[lld][COFF] Add -print-search-paths for debugging.

[thieta]

Summary

While working on adding more implicit search paths to the
lld COFF driver, it was helpful to have a way to print all
the search paths, both for debugging and for testing without
having to create very complicated test cases.

This is a simple arg that just prints the search paths and exits.

[hans]

Seems handy to me. We could also add this kind of info to the /verbose output, but having a separate option is probably more convenient.

lld/COFF/Options.td

301

My ocd noticed that this section of flags seems to be alphabetical.

lld/test/COFF/print-search-paths.s

8

Those backslashes will probably be forward slashes when this test runs on non-Windows.

[thieta]

In D155047#4492920, @hans wrote:

Seems handy to me. We could also add this kind of info to the /verbose output, but having a separate option is probably more convenient.

Yeah, I considered using /verbose first, but it's pretty crowded, and it was harder to see the output when parsing real files. I can add it to verbose *also* if we think that's good?

lld/COFF/Options.td

301

Will fix!

lld/test/COFF/print-search-paths.s

8

Ah good point. Is there a good facility in Filecheck to match the correct slashes?

[mstorsjo]

lld/test/COFF/print-search-paths.s

8

Lots of tests have explicit regexes for it (see e.g. clang/test/Driver), like {{[/\\\\]}}. It's an absolute pain to both write and read though.

[hans]

lld/test/COFF/print-search-paths.s

8

No, I believe the way to do is it with regexes: {{[/\\]}}

[thieta]

lld/test/COFF/print-search-paths.s

8

It's beautiful!

Side-note: maybe we should have a flag to FileCheck or something to allow it to match both or some kind of subst macro.

[hans]

lgtm

[hans]

By the way, do we have a github issue tracking the whole https://discourse.llvm.org/t/improve-autolinking-of-compiler-rt-and-libc-on-windows-with-lld-link/71392/ situation? If so it would be nice to reference it in the commit.

[thieta]

In D155047#4493461, @hans wrote:

By the way, do we have a github issue tracking the whole https://discourse.llvm.org/t/improve-autolinking-of-compiler-rt-and-libc-on-windows-with-lld-link/71392/ situation? If so it would be nice to reference it in the commit.

https://github.com/llvm/llvm-project/issues/63827

Will link all the commits to this.

@mstorsjo are you good with this diff?

[MaskRay]

lld/COFF/Driver.cpp

2065

If we want to behave more like ld.lld, --print-* does not quit early. If we want to behave more like clang driver, options like --print-target-triple quit early. I think the ld.lld style makes more sense.

[thieta]

lld/COFF/Driver.cpp

2065

So print and not exit until the linker normally exits? That seems fine to me, unless anyone objects to that I'll make that change tomorrow.

[mstorsjo]

No objections from me, looks reasonable.

Just make sure the test passes on both unix and Windows - which I believe the premerge CI should cover here. There's always a bit of fiddliness regarding absolute paths and literally checking for matches; e.g. if the tool would happen to renormalize path separator style within that section, that would break. But I believe we use that pattern in a few other places as well so it's most probably fine.

[thieta]

Removed the early exit to behave similar to ld.lld, fixed the tests so they work with this behavior and then I tested all on linux and windows and it seems to work correctly! I think this is good to land.

[phosek]

LGTM

lld/COFF/Config.h

struct Configuration {
   bool debugDwarf = false;
   bool debugGHashes = false;
   bool debugSymtab = false;
   bool driver = false;
   bool driverUponly = false;
   bool driverWdm = false;
   bool showTiming = false;
   bool showSummary = false;
+  bool printSearchPaths = false;
   unsigned debugTypes = static_cast<unsigned>(DebugType::None);
   llvm::SmallVector<llvm::StringRef, 0> mllvmOpts;
   std::vector<std::string> natvisFiles;
   llvm::StringMap<std::string> namedStreams;
   llvm::SmallString<128> pdbAltPath;
   int pdbPageSize = 4096;
   llvm::SmallString<128> pdbPath;
   llvm::SmallString<128> pdbSourcePath;

lld/COFF/Driver.cpp

if (auto *arg = args.getLastArg(OPT_threads)) {
     parallel::strategy = hardware_concurrency(threads);
     config->thinLTOJobs = v.str();
   }
 
   if (args.hasArg(OPT_show_timing))
     config->showTiming = true;
 
   config->showSummary = args.hasArg(OPT_summary);
+  config->printSearchPaths = args.hasArg(OPT_print_search_paths);
 
