lld-link: Reject more than one resource .obj file

Users are exepcted to pass all .res files to the linker, which then
merges all the resource in all .res files into a tree structure and then
converts the final tree structure to a .obj file with .rsrc$01 and
.rsrc$02 sections and then links that.

If the user instead passes several .obj files containing such resources,
the correct thing to do would be to have custom code to merge the trees
in the resource sections instead of doing normal section merging -- but
link.exe rejects if multiple resource obj files are passed in with
LNK4078, so let lld-link do that too instead of silently writing broken
.rsrc sections in that case.

The only real way to run into this is if users manually convert .res
files to .obj files by running cvtres and then handing the resulting
.obj files to lld-link instead, which in practice likely never happens.

(lld-link is slightly stricter than link.exe now: If link.exe is passed
one .obj file created by cvtres, and a .res file, for some reason it
just emits a warning instead of an error and outputs strange looking
data. lld-link now errors out on mixed input like this.)

One way users could accidentally run into this is the following
scenario: If a .res file is passed to lib.exe, then lib.exe calls
cvtres.exe on the .res file before putting it in the output .lib.
(llvm-lib currently doesn't do this.)
link.exe's /wholearchive seems to only add obj files referenced from the
static library index, but lld-link current really adds all files in the
archive. So if lld-link /wholearchive is used with .lib files produced
by lib.exe and .res files were among the files handed to lib.exe, we
previously silently produced invalid output, but now we error out.

link.exe's /wholearchive semantics on the other hand mean that it
wouldn't load the resource object files from the .lib file at all.
Since this scenario is probably still an unlikely corner case,
the difference in behavior here seems fine -- and lld-link might have to
change to use link.exe's /wholearchive semantics in the future anyways.

Vaguely related to PR42180.

Differential Revision: https://reviews.llvm.org/D63109

llvm-svn: 363078

lld/COFF/Driver.cpp

@@ -971,6 +971,32 @@ static void parsePDBAltPath(StringRef AltPath) {
   Config->PDBAltPath = Buf;
 }
 
+/// Check that at most one resource obj file was used.
+/// Call after ObjFile::Instances is complete.
+static void diagnoseMultipleResourceObjFiles() {
+  // The .rsrc$01 section in a resource obj file contains a tree description
+  // of resources.  Merging multiple resource obj files would require merging
+  // the trees instead of using usual linker section merging semantics.
+  // Since link.exe disallows linking more than one resource obj file with
+  // LNK4078, mirror that.  The normal use of resource files is to give the
+  // linker many .res files, which are then converted to a single resource obj
+  // file internally, so this is not a big restriction in practice.
+  ObjFile *ResourceObjFile = nullptr;
+  for (ObjFile *F : ObjFile::Instances) {
+    if (!F->IsResourceObjFile)
+      continue;
+
+    if (!ResourceObjFile) {
+      ResourceObjFile = F;
+      continue;
+    }
+
+    error(toString(F) +
+          ": more than one resource obj file not allowed, already got " +
+          toString(ResourceObjFile));
+  }
+}
+
 // In MinGW, if no symbols are chosen to be exported, then all symbols are
 // automatically exported by default. This behavior can be forced by the
 // -export-all-symbols option, so that it happens even when exports are
@@ -1812,6 +1838,9 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   if (Config->DoGC)
     markLive(Symtab->getChunks());
 
+  // Needs to happen after the last call to addFile().
+  diagnoseMultipleResourceObjFiles();
+
   // Identify identical COMDAT sections to merge them.
   if (Config->DoICF) {
     findKeepUniqueSections();

lld/COFF/DriverUtils.cpp

@@ -697,6 +697,7 @@ void checkFailIfMismatch(StringRef Arg, InputFile *Source) {
 }
 
 // Convert Windows resource files (.res files) to a .obj file.
+// Does what cvtres.exe does, but in-process and cross-platform.
 MemoryBufferRef convertResToCOFF(ArrayRef<MemoryBufferRef> MBs) {
   object::WindowsResourceParser Parser;
 

lld/COFF/InputFiles.cpp

@@ -206,6 +206,10 @@ SectionChunk *ObjFile::readSection(uint32_t SectionNumber,
   if (Def)
     C->Checksum = Def->CheckSum;
 
