Merge pull request #4785 from tmat/PdbPadding

PDB path padding

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs

@@ -6232,7 +6232,7 @@ class Program3
 
             using (var peFile = File.OpenRead(exe.Path))
             {
-                PdbValidation.ValidateDebugDirectory(peFile, pdb.Path, isPortable: false);
+                PdbValidation.ValidateDebugDirectory(peFile, pdb.Path, isPortable: false, isDeterministic: false);
             }
 
             Assert.True(new FileInfo(exe.Path).Length < oldSize);
@@ -6243,7 +6243,7 @@ class Program3
 
             using (var peFile = File.OpenRead(exe.Path))
             {
-                PdbValidation.ValidateDebugDirectory(peFile, pdb.Path, isPortable: false);
+                PdbValidation.ValidateDebugDirectory(peFile, pdb.Path, isPortable: false, isDeterministic: false);
             }
         }
 

src/Compilers/Core/Portable/Compilation/Compilation.cs

@@ -1805,6 +1805,8 @@ private static EmitResult ToEmitResultAndFree(DiagnosticBag diagnostics, bool su
             return new EmitResult(success, diagnostics.ToReadOnlyAndFree());
         }
 
+        internal bool IsEmitDeterministic => this.Feature("deterministic")?.Equals("true", StringComparison.OrdinalIgnoreCase) ?? false;
+
         internal bool SerializeToPeStream(
             CommonPEModuleBuilder moduleBeingBuilt,
             EmitStreamProvider peStreamProvider,
@@ -1825,7 +1827,7 @@ private static EmitResult ToEmitResultAndFree(DiagnosticBag diagnostics, bool su
             Stream portablePdbTempStream = null;
             Stream peTempStream = null;
 
-            bool deterministic = this.Feature("deterministic")?.Equals("true", StringComparison.OrdinalIgnoreCase) ?? false;
+            bool deterministic = IsEmitDeterministic;
             bool emitPortablePdb = moduleBeingBuilt.EmitOptions.DebugInformationFormat == DebugInformationFormat.PortablePdb;
             string pdbPath = (pdbStreamProvider != null) ? (moduleBeingBuilt.EmitOptions.PdbFilePath ?? FileNameUtilities.ChangeExtension(SourceModule.Name, "pdb")) : null;
 

src/Compilers/Core/Portable/PEWriter/PeWriter.cs

@@ -27,6 +27,13 @@ internal sealed class PeWriter
         private const string ResourceSectionName = ".rsrc";
         private const string RelocationSectionName = ".reloc";
 
+        /// <summary>
+        /// Minimal size of PDB path in Debug Directory. We pad the path to this minimal size to
+        /// allow some tools to patch the path without the need to rewrite the entire image.
+        /// This is a workaround put in place until these tools are retired.
+        /// </summary>
+        private readonly int _minPdbPath;
+
         /// <summary>
         /// True if we should attempt to generate a deterministic output (no timestamps or random data).
         /// </summary>
@@ -53,6 +60,8 @@ internal sealed class PeWriter
             _pdbPathOpt = pdbPathOpt;
             _deterministic = deterministic;
 
+            // The PDB padding workaround is only needed for legacy tools that don't use deterministic build.
+            _minPdbPath = deterministic ? 0 : 260;
             _nativeResourcesOpt = nativeResourcesOpt;
             _nativeResourceSectionOpt = nativeResourceSectionOpt;
             _is32bit = !_properties.Requires64bits;
@@ -457,8 +466,7 @@ private int ComputeSizeOfDebugDirectoryData()
                 4 +              // 4B signature "RSDS"
                 16 +             // GUID
                 sizeof(uint) +   // Age
-                Encoding.UTF8.GetByteCount(_pdbPathOpt) +
-                1;               // Null terminator
+                Math.Max(BlobUtilities.GetUTF8ByteCount(_pdbPathOpt) + 1, _minPdbPath);
         }
 
         private int ComputeSizeOfDebugDirectory()
@@ -1380,9 +1388,13 @@ private void WriteDebugTable(Stream peStream, SectionHeader textSection, Content
             writer.WriteUInt32(PdbWriter.Age);
 
             // UTF-8 encoded zero-terminated path to PDB
+            int pathStart = writer.Position;
             writer.WriteUTF8(_pdbPathOpt, allowUnpairedSurrogates: true);
             writer.WriteByte(0);
 
+            // padding:
+            writer.WriteBytes(0, Math.Max(0, _minPdbPath - (writer.Position - pathStart)));
+
             writer.WriteContentTo(peStream);
             writer.Free();
         }

src/Test/Utilities/Portable/Pdb/PdbValidation.cs

@@ -226,13 +226,13 @@ private static void RemoveNonPortablePdb(XElement expectedNativePdb)
                     actual = PdbToXmlConverter.ToXml(pdbbits, exebits, options, methodName: qualifiedMethodName);
                 }
 
-                ValidateDebugDirectory(exebits, compilation.AssemblyName + ".pdb", portable);
+                ValidateDebugDirectory(exebits, compilation.AssemblyName + ".pdb", portable, compilation.IsEmitDeterministic);
             }
 
             return actual;
         }
 
-        public static void ValidateDebugDirectory(Stream peStream, string pdbPath, bool isPortable)
+        public static void ValidateDebugDirectory(Stream peStream, string pdbPath, bool isPortable, bool isDeterministic)
         {
             peStream.Seek(0, SeekOrigin.Begin);
             PEReader peReader = new PEReader(peStream);
@@ -281,11 +281,28 @@ public static void ValidateDebugDirectory(Stream peStream, string pdbPath, bool
 
             Assert.Equal(1u, reader.ReadUInt32());
 
-            byte[] pathBlob = new byte[sizeOfData - 24 - 1];
+            byte[] pathBlob = new byte[sizeOfData - 24];
             reader.Read(pathBlob, 0, pathBlob.Length);
-            var actualPath = Encoding.UTF8.GetString(pathBlob);
+
+            int terminator = Array.IndexOf(pathBlob, (byte)0);
+            Assert.True(terminator >= 0, "Path should be NUL terminated");
+
+            for (int i = terminator + 1; i < pathBlob.Length; i++)
+            {
+                Assert.Equal(0, pathBlob[i]);
+            }
+
+            if (isDeterministic)
+            {
+                Assert.Equal(pathBlob.Length - 1, terminator);
+            }
+            else
+            {
+                Assert.True(pathBlob.Length >= 260, "Path should be at least MAX_PATH long");
+            }
+
+            var actualPath = Encoding.UTF8.GetString(pathBlob, 0, terminator);
             Assert.Equal(pdbPath, actualPath);
-            Assert.Equal(0, reader.ReadByte());
         }
 
         public static void VerifyMetadataEqualModuloMvid(Stream peStream1, Stream peStream2)