Previously, our algorithm to compute a build id involved hashing the
executable and storing that as the GUID in the CV Debug Record chunk,
and setting the age to 1.
This breaks down in one very obvious case: a user adds some newlines to
a file, rebuilds, but changes nothing else. This causes new line
information and new file checksums to get written to the PDB, meaning
that the debug info is different, but the generated code would be the
same, so we would write the same build over again with an age of 1.
Anyone using a symbol cache would have a problem now, because the
debugger would open the executable, look at the age and guid, find a
matching PDB in the symbol cache and then load it. It would never copy
the new PDB to the symbol cache.
This patch implements the canonical Windows algorithm for updating
a build id, which is to check the existing executable first, and
re-use an existing GUID while bumping the age if it already
exists.
Differential Revision: https://reviews.llvm.org/D36758
llvm-svn: 310961
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.
llvm-svn: 307436
This is to reflect the evolving nature of the tool as being
useful for more than just dumping PDBs, as it can do many other
things.
Differential Revision: https://reviews.llvm.org/D34062
llvm-svn: 305106
When /DEBUG is not specified, /PDB should be ignored. When
/DEBUG is specified, a PDB should be output regardless of
whether or not /PDB is specified. /PDB just overrides the
default name.
This patch implements this behavior, and adds some tests, while
also removing a dead option /DEBUGPDB which was unused in any
code.
Differential Revision: https://reviews.llvm.org/D33302
llvm-svn: 303352
If `/debugtypes` is used to omit the codeview information, we would not
have constructed the debug info codeview record which is used to tie the
PDB to the binary. In such a case, rub out the GUID and Age fields.
llvm-svn: 294279
Fangrui Song