[lld-macho] Handle multiple LC_LINKER_OPTIONs

[int3]

Summary

We previously only parsed the first one.

[thakis]

lg

Out of interest, how do you end up with an obj file with several of these?

[int3]

lld/test/MachO/lc-linker-option.ll

71

Out of interest, how do you end up with an obj file with several of these?

This line generates multiple LC_LINKER_OPTIONs. So the old test already had multiple, but since they were both -lSystem the issue wasn't noticed

[thakis]

lld/test/MachO/lc-linker-option.ll

71

Well yes, but I mean how do you get clang (or some other compiler) to generate LLVM IR with this? Most people don't write LLVM IR by hand :)

[int3]

lld/test/MachO/lc-linker-option.ll

71

ah gotcha :) The cases I've been seeing are coming from Swift. It seems like Swift generates them even for simple programs:

(base) ~/tmp: cat hello.swift
print("Hello, World!")

(base) ~/tmp: swiftc -c hello.swift
(base) ~/tmp: llvm-objdump --private-headers hello.o | grep LC_LINKER_OPTION
     cmd LC_LINKER_OPTION
     cmd LC_LINKER_OPTION
     cmd LC_LINKER_OPTION

lld/MachO/InputFiles.cpp

error(toString(this) + " has architecture " + getArchitectureName(arch) +
           " which is incompatible with target architecture " +
           getArchitectureName(config->arch()));
     return;
   }
 
   if (!checkCompatibility(this))
     return;
 
-  if (const load_command *cmd = findCommand(hdr, LC_LINKER_OPTION)) {
-    auto *c = reinterpret_cast<const linker_option_command *>(cmd);
-    StringRef data{reinterpret_cast<const char *>(c + 1),
-                   c->cmdsize - sizeof(linker_option_command)};
-    parseLCLinkerOption(this, c->count, data);
+  for (auto *cmd : findCommands<linker_option_command>(hdr, LC_LINKER_OPTION)) {
+    StringRef data{reinterpret_cast<const char *>(cmd + 1),
+                   cmd->cmdsize - sizeof(linker_option_command)};
+    parseLCLinkerOption(this, cmd->count, data);
   }
 
   ArrayRef<Section> sectionHeaders;
   if (const load_command *cmd = findCommand(hdr, LP::segmentLCType)) {
     auto *c = reinterpret_cast<const SegmentCommand *>(cmd);
     sectionHeaders =
         ArrayRef<Section>{reinterpret_cast<const Section *>(c + 1), c->nsects};
     parseSections(sectionHeaders);

lld/test/MachO/lc-linker-option.ll

 ; FRAME-NEXT:    name /usr/lib/libSystem.dylib
 ; FRAME:          cmd LC_LOAD_DYLIB
 ; FRAME-NEXT: cmdsize
 ; FRAME-NEXT:    name /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
 
 ; RUN: llvm-as %t/l.ll -o %t/l.o
 ;; The dynamic call to _CFBigNumGetInt128 uses dyld_stub_binder,
 ;; which needs -lSystem from LC_LINKER_OPTION to get resolved.
+;; The reference to __cxa_allocate_exception will require -lc++ from
+;; LC_LINKER_OPTION to get resolved.
 ; RUN: %lld %t/l.o -o %t/l -framework CoreFoundation
 ; RUN: llvm-otool -l %t/l | FileCheck --check-prefix=LIB %s \
 ; RUN:  --implicit-check-not LC_LOAD_DYLIB
 ; LIB:          cmd LC_LOAD_DYLIB
 ; LIB-NEXT: cmdsize
 ; LIB-NEXT:    name /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
 ; LIB:          cmd LC_LOAD_DYLIB
 ; LIB-NEXT: cmdsize
 ; LIB-NEXT:    name /usr/lib/libSystem.dylib
+; LIB:          cmd LC_LOAD_DYLIB
+; LIB-NEXT: cmdsize
+; LIB-NEXT:    name /usr/lib/libc++abi.dylib
 
 ;; Check that we don't create duplicate LC_LOAD_DYLIBs.
 ; RUN: %lld -lSystem %t/l.o -o %t/l -framework CoreFoundation
-; RUN: llvm-otool -l %t/l | FileCheck --check-prefix=FRAME %s \
+; RUN: llvm-otool -l %t/l | FileCheck --check-prefix=LIB2 %s \
 ; RUN:  --implicit-check-not LC_LOAD_DYLIB
-;
+; LIB2:          cmd LC_LOAD_DYLIB
+; LIB2-NEXT: cmdsize
+; LIB2-NEXT:    name /usr/lib/libSystem.dylib
+; LIB2:          cmd LC_LOAD_DYLIB
+; LIB2-NEXT: cmdsize
+; LIB2-NEXT:    name /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
+; LIB2:          cmd LC_LOAD_DYLIB
+; LIB2-NEXT: cmdsize
+; LIB2-NEXT:    name /usr/lib/libc++abi.dylib
+
 ; RUN: llvm-as %t/invalid.ll -o %t/invalid.o
 ; RUN: not %lld %t/invalid.o -o /dev/null 2>&1 | FileCheck --check-prefix=INVALID %s
 ; INVALID: error: -why_load is not allowed in LC_LINKER_OPTION
 
 ;--- framework.ll
 target triple = "x86_64-apple-macosx10.15.0"
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
 !0 = !{!"-framework", !"CoreFoundation"}
 !llvm.linker.options = !{!0}
 
 declare void @_CFBigNumGetInt128(...)
 
 define void @main() {
   call void bitcast (void (...)* @_CFBigNumGetInt128 to void ()*)()
   ret void
 }
 
 ;--- l.ll
 target triple = "x86_64-apple-macosx10.15.0"
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
 !0 = !{!"-lSystem"}
-!llvm.linker.options = !{!0, !0}
+!1 = !{!"-lc++"}
+!llvm.linker.options = !{!0, !0, !1}
 
 declare void @_CFBigNumGetInt128(...)
+declare i8* @__cxa_allocate_exception(i64)
 
 define void @main() {
   call void bitcast (void (...)* @_CFBigNumGetInt128 to void ()*)()
+  call i8* @__cxa_allocate_exception(i64 4)
   ret void
 }
 
 ;--- invalid.ll
 
 target triple = "x86_64-apple-macosx10.15.0"
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
 !0 = !{!"-why_load"}
 !llvm.linker.options = !{!0}
 
 define void @main() {
   ret void
 }