Differential Revision: https://reviews.llvm.org/D36332
llvm-svn: 310107
Often something interesting (like a symbol) is in a particular
module, and you don't want to dump symbols from all other 300
modules to see the one you want. This adds a -modi option so that
we only dump the specified module.
llvm-svn: 310000
Sometimes the normal module equivalence detection algorithm doesn't
quite work. For example, you might build the same program with
MSVC and clang-cl, outputting to different object files, exes, and
PDBs, then compare them. If the object files have different names
though, then they won't be treated as equivalent. This way we
can force specific module indices to be treated as equivalent.
llvm-svn: 309983
Recently problems have been discovered in the way we write the FPM
(free page map). In order to fix this, we first need to establish
a baseline about what a correct FPM looks like using an MSVC
generated PDB, so that we can then make our own generated PDBs
match. And in order to do this, the dumper needs a mode where it
can dump an FPM so that we can write tests for it.
This patch adds a command to dump the FPM, as well as a test against
a known-good PDB.
llvm-svn: 309894
The PDB "symbol stream" actually contains symbol records for the publics
and the globals stream. The globals and publics streams are essentially
hash tables that point into a single stream of records. In order to
match cvdump's behavior, we need to only dump symbol records referenced
from the hash table. This patch implements that, and then implements
global stream dumping, since it's just a subset of public stream
dumping.
Now we shouldn't see S_PROCREF or S_GDATA32 records when dumping
publics, and instead we should see those record in the globals stream.
llvm-svn: 309066
This includes the hash table, the address map, and the thunk table and
section offset table. The last two are only used for incremental
linking, which LLD doesn't support, so they are less interesting. The
hash table is particularly important to get right, since this is the one
of the streams that debuggers use to translate addresses to symbols.
llvm-svn: 308764
This was originally reverted because of two issues.
1) Printing ANSI color escape codes even when outputting to
a file
2) Module name comparisons were failing when comparing a PDB
generated on one machine to a PDB generated on another
machine.
I attempted to fix#2 by adding command line options which let
you specify prefixes to strip from the beginning of embedded
paths, which effectively lets us specify a path to "base" each
PDB from and only compare the parts under the base. But this is
tricky because PDB paths always use Windows path syntax, even
when they are created on non-Windows hosts. A problem still
existed when constructing the prefix to strip, where we were
accidentally using a host-specific path separator instead of
a Windows path separator.
This resubmission fixes the issue on Linux (and I have verified
that the test now passes on Linux).
llvm-svn: 307571
A test was checked in on Friday that worked by checking in an
object file and PDB generated locally by MSVC, and then having
the test run lld-link on the object file and diffing LLD's PDB
against the checked in PDB.
This failed because part of the diffing algorithm involves
determining if two modules are the same, and if so drilling into
the module and diffing individual fields of the module. The
only thing we can use to make this determination though is the
"name" of the module, which is a path to where the module (obj
file) was read from on the machine where it was linked. This
fails for obvious reasons when comparing a PDB generated on one
machine to a PDB on another machine.
The fix employed here is to add two command line options to the
diff subcommand, which allow the user to specify a "binary root
path". The bin root path, if specified, is stripped from the
beginning of any embedded PDB paths. The test is updated to
specify the user's local test output directory for the left
PDB, and is hardcoded to the location where the original PDB
was created for the right PDB. This way all the equivalence
comparisons should succeed.
llvm-svn: 307555
A couple of things were different about our generated PDBs.
1) We were outputting the wrong Version on the PDB Stream.
The version we were setting was newer than what MSVC is setting.
It's not clear what the implications are, but we change LLD
to use PdbImplVC70, as MSVC does.
2) For the optional debug stream indices in the DBI Stream, we
were outputting 0 to mean "the stream is not present". MSVC
outputs uint16_t(-1), which is the "correct" way to specify
that a stream is not present. So we fix that as well.
3) We were setting the PDB Stream signature to 0. This is supposed
to be the result of calling time(nullptr). Although this leads
to non-deterministic builds, a better way to solve that is by
having a command line option explicitly for generating a
reproducible build, and have the default behavior of lld-link
match the default behavior of link.
To test this, I'm making use of the new and improved `pdb diff`
sub command. To make it suitable for writing tests against, I had
to modify the diff subcommand slightly to print less verbose output.
Previously it would always print | <column> | <value1> | <value2> |
which is quite verbose, and the values are fragile. All we really
want to know is "did we produce the same value as link?" So I added
command line options to print a single character representing the
result status (different, identical, equivalent), and another to
hide the value display. Note that just inspecting the diff output
used to write the test, you can see some things that are obviously
wrong. That is just reflective of the fact that this is the state
of affairs today, not that we're asserting that this is "correct".
We can use this as a starting point to discover differences, fix
them, and update the test.
Differential Revision: https://reviews.llvm.org/D35086
llvm-svn: 307422
Previously we had the -type-index option which would dump the record of
a single, but we had no way to follow the dependency graph backwards and
also dump all dependent types.
Having this option makes test-writing better, because we can limit the
test to only those records that are of importance for the thing we're
trying to test, which allows us to use things like CHECK-NEXT to reduce
fragility.
Differential Revision: https://reviews.llvm.org/D34899
llvm-svn: 306852
This is useful when you want to look at a specific chunk of a
stream or look for discontinuities, and you need to know the
list of blocks occupied by a stream.
llvm-svn: 306150
This patch dumps the raw bytes of the pdb name map which contains
the mapping of stream name to stream index for the string table
and other reserved streams.
llvm-svn: 306148
Normally we can only make sense of the content of a PDB in terms
of streams and blocks, but in some cases it may be useful to dump
bytes at a specific absolute file offset. For example, if you
know that some interesting data is at a particular location and
you want to see some surrounding data.
llvm-svn: 306146
This idea originally came about when I was doing some deep
investigation of why certain bytes in a PDB that we round-tripped
differed from their original bytes in the source PDB. I found
myself having to hack up the code in many places to dump the
bytes of this substream, or that record. It would be nice if
we could just do this for every possible stream, substream,
debug chunk type, etc.
It doesn't make sense to put this under dump because there's just
so many options that would detract from the more common use case
of just dumping deserialized records. So making a new subcommand
seems like the most logical course of action. In doing so, we
already have two command line options that are suitable for this
new subcommand, so start out by moving them there.
llvm-svn: 306056
Now you run llvm-pdbutil dump <options>. This is a followup
after having renamed the tool, whereas before raw was obviously
just the style of dumping, whereas now "dump" is the action to
perform with the "util".
llvm-svn: 306055
Alexandre Ganea