[lld] r344269 - Better support for POSIX paths in PDBs.

[Zachary Turner via llvm-commits]

Author: zturner
Date: Thu Oct 11 11:01:55 2018
New Revision: 344269

URL: http://llvm.org/viewvc/llvm-project?rev=344269&view=rev
Log:
Better support for POSIX paths in PDBs.

While it doesn't make a *ton* of sense for POSIX paths to be
in PDBs, it's possible to occur in real scenarios involving
cross compilation.

The tools need to be able to handle this, because certain types
of debugging scenarios are possible without a running process
and so don't necessarily require you to be on a Windows system.
These include post-mortem debugging and binary forensics (e.g.
using a debugger to disassemble functions and examine symbols
without running the process).

There's changes in clang, LLD, and lldb in this patch.  After
this the cross-platform disassembly and source-list tests pass
on Linux.

Furthermore, the behavior of LLD can now be summarized by a much
simpler rule than before: Unless you specify /pdbsourcepath and
/pdbaltpath, the PDB ends up with paths that are valid within
the context of the machine that the link is performed on.

Differential Revision: https://reviews.llvm.org/D53149

Modified:
    lld/trunk/COFF/PDB.cpp

Modified: lld/trunk/COFF/PDB.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/PDB.cpp?rev=344269&r1=344268&r2=344269&view=diff
==============================================================================
--- lld/trunk/COFF/PDB.cpp (original)
+++ lld/trunk/COFF/PDB.cpp Thu Oct 11 11:01:55 2018
@@ -222,26 +222,22 @@ public:
 // PDB to work without additional configuration:
 // https://docs.microsoft.com/en-us/visualstudio/debugger/debug-source-files-common-properties-solution-property-pages-dialog-box
 static void pdbMakeAbsolute(SmallVectorImpl<char> &FileName) {
-  if (sys::path::is_absolute(FileName, sys::path::Style::windows))
+  // The default behavior is to produce paths that are valid within the context
+  // of the machine that you perform the link on.  If the linker is running on
+  // a POSIX system, we will output absolute POSIX paths.  If the linker is
+  // running on a Windows system, we will output absolute Windows paths.  If the
+  // user desires any other kind of behavior, they should explicitly pass
+  // /pdbsourcepath and/or /pdbaltpath.
+  if (sys::path::is_absolute(FileName))
     return;
   if (Config->PDBSourcePath.empty()) {
-    // Debuggers generally want that PDB files contain absolute, Windows-style
-    // paths. On POSIX hosts, this here will produce an absolute POSIX-style
-    // path, which is weird -- but it's not clear what else to do.
-    // People doing cross builds should probably just always pass
-    // /pbdsourcepath: and make sure paths to input obj files and to lld-link
-    // itself are relative.
     sys::fs::make_absolute(FileName);
     return;
   }
-  // Using /pdbsourcepath: with absolute POSIX paths will prepend
-  // PDBSourcePath to the absolute POSIX path. Since absolute POSIX paths
-  // don't make sense in PDB files anyways, this is gargabe-in-garbage-out.
   SmallString<128> AbsoluteFileName = Config->PDBSourcePath;
-  sys::path::append(AbsoluteFileName, sys::path::Style::windows, FileName);
-  sys::path::native(AbsoluteFileName, sys::path::Style::windows);
-  sys::path::remove_dots(AbsoluteFileName, /*remove_dot_dots=*/true,
-                         sys::path::Style::windows);
+  sys::path::append(AbsoluteFileName, FileName);
+  sys::path::native(AbsoluteFileName);
+  sys::path::remove_dots(AbsoluteFileName, /*remove_dot_dots=*/true);
   FileName = std::move(AbsoluteFileName);
 }
 
@@ -444,8 +440,7 @@ PDBLinker::maybeMergeTypeServerPDB(ObjFi
         StringRef LocalPath =
             !File->ParentName.empty() ? File->ParentName : File->getName();
         SmallString<128> Path = sys::path::parent_path(LocalPath);
-        sys::path::append(
-            Path, sys::path::filename(TSPath, sys::path::Style::windows));
+        sys::path::append(Path, sys::path::filename(TSPath));
         return tryToLoadPDB(TSId, Path);
       },
       [&](std::unique_ptr<ECError> EC) -> Error {
@@ -1027,7 +1022,7 @@ void PDBLinker::addObjFile(ObjFile *File
   bool InArchive = !File->ParentName.empty();
   SmallString<128> Path = InArchive ? File->ParentName : File->getName();
   pdbMakeAbsolute(Path);
-  sys::path::native(Path, sys::path::Style::windows);
+  sys::path::native(Path);
   StringRef Name = InArchive ? File->getName() : StringRef(Path);
 
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
@@ -1312,7 +1307,7 @@ void PDBLinker::addSections(ArrayRef<Out
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
   NativePath = Config->PDBPath;
   pdbMakeAbsolute(NativePath);
-  sys::path::native(NativePath, sys::path::Style::windows);
+  sys::path::native(NativePath);
   uint32_t PdbFilePathNI = DbiBuilder.addECName(NativePath);
   auto &LinkerModule = ExitOnErr(DbiBuilder.addModuleInfo("* Linker *"));
   LinkerModule.setPdbFilePathNI(PdbFilePathNI);