   // Handle --version, which is an lld extension. This option is a bit odd
   // because it doesn't start with "/", but we deliberately chose "--" to
   // avoid conflict with /version and for compatibility with clang-cl.
   if (args.hasArg(OPT_dash_dash_version)) {
     message(getLLDVersion());
     return;
   }
void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
   // not we assume x64.
   if (config->machine == IMAGE_FILE_MACHINE_UNKNOWN) {
     warn("/machine is not specified. x64 is assumed");
     config->machine = AMD64;
     addWinSysRootLibSearchPaths();
   }
   config->wordsize = config->is64() ? 8 : 4;
 
+  if (config->printSearchPaths) {
+    SmallString<256> buffer;
+    raw_svector_ostream stream(buffer);
+    stream << "Library search paths:\n";
+
+    for (StringRef path : searchPaths)
+      stream << "  " << path << "\n";
+
+    message(buffer);
+  }
+
   // Process files specified as /defaultlib. These must be processed after
   // addWinSysRootLibSearchPaths(), which is why they are in a separate loop.
   for (auto *arg : args.filtered(OPT_defaultlib))
     if (std::optional<StringRef> path = findLibIfNew(arg->getValue()))
       enqueuePath(*path, false, false);
   run();
   if (errorCount())
     return;

lld/COFF/Options.td

 def vfsoverlay : P<"vfsoverlay", "Path to a vfsoverlay yaml file to optionally look for /defaultlib's in">;
 
 // Flags for debugging
 def lldmap : F<"lldmap">;
 def lldmap_file : P_priv<"lldmap">;
 def map : F<"map">;
 def map_file : P_priv<"map">;
 def map_info : P<"mapinfo", "Include the specified information in a map file">;
+def print_search_paths : F<"print-search-paths">;
 def show_timing : F<"time">;
 def summary : F<"summary">;
 
 //==============================================================================
 // The flags below do nothing. They are defined only for link.exe compatibility.
 //==============================================================================
 
 def ignoreidl : F<"ignoreidl">;
 def ltcg : F<"ltcg">;
 def assemblydebug : F<"assemblydebug">;
 def nologo : F<"nologo">;

lld/test/COFF/print-search-paths.s

+# REQUIRES: x86
+# RUN: llvm-mc -triple x86_64-windows-msvc %s -filetype=obj -o %t.obj
+# RUN: lld-link -safeseh:no /dll /noentry /winsysroot:%t.dir/sysroot /vctoolsversion:1.1.1.1 /winsdkversion:10.0.1 %t.obj -print-search-paths | FileCheck -DSYSROOT=%t.dir %s
+# RUN: llvm-mc -triple i686-windows-msvc %s -filetype=obj -o %t_32.obj
+# RUN: lld-link -safeseh:no /dll /noentry /winsysroot:%t.dir/sysroot /vctoolsversion:1.1.1.1 /winsdkversion:10.0.1 %t_32.obj -print-search-paths | FileCheck -DSYSROOT=%t.dir -check-prefix=X86 %s
+# CHECK: Library search paths:
+# CHECK:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}VC{{[/\\]}}Tools{{[/\\]}}MSVC{{[/\\]}}1.1.1.1{{[/\\]}}lib{{[/\\]}}x64
+# CHECK:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}VC{{[/\\]}}Tools{{[/\\]}}MSVC{{[/\\]}}1.1.1.1{{[/\\]}}atlmfc{{[/\\]}}lib{{[/\\]}}x64
+# CHECK:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}Windows Kits{{[/\\]}}10{{[/\\]}}Lib{{[/\\]}}10.0.1{{[/\\]}}ucrt{{[/\\]}}x64
+# CHECK:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}Windows Kits{{[/\\]}}10{{[/\\]}}Lib{{[/\\]}}10.0.1{{[/\\]}}um{{[/\\]}}x64
+# X86: Library search paths:
+# X86:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}VC{{[/\\]}}Tools{{[/\\]}}MSVC{{[/\\]}}1.1.1.1{{[/\\]}}lib{{[/\\]}}x86
+# X86:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}VC{{[/\\]}}Tools{{[/\\]}}MSVC{{[/\\]}}1.1.1.1{{[/\\]}}atlmfc{{[/\\]}}lib{{[/\\]}}x86
+# X86:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}Windows Kits{{[/\\]}}10{{[/\\]}}Lib{{[/\\]}}10.0.1{{[/\\]}}ucrt{{[/\\]}}x86
+# X86:   [[SYSROOT]]{{[/\\]}}sysroot{{[/\\]}}Windows Kits{{[/\\]}}10{{[/\\]}}Lib{{[/\\]}}10.0.1{{[/\\]}}um{{[/\\]}}x86
+
+
+        .text
+        .globl  _main
+_main:
+        ret