Support long paths in CoreCLR runtime on Windows

The CoreCLR runtime is updated to support long file paths on Windows.
Pending updates to mscorlib.dll, the following scenarios are supported:
* Run managed apps from a long path.
* Load CoreCLR runtime and framework from a long path.
* Load user assemblies from a long path.
* Run CrossGen from a long path, with its input/output from a long path.
* Generate debug log file at a long path.

The following scenarios are not yet supported, and will be fixed in
future commits:
* Mscorlib.dll and framework assemblies are not yet long path compatible.
  Note that until mscorlib.dll is fixed, most of the runtime changes can't
  actually be used.
* Support on non-Windows platforms.
* Support for debugging and error reporting.
* Tools such as ilasm or ildasm.

3 files changed, 50 insertions, 18 deletions

diff --git a/src/vm/rtlfunctions.cpp b/src/vm/rtlfunctions.cpp
index 7883f678b4..b7cb78761a 100644
--- a/src/vm/rtlfunctions.cpp
+++ b/src/vm/rtlfunctions.cpp
@@ -76,26 +76,42 @@ VOID InstallEEFunctionTable (
     CONTRACTL_END;
 
     static LPWSTR wszModuleName = NULL;
-    static WCHAR  rgwModuleName[MAX_LONGPATH] = {0};
+    static WCHAR  rgwModuleName[MAX_LONGPATH] = { 0 };
 
     if (wszModuleName == NULL)        
     {
-        WCHAR rgwTempName[MAX_LONGPATH] = {0};
-        DWORD dwTempNameSize = MAX_LONGPATH;
+        StackSString ssTempName;
+        DWORD dwTempNameSize;
 
         // Leaves trailing backslash on path, producing something like "c:\windows\microsoft.net\framework\v4.0.x86dbg\"
-        HRESULT hr = GetInternalSystemDirectory(rgwTempName, &dwTempNameSize);
+        LPCWSTR pszSysDir = GetInternalSystemDirectory(&dwTempNameSize);
 
         //finish creating complete path and copy to buffer if we can
-        if (FAILED(hr) ||
-            (wcscat_s(rgwTempName, MAX_LONGPATH, MAIN_DAC_MODULE_DLL_NAME_W) != 0) ||
-            (wcscpy_s(rgwModuleName, MAX_LONGPATH, rgwTempName) != 0))
+        if (pszSysDir == NULL)
         {   // The CLR should become unavailable in this case.
             EEPOLICY_HANDLE_FATAL_ERROR(COR_E_EXECUTIONENGINE);
         }
 
-        // publish result
-        InterlockedExchangeT(&wszModuleName, rgwModuleName);
+        ssTempName.Set(pszSysDir);
+        ssTempName.Append(MAIN_DAC_MODULE_DLL_NAME_W);
+
+        if (ssTempName.GetCount() < MAX_LONGPATH)
+        {
+            wcscpy_s(rgwModuleName, MAX_LONGPATH, ssTempName.GetUnicode());
+
+            // publish result
+            InterlockedExchangeT(&wszModuleName, rgwModuleName);
+        }
+        else
+        {
+            NewArrayHolder<WCHAR> wzTempName(DuplicateStringThrowing(ssTempName.GetUnicode()));
+
+            // publish result
+            if (InterlockedCompareExchangeT(&wszModuleName, (LPWSTR)wzTempName, nullptr) == nullptr)
+            {
+                wzTempName.SuppressRelease();
+            }
+        }
     }
 
     if (!RtlInstallFunctionTableCallback(
diff --git a/src/vm/stdinterfaces.cpp b/src/vm/stdinterfaces.cpp
index 6ffbb4abea..c80ec3fe22 100644
--- a/src/vm/stdinterfaces.cpp
+++ b/src/vm/stdinterfaces.cpp
@@ -776,8 +776,21 @@ HRESULT GetITypeLibForAssembly(Assembly *pAssembly, ITypeLib **ppTLB, int bAutoC
 
     // Add a ".tlb" extension and try again.
     IfFailGo(rName.ReSizeNoThrow((int)(wcslen(szModule) + 5)));
-    SplitPath(szModule, rcDrive, _MAX_DRIVE, rcDir, _MAX_DIR, rcFname, _MAX_FNAME, 0, 0);
-    MakePath(rName.Ptr(), rcDrive, rcDir, rcFname, W(".tlb"));
+    // Check if szModule already has an extension.
+    LPCWSTR ext;
+    size_t extSize;
+    SplitPathInterior(szModule, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, &ext, &extSize);
+    if (ext != nullptr)
+    {
+        // szModule already has an extension. Make a copy without the extension.
+        wcsncpy_s(rName.Ptr(), rName.Size(), szModule, ext - szModule);
+    }
+    else
+    {
+        // szModule does not have an extension. Copy the whole string.
+        wcscpy_s(rName.Ptr(), rName.Size(), szModule);
+    }
+    wcscat_s(rName.Ptr(), rName.Size(), W(".tlb"));
     
     hr = LoadTypeLibExWithFlags(rName.Ptr(), flags, &pITLB);
     if(hr == S_OK)
diff --git a/src/vm/tlbexport.cpp b/src/vm/tlbexport.cpp
index 21f8b143a9..01f5239620 100644
--- a/src/vm/tlbexport.cpp
+++ b/src/vm/tlbexport.cpp
@@ -276,10 +276,13 @@ void ExportTypeLibFromLoadedAssembly(
 
     TypeLibExporter exporter;           // Exporter object.
     LPCWSTR     szModule=0;             // Module filename.
-    WCHAR       rcDrive[_MAX_DRIVE] = {0};
-    WCHAR       rcDir[_MAX_DIR] = {0};
-    WCHAR       rcFile[_MAX_FNAME] = {0};
-    WCHAR       rcTlb[_MAX_PATH+5] = {0};     // Buffer for the tlb filename.
+    StackSString ssDrive;
+    StackSString ssDir;
+    StackSString ssFile;
+    size_t      cchDrive;
+    size_t      cchDir;
+    size_t      cchFile;
+    CQuickWSTR  rcTlb;     // Buffer for the tlb filename.
     int         bDynamic=0;             // If true, dynamic module.
     Module      *pModule;               // The Assembly's SecurityModule.
     
@@ -310,9 +313,9 @@ void ExportTypeLibFromLoadedAssembly(
             szTlb = W("");
         else
         {
-            SplitPath(szModule, rcDrive, _MAX_DRIVE, rcDir, _MAX_DIR, rcFile, _MAX_FNAME, 0, 0);
-            MakePath(rcTlb, rcDrive, rcDir, rcFile, szTypeLibExt);
-            szTlb = rcTlb;
+            SplitPath(szModule, &ssDrive, &ssDir, &ssFile, nullptr);
+            MakePath(rcTlb, ssDrive.GetUnicode(), ssDir.GetUnicode(), ssFile.GetUnicode(), szTypeLibExt);
+            szTlb = rcTlb.Ptr();
         }
     }