[llvm-pdbutil] Improve diff mode.

We're getting to the point that some MS tools (e.g. DIA) can recognize
our PDBs but others (e.g. link.exe) cannot. I think the way forward is
to improve our tooling to help us find differences more easily. For
example, if we can compile the same program with clang-cl and cl and
have a tool tell us all the places where the PDBs differ, this could
tell us what we're doing wrong. It's tricky though, because there are a
lot of "benign" differences in a PDB. For example, if the string table
in one PDB consists of "foo" followed by "bar" and in the other PDB it
consists of "bar" followed by "foo", this is not necessarily a critical
difference, as long as the uses of these strings also refer to the
correct location. On the other hand, if the second PDB doesn't even
contain the string "foo" at all, this is a critical difference.

diff mode has been in llvm-pdbutil for quite a while, but because of the
above challenge along with some others, it's been hard to make it
useful. I think this patch addresses that. It looks for all the same
things, but it now prints the output in tabular format (carefully
formatted and aligned into tables and fields), and it highlights
critical differences in red, non-critical differences in yellow, and
identical fields in green.  This makes it easy to spot the places we
differ, and the general concept of outputting arbitrary fields in
tabular format can be extended to provide analysis into many of the
different types of information that show up in a PDB.

Differential Revision: https://reviews.llvm.org/D35039

llvm-svn: 307421

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/tools/llvm-pdbutil/FormatUtil.h b/llvm/tools/llvm-pdbutil/FormatUtil.h
index 31e4be34958..df32ed9360f 100644
--- a/llvm/tools/llvm-pdbutil/FormatUtil.h
+++ b/llvm/tools/llvm-pdbutil/FormatUtil.h
@@ -23,6 +23,7 @@ namespace llvm {
 namespace pdb {
 
 std::string truncateStringBack(StringRef S, uint32_t MaxLen);
+std::string truncateStringMiddle(StringRef S, uint32_t MaxLen);
 std::string truncateStringFront(StringRef S, uint32_t MaxLen);
 std::string truncateQuotedNameFront(StringRef Label, StringRef Name,
                                     uint32_t MaxLen);