[lld] r239937 - COFF: Create import library files.

Filipe Cabecinhas filcab at gmail.com
Thu Jul 16 14:45:32 PDT 2015


Hi Rui,

On Wed, Jun 17, 2015 at 1:40 PM, Rui Ueyama <ruiu at google.com> wrote:

> Author: ruiu
> Date: Wed Jun 17 15:40:43 2015
> New Revision: 239937
>
> URL: http://llvm.org/viewvc/llvm-project?rev=239937&view=rev
> Log:
> COFF: Create import library files.
>
> On Windows, we have to create a .lib file for each .dll.
> When linking against DLLs, the linker doesn't use the DLL files,
> but instead read a list of dllexported symbols from corresponding
> lib files.
>
> A library file containing descriptors of a DLL is called an
> import library file.
>
> lib.exe has a feature to create an import library file from a
> module-definition file. In this patch, we create a module-definition
> file and pass that to lib.exe.
>
> We eventually want to create an import library file by ourselves
> to eliminate dependency to lib.exe. For now, we just use the MSVC
> tool.
>
> Added:
>     lld/trunk/test/COFF/Inputs/import.yaml
>     lld/trunk/test/COFF/dll.test
> Modified:
>     lld/trunk/COFF/Driver.cpp
>     lld/trunk/COFF/Driver.h
>     lld/trunk/COFF/DriverUtils.cpp
>
> Modified: lld/trunk/COFF/Driver.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.cpp?rev=239937&r1=239936&r2=239937&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Driver.cpp (original)
> +++ lld/trunk/COFF/Driver.cpp Wed Jun 17 15:40:43 2015
> @@ -500,6 +500,11 @@ bool LinkerDriver::link(int Argc, const
>      }
>    }
>
> +  // Windows specific -- when we are creating a .dll file, we also
> +  // need to create a .lib file.
> +  if (!Config->Exports.empty())
> +    writeImportLibrary();
> +
>

^^ Please check the error_code. (Sorry about the delay)

