[AVR][clang] Fix a bug in AVR toolchain search paths

[benshi001]

Summary

Current AVR clang driver assumes sysroot to be fixed "/" and omits
user specified "--sysroot" option. And this patch fixes that.

[MaskRay]

clang/lib/Driver/ToolChains/AVR.cpp

367

This should call ToolChain::GetProgramPath instead

[benshi001]

There is a use of GetProgramPath at above line.

std::string Linker = getToolChain().GetProgramPath(getShortName());

I use a better solution that add user specified sysroot to ProgramPath via GetProgramPaths.push_back().

[benshi001]

The test "make check-clang-driver -j8" passes both with and without avr-ld/avr-libc installed.

[MaskRay]

clang/lib/Driver/ToolChains/AVR.cpp

426

My feeling is that empty --sysroot should mean /, instead of /usr. You probably need to read other ToolChains/*.cpp files first

[benshi001]

I also think that sysroot means /, but the basic_riscv32_tree seems to assume sysroot to be /usr. However I change my patch to / as you suggested.

[MaskRay]

clang/lib/Driver/ToolChains/AVR.cpp

339

Would be nice not needing to hard code /usr/bin. How do other toolchains do?

341

Mixed tab and space?

424

= getDriver().SysRoot

[benshi001]

clang/lib/Driver/ToolChains/AVR.cpp

339

Would be nice not needing to hard code /usr/bin. How do other toolchains do?

Many toolchains just use GCC's program paths, which auto include user specified sysroot. So I simplify it use AVR-GCCInstallation as first choice, then class ToolChain's default behavior.

clang/lib/Driver/ToolChains/AVR.cpp

if (CPU.empty()) {
         // No avr-gcc found and so no runtime linked.
         D.Diag(diag::warn_drv_avr_gcc_not_found);
       } else if (!AVRLibcRoot.hasValue()) {
         // No avr-libc found and so no runtime linked.
         D.Diag(diag::warn_drv_avr_libc_not_found);
       } else { // We have enough information to link stdlibs
         std::string GCCRoot = std::string(GCCInstallation.getInstallPath());
         std::string LibcRoot = AVRLibcRoot.getValue();
         std::string SubPath = GetMCUSubPath(CPU);
 
         getFilePaths().push_back(LibcRoot + std::string("/lib/") + SubPath);
         getFilePaths().push_back(GCCRoot + std::string("/") + SubPath);
 
         LinkStdlib = true;
       }
     }
 
     if (!LinkStdlib)
       D.Diag(diag::warn_drv_avr_stdlib_not_linked);
void AVR::Linker::ConstructJob(Compilation &C, const JobAction &JA,
                                const InputInfoList &Inputs, const ArgList &Args,
                                const char *LinkingOutput) const {
   // Compute information about the target AVR.
   std::string CPU = getCPUName(Args, getToolChain().getTriple());
   llvm::Optional<StringRef> FamilyName = GetMCUFamilyName(CPU);
   llvm::Optional<unsigned> SectionAddressData = GetMCUSectionAddressData(CPU);
 
   std::string Linker = getToolChain().GetProgramPath(getShortName());
+  if (!getToolChain().getDriver().SysRoot.empty())
+    Linker = getToolChain().getDriver().SysRoot + Linker;
   ArgStringList CmdArgs;
   AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs, JA);
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   // Enable garbage collection of unused sections.
   CmdArgs.push_back("--gc-sections");
void AVR::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
   C.addCommand(std::make_unique<Command>(
       JA, *this, ResponseFileSupport::AtFileCurCP(), Args.MakeArgString(Linker),
       CmdArgs, Inputs, Output));
 }
 
 llvm::Optional<std::string> AVRToolChain::findAVRLibcInstallation() const {
   for (StringRef PossiblePath : PossibleAVRLibcLocations) {
+    std::string Path(getDriver().SysRoot.empty() ? "" : getDriver().SysRoot);
+    Path += PossiblePath.str();
     // Return the first avr-libc installation that exists.
-    if (llvm::sys::fs::is_directory(PossiblePath))
-      return Optional<std::string>(std::string(PossiblePath));
+    if (llvm::sys::fs::is_directory(Path))
+      return Optional<std::string>(Path);
   }
 
   return llvm::None;
 }

clang/test/Driver/avr-ld.c

+// RUN: %clang -### --target=avr -mmcu=atmega328 --sysroot %S/Inputs/basic_avr_tree %s 2>&1 | FileCheck -check-prefix LINK %s
+// LINK: {{".*ld.*"}} {{.*}} {{"-L.*avr5"}} {{.*}} "-Tdata=0x800100" {{.*}} "-latmega328" "-mavr5"