+  // link.exe uses the presence of .rsrc$01 for LNK4078, so match that.
+  if (Name == ".rsrc$01")
+    IsResourceObjFile = true;
+
   // CodeView sections are stored to a different vector because they are not
   // linked in the regular manner.
   if (C->isCodeView())
@@ -667,7 +671,8 @@ void ObjFile::initializeFlags() {
 // types of external files: Precomp/PCH OBJs, when compiling with /Yc and /Yu.
 // And PDB type servers, when compiling with /Zi. This function extracts these
 // dependencies and makes them available as a TpiSource interface (see
-// DebugTypes.h).
+// DebugTypes.h). Both cases only happen with cl.exe: clang-cl produces regular
+// output even with /Yc and /Yu and with /Zi.
 void ObjFile::initializeDependencies() {
   if (!Config->Debug)
     return;

lld/COFF/InputFiles.h

@@ -162,10 +162,13 @@ public:
   // precompiled object. Any difference indicates out-of-date objects.
   llvm::Optional<uint32_t> PCHSignature;
 
-  // Tells whether this file was compiled with /hotpatch
+  // Whether this is an object file created from .res files.
+  bool IsResourceObjFile = false;
+
+  // Whether this file was compiled with /hotpatch.
   bool HotPatchable = false;
 
-  // Whether the object was already merged into the final PDB or not
+  // Whether the object was already merged into the final PDB.
   bool MergedIntoPDB = false;
 
   // If the OBJ has a .debug$T stream, this tells how it will be handled.

lld/test/CMakeLists.txt

@@ -34,8 +34,8 @@ configure_lit_site_cfg(
 set(LLD_TEST_DEPS lld)
 if (NOT LLD_BUILT_STANDALONE)
   list(APPEND LLD_TEST_DEPS
-    FileCheck count llc llvm-ar llvm-as llvm-bcanalyzer llvm-config llvm-dis
-    llvm-dwarfdump llvm-lib llvm-mc llvm-nm llvm-objcopy llvm-objdump
+    FileCheck count llc llvm-ar llvm-as llvm-bcanalyzer llvm-config llvm-cvtres
+    llvm-dis llvm-dwarfdump llvm-lib llvm-mc llvm-nm llvm-objcopy llvm-objdump
     llvm-pdbutil llvm-readelf llvm-readobj not obj2yaml opt yaml2obj
     )
 endif()

lld/test/COFF/multiple-resource-objs.test

@@ -0,0 +1,11 @@
+# RUN: llvm-cvtres /out:%t_resource.obj %S/Inputs/resource.res
+# RUN: llvm-cvtres /out:%t_id.obj %S/Inputs/id.res
+# RUN: not lld-link /out:%t.exe /dll /noentry %t_id.obj %t_resource.obj 2>&1 | \
+# RUN:     FileCheck --check-prefix=TWOOBJ %s
+
+TWOOBJ: error: {{.*}}_resource.obj: more than one resource obj file not allowed, already got {{.*}}_id.obj
+
+# RUN: not lld-link /out:%t.exe /dll /noentry %S/Inputs/id.res %t_resource.obj 2>&1 | \
+# RUN:     FileCheck --check-prefix=OBJRES %s
+
+OBJRES: error: internal .obj file created from .res files: more than one resource obj file not allowed, already got {{.*}}_resource.obj

llvm/lib/Object/WindowsResource.cpp

@@ -442,7 +442,8 @@ WindowsResourceCOFFWriter::WindowsResourceCOFFWriter(
       Data(Parser.getData()), StringTable(Parser.getStringTable()) {
   performFileLayout();
 
-  OutputBuffer = WritableMemoryBuffer::getNewMemBuffer(FileSize);
+  OutputBuffer = WritableMemoryBuffer::getNewMemBuffer(
+      FileSize, "internal .obj file created from .res files");
 }
 
 void WindowsResourceCOFFWriter::performFileLayout() {
@@ -521,7 +522,7 @@ void WindowsResourceCOFFWriter::writeCOFFHeader(uint32_t TimeDateStamp) {
   Header->NumberOfSections = 2;
   Header->TimeDateStamp = TimeDateStamp;
   Header->PointerToSymbolTable = SymbolTableOffset;
-  // One symbol for every resource plus 2 for each section and @feat.00
+  // One symbol for every resource plus 2 for each section and 1 for @feat.00
   Header->NumberOfSymbols = Data.size() + 5;
   Header->SizeOfOptionalHeader = 0;
   // cvtres.exe sets 32BIT_MACHINE even for 64-bit machine types. Match it.

llvm/utils/gn/secondary/lld/test/BUILD.gn

@@ -82,6 +82,7 @@ group("test") {
     "//llvm/tools/llvm-ar:symlinks",
     "//llvm/tools/llvm-as",
     "//llvm/tools/llvm-bcanalyzer",
+    "//llvm/tools/llvm-cvtres",
     "//llvm/tools/llvm-dis",
     "//llvm/tools/llvm-dwarfdump",
     "//llvm/tools/llvm-mc",