[lld-macho][wip] Make stabs.s work on Windows

[int3]

Summary

Attempting this after @thakis's comment: https://reviews.llvm.org/D98395#2639561

[int3]

Something weird seems to be happening with the escaping of slashes on the Windows command line... @thakis, any idea why that might happen?

[thakis]

Maybe using %/t (see https://llvm.org/docs/CommandGuide/lit.html#substitutions) in the test could work?

IIRC backslashes doesn't work great with the -D FileCheck due to lit not knowing what the right escape level is. I vaguely remember hitting this somewhere not too long ago. I can't remember what I did about it though :/

lld/MachO/SyntheticSections.cpp

632

Hm, it assumes that the source was compiled with a mach-o triple. Clang hopefully uses slashes when targeting mach-o even on Windows -- if not, that's a bug, right? The host machine shouldn't leak into the target machine. And assuming mach-o slashiness in a mach-o linker seems sensible. So this change here looks good to me, just the FIXME doesn't.

[int3]

Something weird seems to be happening with the escaping of slashes on the Windows command line

I think that's actually a red herring, it's just an artifact of how llvm-lit is printing out stuff. The reason the paths don't match is that lib/Object/Archive.h isn't using the host path separators, so we end up with a mixture of "/" and "\" on Windows. Didn't get around to pinpointing the exact function responsible though.

lld/MachO/SyntheticSections.cpp

632

I guess it depends if we think the main use case after for linking Mach-O on Windows is to do remote debugging or to copy all the files (source and all) to the target machine. I think remote debugging is more likely, in which case the change here is probably wrong...

[int3]

Maybe using %/t (see https://llvm.org/docs/CommandGuide/lit.html#substitutions) in the test could work?

Ah yeah I stumbled across this yesterday... but due to the aforementioned mixed-separator issue it doesn't solve things.

lld/MachO/SyntheticSections.cpp

 
 uint64_t SymtabSection::getRawSize() const {
   return getNumSymbols() * sizeof(structs::nlist_64);
 }
 
 void SymtabSection::emitBeginSourceStab(DWARFUnit *compileUnit) {
   StabsEntry stab(N_SO);
   SmallString<261> dir(compileUnit->getCompilationDir());
-  StringRef sep = sys::path::get_separator();
   // We don't use `path::append` here because we want an empty `dir` to result
   // in an absolute path. `append` would give us a relative path for that case.
-  if (!dir.endswith(sep))
-    dir += sep;
+  // FIXME: This assumes that the source was compiled on a POSIX machine.
+  if (!dir.endswith("/"))
+    dir += "/";
   stab.strx = stringTableSection.addString(
       saver.save(dir + compileUnit->getUnitDIE().getShortName()));
   stabs.emplace_back(std::move(stab));
 }
 
 void SymtabSection::emitEndSourceStab() {
   StabsEntry stab(N_SO);
   stab.sect = 1;

lld/test/MachO/stabs.s

-# REQUIRES: x86, shell
-# UNSUPPORTED: system-windows
+# REQUIRES: x86
 # RUN: rm -rf %t; split-file %s %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/test.s -o %t/test.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/no-debug.s -o %t/no-debug.o
 ## Set modtimes of the files for deterministic test output.
 # RUN: env TZ=UTC touch -t "197001010000.16" %t/test.o
 # RUN: env TZ=UTC touch -t "197001010000.32" %t/foo.o
 # RUN: llvm-ar rcsU %t/foo.a %t/foo.o
 
 # RUN: %lld -lSystem %t/test.o %t/foo.o %t/no-debug.o -o %t/test
-# RUN: (llvm-objdump --section-headers %t/test; llvm-nm -pa %t/test) | \
-# RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o
+# RUN: llvm-objdump --section-headers %t/test > %t/out
+# RUN: llvm-nm -pa %t/test >> %t/out
+# RUN: FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o < %t/out
 
 ## Check that we emit the right modtime even when the object file is in an
 ## archive.
 # RUN: %lld -lSystem %t/test.o %t/foo.a %t/no-debug.o -o %t/test
-# RUN: (llvm-objdump --section-headers %t/test; llvm-nm -pa %t/test) | \
-# RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\)
+# RUN: llvm-objdump --section-headers %t/test > %t/out
+# RUN: llvm-nm -pa %t/test >> %t/out
+# RUN: FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\) < %t/out
 
 ## Check that we emit absolute paths to the object files in our OSO entries
 ## even if our inputs are relative paths.
 # RUN: cd %t && %lld -lSystem test.o foo.o no-debug.o -o test
-# RUN: (llvm-objdump --section-headers %t/test; llvm-nm -pa %t/test) | \
-# RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o
+# RUN: llvm-objdump --section-headers %t/test > %t/out
+# RUN: llvm-nm -pa %t/test >> %t/out
+# RUN: FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o < %t/out
 
 # RUN: cd %t && %lld -lSystem test.o foo.a no-debug.o -o %t/test
-# RUN: (llvm-objdump --section-headers %t/test; llvm-nm -pa %t/test) | \
-# RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\)
+# RUN: llvm-objdump --section-headers %t/test > %t/out
+# RUN: llvm-nm -pa %t/test >> %t/out
+# RUN: FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\) < %t/out
 
 # CHECK:       Sections:
 # CHECK-NEXT:  Idx                Name
 # CHECK-NEXT:  [[#TEXT_ID:]]      __text
 # CHECK-NEXT:  [[#DATA_ID:]]      __data
 # CHECK-NEXT:  [[#MORE_DATA_ID:]] more_data
 # CHECK-NEXT:  [[#COMM_ID:]]      __common
 # CHECK-NEXT:  [[#MORE_TEXT_ID:]] more_text