[COFF] Don't error if the only inputs are from /wholearchive:

[rnk]

Summary

Fixes PR43744

[boris]

LGTM

[amccarth]

This looks like the right approach, but I have a concern or two about the ramifications as noted inline. Let me know if my concerns are unwarranted.

lld/COFF/Driver.cpp

1168

I don't entirely understand the meaning of noEntry here, but your change affects whether this happens or not. Is that important? I don't know. See my comment on your new test.

1730

This seems like a possible problem. Before, you couldn't get here without OPT_INPUTs--you either had some, or you had a DEF file which would provide the output file name. Now we can get here with just an archive, so we might be dereferencing an iterator at the beginning of an empty list.

lld/test/COFF/wholearchive.s

18

I think the -out flag is preventing the potential crasher I mentioned above. Can you try it without the -out?

Maybe we need one with a DEF file as well.

[smeenai]

Somewhat related to the comments, I believe lld-link's ability to generate an import library from a def file directly is non-standard. MSVC's toolchain requires you to go through lib for that.

[rnk]

lld/COFF/Driver.cpp

1683

This also ended up being a bug caught by the entry inference test.

1730

Thanks, that's a real bug. I checked the Visual C++ linker's behavior, and they name the output after the first wholearchive argument. I did this: link -wholearchive:foo.lib and it produced foo.exe.

lld/test/COFF/wholearchive.s

18

I updated two existing tests that deal with infering things from inputs:

1. out.test, this infers the .exe name from the wholearchive name
2. entry-inference.test, this deals with inferring the entry point, which interacts with deffile and noentry.

I don't think the case of -def: -wholearchive: is interesting, the def file is going to control the name of the DLL in that case.

[rnk]

• fix bugs

lld/COFF/Driver.cpp

if (Optional<std::string> path = getReproduceFile(args)) {
     if (errOrWriter) {
       tar = std::move(*errOrWriter);
     } else {
       error("/linkrepro: failed to open " + *path + ": " +
             toString(errOrWriter.takeError()));
     }
   }
 
-  if (!args.hasArg(OPT_INPUT)) {
+  if (!args.hasArg(OPT_INPUT, OPT_wholearchive_file)) {
     if (args.hasArg(OPT_deffile))
       config->noEntry = true;
     else
       fatal("no input files");
   }
 
   // Construct search path list.
   searchPaths.push_back("");
   for (auto *arg : args.filtered(OPT_libpath))
     searchPaths.push_back(arg->getValue());
void LinkerDriver::link(ArrayRef<const char *> argsArr) {
 
   // Handle /def
   if (auto *arg = args.getLastArg(OPT_deffile)) {
     // parseModuleDefs mutates Config object.
     parseModuleDefs(arg->getValue());
   }
 
   // Handle generation of import library from a def file.
   if (!args.hasArg(OPT_INPUT)) {
     fixupExports();
     createImportLibrary(/*asLib=*/true);
     return;
   }
 
   // Windows specific -- if no /subsystem is given, we need to infer
   // that from entry point name.  Must happen before /entry handling,
   // and after the early return when just writing an import library.
for (auto *arg : args.filtered(OPT_delayload)) {
     } else {
       config->delayLoadHelper = addUndefined("__delayLoadHelper2");
     }
   }
 
   // Set default image name if neither /out or /def set it.
   if (config->outputFile.empty()) {
     config->outputFile =
         getOutputPath((*args.filtered(OPT_INPUT).begin())->getValue());
   }
 
   // Fail early if an output file is not writable.
   if (auto e = tryCreateFile(config->outputFile)) {
     error("cannot open output file " + config->outputFile + ": " + e.message());
     return;
   }
 

lld/test/COFF/wholearchive.s

 # REQUIRES: x86
 
 # RUN: yaml2obj < %p/Inputs/export.yaml > %t.archive.obj
 # RUN: rm -f %t.archive.lib
 # RUN: llvm-ar rcs %t.archive.lib %t.archive.obj
 # RUN: llvm-mc -triple=x86_64-windows-msvc %s -filetype=obj -o %t.main.obj
 
 # RUN: lld-link -dll -out:%t.dll -entry:main %t.main.obj -wholearchive:%t.archive.lib -implib:%t.lib
 # RUN: llvm-readobj %t.lib | FileCheck %s -check-prefix CHECK-IMPLIB
 
 # RUN: lld-link -dll -out:%t.dll -entry:main %t.main.obj -wholearchive %t.archive.lib -implib:%t.lib
 # RUN: llvm-readobj %t.lib | FileCheck %s -check-prefix CHECK-IMPLIB
 
 # RUN: lld-link -dll -out:%t.dll -entry:main %t.main.obj %t.archive.lib -wholearchive:%t.archive.lib -implib:%t.lib
 # RUN: llvm-readobj %t.lib | FileCheck %s -check-prefix CHECK-IMPLIB
 
+# PR43744: Test no inputs except a whole archive.
+# RUN: lld-link -dll -out:%t.dll -noentry -wholearchive:%t.archive.lib -implib:%t.lib
+# RUN: llvm-readobj %t.lib | FileCheck %s -check-prefix CHECK-IMPLIB
+
 # RUN: mkdir -p %t.dir
 # RUN: cp %t.archive.lib %t.dir/foo.lib
 # RUN: lld-link -dll -out:%t.dll -entry:main -libpath:%t.dir %t.main.obj %t.dir/./foo.lib -wholearchive:foo.lib -implib:%t.lib
 # RUN: llvm-readobj %t.lib | FileCheck %s -check-prefix CHECK-IMPLIB
 
 # CHECK-IMPLIB: Symbol: __imp_exportfn3
 # CHECK-IMPLIB: Symbol: exportfn3
 
 .global main
 .text
 main:
   ret