[PDB] Fix bug when using multiple PCH header objects with the same name.

A common pattern in Windows is to have all your precompiled headers
use an object named stdafx.obj.  If you've got a project with many
different static libs, you might use a separate PCH for each one of
these.

During the final link step, a file from A might reference the PCH
object from A, but it will have the same name (stdafx.obj) as any
other PCH from another project.  The only difference will be the
path.  For example, A might be A/stdafx.obj while B is B/stdafx.obj.

The existing algorithm checks only the filename that was passed on
the command line (or stored in archive), but this is insufficient in
the case where relative paths are used, because depending on the
command line object file / library order, it might find the wrong
PCH object first resulting in a signature mismatch.

The fix here is to simply check whether the absolute path of the
PCH object (which is stored in the input obj file for the file that
references the PCH) *ends with* the full relative path of whatever
is specified on the command line (or is in the archive).

Differential Revision: https://reviews.llvm.org/D66431

llvm-svn: 374442

lld/COFF/PDB.cpp

@@ -514,16 +514,15 @@ static bool equals_path(StringRef path1, StringRef path2) {
   return path1.equals(path2);
 #endif
 }
-
 // Find by name an OBJ provided on the command line
-static ObjFile *findObjByName(StringRef fileNameOnly) {
-  SmallString<128> currentPath;
-
+static ObjFile *findObjWithPrecompSignature(StringRef fileNameOnly,
+                                            uint32_t precompSignature) {
   for (ObjFile *f : ObjFile::instances) {
     StringRef currentFileName = sys::path::filename(f->getName());
 
-    // Compare based solely on the file name (link.exe behavior)
-    if (equals_path(currentFileName, fileNameOnly))
+    if (f->pchSignature.hasValue() &&
+        f->pchSignature.getValue() == precompSignature &&
+        equals_path(fileNameOnly, currentFileName))
       return f;
   }
   return nullptr;
@@ -560,22 +559,15 @@ Expected<const CVIndexMap &> PDBLinker::aquirePrecompObj(ObjFile *file) {
 
   // link.exe requires that a precompiled headers object must always be provided
   // on the command-line, even if that's not necessary.
-  auto precompFile = findObjByName(precompFileName);
+  auto precompFile =
+      findObjWithPrecompSignature(precompFileName, precomp.Signature);
   if (!precompFile)
     return createFileError(
-        precompFileName.str(),
-        make_error<pdb::PDBError>(pdb::pdb_error_code::external_cmdline_ref));
+        precomp.getPrecompFilePath().str(),
+        make_error<pdb::PDBError>(pdb::pdb_error_code::no_matching_pch));
 
   addObjFile(precompFile, &indexMap);
 
-  if (!precompFile->pchSignature)
-    fatal(precompFile->getName() + " is not a precompiled headers object");
-
-  if (precomp.getSignature() != precompFile->pchSignature.getValueOr(0))
-    return createFileError(
-        precomp.getPrecompFilePath().str(),
-        make_error<pdb::PDBError>(pdb::pdb_error_code::signature_out_of_date));
-
   return indexMap;
 }
 

lld/test/COFF/precomp-link-samename.test

@@ -0,0 +1,36 @@
+RUN: lld-link %S/Inputs/precompb/useprecomp.obj %S/Inputs/precompa/precomp.obj %S/Inputs/precompb/precomp.obj \
+RUN:     %S/Inputs/precompa/useprecomp.obj /nodefaultlib /entry:main /debug /pdb:%t.pdb /out:%t.exe  \
+RUN:     /summary | FileCheck %s -check-prefix SUMMARY
+
+RUN: llvm-pdbutil dump -types %t.pdb | FileCheck %s
+
+
+CHECK: Types (TPI Stream)
+CHECK-NOT: LF_PRECOMP
+CHECK-NOT: LF_ENDPRECOMP
+
+
+SUMMARY:                                     Summary
+SUMMARY-NEXT: --------------------------------------------------------------------------------
+SUMMARY-NEXT:               4 Input OBJ files (expanded from all cmd-line inputs)
+SUMMARY-NEXT:               0 PDB type server dependencies
+SUMMARY-NEXT:               2 Precomp OBJ dependencies
+
+// precompa/precomp.cpp
+#include "precomp.h"
+
+// precompa/useprecomp.cpp
+#include "precomp.h"
+int main(int argc, char **argv) { return 0; }
+
+// precompa/precomp.h
+int precompa_symbol = 42;
+
+// precompb/precomp.cpp
+#include "precomp.h"
+
+// precompb/useprecomp.cpp
+#include "precomp.h"
+
+// precompb/precomp.h
+int precompb_symbol = 142;

lld/test/COFF/precomp-link.test

@@ -9,10 +9,10 @@ RUN: lld-link %S/Inputs/precomp-a.obj %S/Inputs/precomp-invalid.obj %S/Inputs/pr
 RUN: not lld-link %S/Inputs/precomp-a.obj %S/Inputs/precomp-b.obj /nodefaultlib /entry:main /debug /pdb:%t.pdb /out:%t.exe /opt:ref /opt:icf 2>&1 | FileCheck %s -check-prefix FAILURE-MISSING-PRECOMPOBJ
 
 FAILURE: warning: Cannot use debug info for '{{.*}}precomp-invalid.obj' [LNK4099]
-FAILURE-NEXT: failed to load reference '{{.*}}precomp.obj': The signature does not match; the file(s) might be out of date.
+FAILURE-NEXT: failed to load reference '{{.*}}precomp.obj': No matching precompiled header could be located.
 
 FAILURE-MISSING-PRECOMPOBJ: warning: Cannot use debug info for '{{.*}}precomp-a.obj' [LNK4099]
-FAILURE-MISSING-PRECOMPOBJ-NEXT: failed to load reference '{{.*}}precomp.obj': The path to this file must be provided on the command-line
+FAILURE-MISSING-PRECOMPOBJ-NEXT: failed to load reference '{{.*}}precomp.obj': No matching precompiled header could be located.
 
 CHECK: Types (TPI Stream)
 CHECK-NOT: LF_PRECOMP

llvm/include/llvm/DebugInfo/PDB/GenericError.h

@@ -20,7 +20,7 @@ enum class pdb_error_code {
   dia_sdk_not_present,
   dia_failed_loading,
   signature_out_of_date,
-  external_cmdline_ref,
+  no_matching_pch,
   unspecified,
 };
 } // namespace pdb

llvm/lib/DebugInfo/PDB/GenericError.cpp

@@ -34,8 +34,8 @@ class PDBErrorCategory : public std::error_category {
       return "The PDB file path is an invalid UTF8 sequence.";
     case pdb_error_code::signature_out_of_date:
       return "The signature does not match; the file(s) might be out of date.";
-    case pdb_error_code::external_cmdline_ref:
-      return "The path to this file must be provided on the command-line.";
+    case pdb_error_code::no_matching_pch:
+      return "No matching precompiled header could be located.";
     }
     llvm_unreachable("Unrecognized generic_error_code");
   }