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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328348 91177308-0d34-0410-b5e6-96231b3b80d8
It previously only worked when the key and value types were
both 4 byte integers. We now have a use case for a non trivial
value type, so we need to extend it to support arbitrary value
types, which means templatizing it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327647 91177308-0d34-0410-b5e6-96231b3b80d8
This was originally reported as a bug with the symptom being "cvdump
crashes when printing an LLD-linked PDB that has an S_FILESTATIC record
in it". After some additional investigation, I determined that this was
a symptom of a larger problem, and in fact the real problem was in the
way we emitted the global PDB string table. As evidence of this, you can
take any lld-generated PDB, run cvdump -stringtable on it, and it would
return no results.
My hypothesis was that cvdump could not *find* the string table to begin
with. Normally it would do this by looking in the "named stream map",
finding the string /names, and using its value as the stream index. If
this lookup fails, then cvdump would fail to load the string table.
To test this hypothesis, I looked at the name stream map generated by a
link.exe PDB, and I emitted exactly those bytes into an LLD-generated
PDB. Suddenly, cvdump could read our string table!
This code has always been hacky and we knew there was something we
didn't understand. After all, there were some comments to the effect of
"we have to emit strings in a specific order, otherwise things don't
work". The key to fixing this was finally understanding this.
The way it works is that it makes use of a generic serializable hash map
that maps integers to other integers. In this case, the "key" is the
offset into a buffer, and the value is the stream number. If you index
into the buffer at the offset specified by a given key, you find the
name. The underlying cause of all these problems is that we were using
the identity function for the hash. i.e. if a string's offset in the
buffer was 12, the hash value was 12. Instead, we need to hash the
string *at that offset*. There is an additional catch, in that we have
to compute the hash as a uint32 and then truncate it to uint16.
Making this work is a little bit annoying, because we use the same hash
table in other places as well, and normally just using the identity
function for the hash function is actually what's desired. I'm not
totally happy with the template goo I came up with, but it works in any
case.
The reason we never found this bug through our own testing is because we
were building a /parallel/ hash table (in the form of an
llvm::StringMap<>) and doing all of our lookups and "real" hash table
work against that. I deleted all of that code and now everything goes
through the real hash table. Then, to test it, I added a unit test which
adds 7 strings and queries the associated values. I test every possible
insertion order permutation of these 7 strings, to verify that it really
does work as expected.
Differential Revision: https://reviews.llvm.org/D43326
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325386 91177308-0d34-0410-b5e6-96231b3b80d8
1) Don't write a /src/headerblock stream. This appears to be
written conditionally by MSVC, but it's not clear what the
condition is. For now, just remove it since we dont' know
what it is anyway and the particular pdb we've checked in
for the test doesn't have one.
2) Write a valid timestamp for the PDB file signature. This
leads to non-reproducible builds, but it matches the default
behavior of link, so it should be out default as well. If
we need reproducibility, we should add a separate command
line option for it that is off by default.
3) Write an empty FPO stream. MSVC seems to always write an
FPO stream. This change makes the stream directory match
up, although we still need to make the contents of the FPO
stream match.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307436 91177308-0d34-0410-b5e6-96231b3b80d8
If you dump a pdb to yaml, and then round-trip it back to a pdb,
and run cvdump -l <file> on the new pdb, cvdump will generate
output such as this.
*** LINES
** Module: "d:\src\llvm\test\DebugInfo\PDB\Inputs\empty.obj"
Error: Line number corrupted: invalid file id 0
<Unknown> (MD5), 0001:00000010-0000001A, line/addr pairs = 3
5 00000010 6 00000013 7 00000018
Note the error message about the corrupted line number.
It turns out that the problem is that cvdump cannot find the
/names stream (e.g. the global string table), and the reason it
can't find the /names stream is because it doesn't understand
the NameMap that we serialize which tells pdb consumers which
stream has the string table.
Some experimentation shows that if we add items to the hash
table in a specific order before serializing it, cvdump can read
it. This suggests that either we're using the wrong hash function,
or we're serializing something incorrectly, but it will take some
deeper investigation to figure out how / why. For now, this at
least allows cvdump to read our line information (and incidentally,
produces an identical byte sequence to what Microsoft tools
produce when writing the named stream map).
Differential Revision: https://reviews.llvm.org/D34491
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306233 91177308-0d34-0410-b5e6-96231b3b80d8
In doing so I discovered that we completely ignore some bytes
of the PDB Stream after we "finish" loading it. These bytes
seem to specify some additional information about what kind
of data is present in the PDB. A subsequent patch will add
code to read in those fields and store their values.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297983 91177308-0d34-0410-b5e6-96231b3b80d8
Before the endianness was specified on each call to read
or write of the StreamReader / StreamWriter, but in practice
it's extremely rare for streams to have data encoded in
multiple different endiannesses, so we should optimize for the
99% use case.
This makes the code cleaner and more general, but otherwise
has NFC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296415 91177308-0d34-0410-b5e6-96231b3b80d8
This was reverted because it was breaking some builds, and
because of incorrect error code usage. Since the CL was
large and contained many different things, I'm resubmitting
it in pieces.
This portion is NFC, and consists of:
1) Renaming classes to follow a consistent naming convention.
2) Fixing the const-ness of the interface methods.
3) Adding detailed doxygen comments.
4) Fixing a few instances of passing `const BinaryStream& X`. These
are now passed as `BinaryStreamRef X`.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296394 91177308-0d34-0410-b5e6-96231b3b80d8
r296215, "[PDB] General improvements to Stream library."
r296217, "Disable BinaryStreamTest.StreamReaderObject temporarily."
r296220, "Re-enable BinaryStreamTest.StreamReaderObject."
r296244, "[PDB] Disable some tests that are breaking bots."
r296249, "Add static_cast to silence -Wc++11-narrowing."
std::errc::no_buffer_space should be used for OS-oriented errors for socket transmission.
(Seek discussions around llvm/xray.)
I could substitute s/no_buffer_space/others/g, but I revert whole them ATM.
Could we define and use LLVM errors there?
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296258 91177308-0d34-0410-b5e6-96231b3b80d8
This adds various new functionality and cleanup surrounding the
use of the Stream library. Major changes include:
* Renaming of all classes for more consistency / meaningfulness
* Addition of some new methods for reading multiple values at once.
* Full suite of unit tests for reader / writer functionality.
* Full set of doxygen comments for all classes.
* Streams now store their own endianness.
* Fixed some bugs in a few of the classes that were discovered
by the unit tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296215 91177308-0d34-0410-b5e6-96231b3b80d8
This is part of a larger effort to get the Stream code moved
up to Support. I don't want to do it in one large patch, in
part because the changes are so big that it will treat everything
as file deletions and add, losing history in the process.
Aside from that though, it's just a good idea in general to
make small changes.
So this change only changes the names of the Stream related
source files, and applies necessary source fix ups.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296211 91177308-0d34-0410-b5e6-96231b3b80d8
In an effort to generalize this so it can be used by more than
just PDB code, we shouldn't assume little endian.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295525 91177308-0d34-0410-b5e6-96231b3b80d8
