[LinkerWrapper] report on missing libraries

[jhuber6]

Summary

The linker wrapper does its own library searching for static archives
that can contain device code. The device linking phases happen before
the host linking phases so that we can generate the necessary
registration code and link it in with the rest of the code. Previously,
If a library containing needed device code was not found the execution
would continue silently until it failed with undefined symbols. This
patch allows the linker wrapper to perform its own check beforehand to
catch these errors.

[jdoerfert]

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

1278

So if the library is found but not an archive we silently continue still?

[jhuber6]

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

1278

In that case it won't be used for device linking so the host linker will handle that.

[jdoerfert]

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

1278

Can you add a comment, I still don't understand when/how this happens but a comment might do.

[jhuber6]

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

1278

Sorry I didn't explain the logic correctly. The else means that we will error on any library that's found but not present in the linker wrapper. This conditional simply ensures that we only attempt to extract offloading files if it's in a static library.

[jdoerfert]

LG

clang/test/Driver/linker-wrapper.c

 // CUDA: fatbinary{{.*}}-64 --create {{.*}}.fatbin --image=profile=sm_52,file={{.*}}.out --image=profile=sm_70,file={{.*}}.out
 
 // RUN: clang-offload-packager -o %t.out \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=hip,triple=amdgcn-amd-amdhsa,arch=gfx90a \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=openmp,triple=amdgcn-amd-amdhsa,arch=gfx90a \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=hip,triple=amdgcn-amd-amdhsa,arch=gfx908
 // RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o \
 // RUN:   -fembed-offload-object=%t.out
-// RUN: clang-linker-wrapper --dry-run --host-triple=x86_64-unknown-linux-gnu -linker-path \
-// RUN:   /usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=HIP
+// RUN: clang-linker-wrapper --dry-run --host-triple=x86_64-unknown-linux-gnu \
+// RUN:   --linker-path=/usr/bin/ld -- %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=HIP
 
 // HIP: lld{{.*}}-flavor gnu --no-undefined -shared -plugin-opt=-amdgpu-internalize-symbols -plugin-opt=mcpu=gfx908 -o {{.*}}.out {{.*}}.o
 // HIP: lld{{.*}}-flavor gnu --no-undefined -shared -plugin-opt=-amdgpu-internalize-symbols -plugin-opt=mcpu=gfx90a -o {{.*}}.out {{.*}}.o
 // HIP: clang-offload-bundler{{.*}}-type=o -bundle-align=4096 -targets=host-x86_64-unknown-linux,hipv4-amdgcn-amd-amdhsa--gfx908,hipv4-amdgcn-amd-amdhsa--gfx90a -input=/dev/null -input={{.*}}.out -input={{.*}}out -output={{.*}}.hipfb
 
 // RUN: clang-offload-packager -o %t.out \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=openmp,triple=amdgcn-amd-amdhsa,arch=gfx908 \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=openmp,triple=nvptx64-nvidia-cuda,arch=sm_70
 // RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o \
 // RUN:   -fembed-offload-object=%t.out
 // RUN: clang-linker-wrapper --dry-run --host-triple=x86_64-unknown-linux-gnu \
 // RUN:   --linker-path=/usr/bin/ld --device-linker=a --device-linker=nvptx64-nvidia-cuda=b -- \
 // RUN:   %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=LINKER_ARGS
 
 // LINKER_ARGS: lld{{.*}}-flavor gnu --no-undefined -shared -plugin-opt=-amdgpu-internalize-symbols -plugin-opt=mcpu=gfx908 -o {{.*}}.out {{.*}}.o a
 // LINKER_ARGS: nvlink{{.*}}-m64 -o {{.*}}.out -arch sm_70 {{.*}}.o a b
 
+// RUN: not clang-linker-wrapper --dry-run --host-triple=x86_64-unknown-linux-gnu -ldummy \
+// RUN:   --linker-path=/usr/bin/ld --device-linker=a --device-linker=nvptx64-nvidia-cuda=b -- \
+// RUN:   -o a.out 2>&1 | FileCheck %s --check-prefix=MISSING-LIBRARY
+
+// MISSING-LIBRARY: error: unable to find library -ldummy
+
 /// Ensure that temp files aren't leftoever from static libraries.
 // RUN: clang-offload-packager -o %t-lib.out \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=openmp,triple=nvptx64-nvidia-cuda,arch=sm_70 \
 // RUN:   --image=file=%S/Inputs/dummy-elf.o,kind=cuda,triple=nvptx64-nvidia-cuda,arch=sm_52
 // RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o -fembed-offload-object=%t-lib.out
 // RUN: llvm-ar rcs %t.a %t.o
 // RUN: rm -f %t.o
 // RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t-obj.o
 // RUN: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --dry-run --save-temps \
 // RUN:   --linker-path=/usr/bin/ld -- %t.a %t-obj.o -o a.out
 // RUN: not ls "*-device-*"

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

if (Optional<std::string> File = findFile(Dir, Root, Name))
       return File;
   return None;
 }
 
 Optional<std::string> searchLibraryBaseName(StringRef Name, StringRef Root,
                                             ArrayRef<StringRef> SearchPaths) {
   for (StringRef Dir : SearchPaths) {
     if (Optional<std::string> File = findFile(Dir, Root, "lib" + Name + ".so"))
-      return None;
+      return File;
     if (Optional<std::string> File = findFile(Dir, Root, "lib" + Name + ".a"))
       return File;
   }
   return None;
 }
 
 /// Search for static libraries in the linker's library path given input like
 /// `-lfoo` or `-l:libfoo.a`.
for (const opt::Arg *Arg : Args.filtered(OPT_INPUT)) {
 
     bool IsLazy =
         identify_magic((*BufferOrErr)->getBuffer()) == file_magic::archive;
     if (Error Err = extractOffloadBinaries(
             **BufferOrErr, IsLazy ? LazyInputFiles : InputFiles))
       return std::move(Err);
   }
 
-  // Try to extract input from input libraries.
+  // Try to extract input from input archive libraries.
   for (const opt::Arg *Arg : Args.filtered(OPT_library)) {
     if (auto Library = searchLibrary(Arg->getValue(), Root, LibraryPaths)) {
       ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
           MemoryBuffer::getFileOrSTDIN(*Library);
       if (std::error_code EC = BufferOrErr.getError())
         reportError(createFileError(*Library, EC));
 
+      if (identify_magic((*BufferOrErr)->getBuffer()) != file_magic::archive)
+        continue;
+
       if (Error Err = extractOffloadBinaries(**BufferOrErr, LazyInputFiles))
         return std::move(Err);
+    } else {
+      reportError(createStringError(inconvertibleErrorCode(),
+                                    "unable to find library -l%s",
+                                    Arg->getValue()));
     }
   }
 
   for (StringRef Library : Args.getAllArgValues(OPT_bitcode_library_EQ)) {
     auto FileOrErr = getInputBitcodeLibrary(Library);
     if (!FileOrErr)
       return FileOrErr.takeError();
     InputFiles.push_back(std::move(*FileOrErr));