  Filipe


>    // Windows specific -- fix up dllexported symbols.
>    if (!Config->Exports.empty()) {
>      for (Export &E : Config->Exports)
>
> Modified: lld/trunk/COFF/Driver.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.h?rev=239937&r1=239936&r2=239937&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Driver.h (original)
> +++ lld/trunk/COFF/Driver.h Wed Jun 17 15:40:43 2015
> @@ -98,6 +98,7 @@ private:
>  };
>
>  std::error_code parseModuleDefs(MemoryBufferRef MB);
> +std::error_code writeImportLibrary();
>
>  // Functions below this line are defined in DriverUtils.cpp.
>
>
> Modified: lld/trunk/COFF/DriverUtils.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/DriverUtils.cpp?rev=239937&r1=239936&r2=239937&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/DriverUtils.cpp (original)
> +++ lld/trunk/COFF/DriverUtils.cpp Wed Jun 17 15:40:43 2015
> @@ -24,6 +24,8 @@
>  #include "llvm/Option/ArgList.h"
>  #include "llvm/Option/Option.h"
>  #include "llvm/Support/CommandLine.h"
> +#include "llvm/Support/FileUtilities.h"
> +#include "llvm/Support/Path.h"
>  #include "llvm/Support/Process.h"
>  #include "llvm/Support/Program.h"
>  #include "llvm/Support/raw_ostream.h"
> @@ -269,6 +271,75 @@ convertResToCOFF(const std::vector<Memor
>    return MemoryBuffer::getFile(Path);
>  }
>
> +static std::string writeToTempFile(StringRef Contents) {
> +  SmallString<128> Path;
> +  int FD;
> +  if (llvm::sys::fs::createTemporaryFile("tmp", "def", FD, Path)) {
> +    llvm::errs() << "failed to create a temporary file\n";
> +    return "";
> +  }
> +  llvm::raw_fd_ostream OS(FD, /*shouldClose*/ true);
> +  OS << Contents;
> +  return Path.str();
> +}
> +
> +/// Creates a .def file containing the list of exported symbols.
> +static std::string createModuleDefinitionFile() {
> +  std::string S;
> +  llvm::raw_string_ostream OS(S);
> +  OS << "LIBRARY \"" << llvm::sys::path::filename(Config->OutputFile) <<
> "\"\n"
> +     << "EXPORTS\n";
> +  for (Export &E : Config->Exports) {
> +    OS << "  " << E.ExtName;
> +    if (E.Ordinal > 0)
> +      OS << " @" << E.Ordinal;
> +    if (E.Noname)
> +      OS << " NONAME";
> +    if (E.Data)
> +      OS << " DATA";
> +    if (E.Private)
> +      OS << " PRIVATE";
> +    OS << "\n";
> +  }
> +  OS.flush();
> +  return S;
> +}
> +
> +// Creates a .def file and runs lib.exe on it to create an import library.
> +std::error_code writeImportLibrary() {
> +  std::string Prog = "lib.exe";
> +  ErrorOr<std::string> ExeOrErr = llvm::sys::findProgramByName(Prog);
> +  if (auto EC = ExeOrErr.getError()) {
> +    llvm::errs() << "unable to find " << Prog << " in PATH: "
> +                 << EC.message() << "\n";
> +    return make_error_code(LLDError::InvalidOption);
> +  }
> +  llvm::BumpPtrAllocator Alloc;
> +  llvm::BumpPtrStringSaver S(Alloc);
> +  const char *Exe = S.save(ExeOrErr.get());
> +
> +  std::string Contents = createModuleDefinitionFile();
> +  StringRef Def = S.save(StringRef(writeToTempFile(Contents)));
> +  llvm::FileRemover TempFile(Def);
> +
> +  SmallString<128> Out = StringRef(Config->OutputFile);
> +  sys::path::replace_extension(Out, ".lib");
> +
> +  std::vector<const char *> Args;
> +  Args.push_back(Exe);
> +  Args.push_back("/nologo");
> +  Args.push_back("/machine:x64");
> +  Args.push_back(S.save("/def:" + Def));
> +  Args.push_back(S.save("/out:" + Out));
> +  Args.push_back(nullptr);
> +
> +  if (sys::ExecuteAndWait(Exe, Args.data()) != 0) {
> +    llvm::errs() << Exe << " failed\n";
> +    return make_error_code(LLDError::InvalidOption);
> +  }
> +  return std::error_code();
> +}
> +
>  // Create OptTable
>
>  // Create prefix string literals used in Options.td
>
> Added: lld/trunk/test/COFF/Inputs/import.yaml
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/Inputs/import.yaml?rev=239937&view=auto
>
> ==============================================================================
> --- lld/trunk/test/COFF/Inputs/import.yaml (added)
> +++ lld/trunk/test/COFF/Inputs/import.yaml Wed Jun 17 15:40:43 2015
> @@ -0,0 +1,41 @@
> +---
> +header:
> +  Machine:         IMAGE_FILE_MACHINE_AMD64
> +  Characteristics: []
> +sections:
> +  - Name:            .text
> +    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE,
> IMAGE_SCN_MEM_READ ]
> +    Alignment:       4
> +    SectionData:     0000000000000000
> +symbols:
> +  - Name:            .text
> +    Value:           0
> +    SectionNumber:   1
> +    SimpleType:      IMAGE_SYM_TYPE_NULL
> +    ComplexType:     IMAGE_SYM_DTYPE_NULL
> +    StorageClass:    IMAGE_SYM_CLASS_STATIC
> +    SectionDefinition:
> +      Length:          8
> +      NumberOfRelocations: 0
> +      NumberOfLinenumbers: 0
> +      CheckSum:        0
> +      Number:          0
> +  - Name:            mainCRTStartup
> +    Value:           0
> +    SectionNumber:   1
> +    SimpleType:      IMAGE_SYM_TYPE_NULL
> +    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
> +    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
> +  - Name:            exportfn1
> +    Value:           0
> +    SectionNumber:   0
> +    SimpleType:      IMAGE_SYM_TYPE_NULL
> +    ComplexType:     IMAGE_SYM_DTYPE_NULL
> +    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
> +  - Name:            exportfn2
> +    Value:           0
> +    SectionNumber:   0
> +    SimpleType:      IMAGE_SYM_TYPE_NULL
> +    ComplexType:     IMAGE_SYM_DTYPE_NULL
> +    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
> +...
>
> Added: lld/trunk/test/COFF/dll.test
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/dll.test?rev=239937&view=auto
>
> ==============================================================================
> --- lld/trunk/test/COFF/dll.test (added)
> +++ lld/trunk/test/COFF/dll.test Wed Jun 17 15:40:43 2015
> @@ -0,0 +1,19 @@
> +# REQUIRES: winres
> +
> +# RUN: yaml2obj < %p/Inputs/export.yaml > %t.obj
> +# RUN: lld -flavor link2 /out:%t.dll /dll %t.obj /export:exportfn1
> /export:exportfn2
> +# RUN: llvm-objdump -p %t.dll | FileCheck -check-prefix=EXPORT %s
> +
> +EXPORT:      Export Table:
> +EXPORT:      DLL name: dll.test.tmp.dll
> +EXPORT:      Ordinal      RVA  Name
> +EXPORT-NEXT:       0        0
> +EXPORT-NEXT:       1   0x1008  exportfn1
> +EXPORT-NEXT:       2   0x1010  exportfn2
> +
> +# RUN: yaml2obj < %p/Inputs/import.yaml > %t2.obj
> +# RUN: lld -flavor link2 /out:%t2.exe %t2.obj %t.lib
> +# RUN: llvm-readobj -coff-imports %t2.exe | FileCheck
> -check-prefix=IMPORT %s
> +
> +IMPORT: Symbol: exportfn1
> +IMPORT: Symbol: exportfn2
>
>
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