[llvm-readobj] - Always print "Predecessors" for version definition sections.

[grimar]

Summary

This is a follow-up discussed in D70495 thread.

The current logic is unusual for llvm-readobj. It doesn't print predecessors
list when it is empty. This is not good for machine parsers.
D70495 had to add this condition during refactroring to reduce amount of changes,
in tests, because the original code also had a similar logic.

Now seems it is time to get rid of it. This patch does it.

[jhenderson]

LGTM. Might want @MaskRay to confirm.

[MaskRay]

LG. Typo in the description: refactroring -> refactoring.

[ruiu]

LGTM

lld/test/ELF/verdef-defaultver.s

 # DSO-NEXT:    Definition {
 # DSO-NEXT:      Version: 1
 # DSO-NEXT:      Flags [ (0x1)
 # DSO-NEXT:        Base (0x1)
 # DSO-NEXT:      ]
 # DSO-NEXT:      Index: 1
 # DSO-NEXT:      Hash: 127830196
 # DSO-NEXT:      Name: shared
+# DSO-NEXT:      Predecessors: []
 # DSO-NEXT:    }
 # DSO-NEXT:    Definition {
 # DSO-NEXT:      Version: 1
 # DSO-NEXT:      Flags [ (0x0)
 # DSO-NEXT:      ]
 # DSO-NEXT:      Index: 2
 # DSO-NEXT:      Hash: 1425
 # DSO-NEXT:      Name: V1
+# DSO-NEXT:      Predecessors: []
 # DSO-NEXT:    }
 # DSO-NEXT:    Definition {
 # DSO-NEXT:      Version: 1
 # DSO-NEXT:      Flags [ (0x0)
 # DSO-NEXT:      ]
 # DSO-NEXT:      Index: 3
 # DSO-NEXT:      Hash: 1426
 # DSO-NEXT:      Name: V2
+# DSO-NEXT:      Predecessors: []
 # DSO-NEXT:    }
 # DSO-NEXT:  ]
 
 ## Check that we can link against DSO produced.
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t2
 # RUN: ld.lld --hash-style=sysv %t2 %t.so -o %t3
 # RUN: llvm-readobj -V --dyn-syms %t3 | FileCheck --check-prefix=EXE %s
 

lld/test/ELF/verdef-dependency.s

 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x1)
 # DSO-NEXT:       Base (0x1)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 1
 # DSO-NEXT:     Hash: 127830196
 # DSO-NEXT:     Name: shared
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x0)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 2
 # DSO-NEXT:     Hash: 98457184
 # DSO-NEXT:     Name: LIBSAMPLE_1.0
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x0)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 3
 # DSO-NEXT:     Hash: 98456416
 # DSO-NEXT:     Name: LIBSAMPLE_2.0
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x0)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 4
 # DSO-NEXT:     Hash: 98456672
 # DSO-NEXT:     Name: LIBSAMPLE_3.0
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT: ]

lld/test/ELF/verdef.s

 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x1)
 # DSO-NEXT:       Base (0x1)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 1
 # DSO-NEXT:     Hash: 127830196
 # DSO-NEXT:     Name: shared
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x0)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 2
 # DSO-NEXT:     Hash: 98457184
 # DSO-NEXT:     Name: LIBSAMPLE_1.0
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x0)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 3
 # DSO-NEXT:     Hash: 98456416
 # DSO-NEXT:     Name: LIBSAMPLE_2.0
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT:   Definition {
 # DSO-NEXT:     Version: 1
 # DSO-NEXT:     Flags [ (0x0)
 # DSO-NEXT:     ]
 # DSO-NEXT:     Index: 4
 # DSO-NEXT:     Hash: 98456672
 # DSO-NEXT:     Name: LIBSAMPLE_3.0
+# DSO-NEXT:     Predecessors: []
 # DSO-NEXT:   }
 # DSO-NEXT: ]
 # DSO-NEXT: VersionRequirements [
 # DSO-NEXT: ]
 
 ## Check that we can link agains DSO we produced.
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/verdef.s -o %tmain.o
 # RUN: ld.lld --hash-style=sysv %tmain.o %t.so -o %tout

llvm/test/tools/llvm-readobj/elf-versioninfo.test

 # LLVM-NEXT: VersionDefinitions [
 # LLVM-NEXT:   Definition {
 # LLVM-NEXT:     Version: 1
 # LLVM-NEXT:     Flags [ (0x0)
 # LLVM-NEXT:     ]
 # LLVM-NEXT:     Index: 0
 # LLVM-NEXT:     Hash: 0
 # LLVM-NEXT:     Name: VERSION1
+# LLVM-NEXT:     Predecessors: []
 # LLVM-NEXT:   }
 # LLVM-NEXT:   Definition {
 # LLVM-NEXT:     Version: 1
 # LLVM-NEXT:     Flags [ (0x1)
 # LLVM-NEXT:       Base (0x1)
 # LLVM-NEXT:     ]
 # LLVM-NEXT:     Index: 0
 # LLVM-NEXT:     Hash: 0
 # LLVM-NEXT:     Name: VERSION1
+# LLVM-NEXT:     Predecessors: []
 # LLVM-NEXT:   }
 # LLVM-NEXT:   Definition {
 # LLVM-NEXT:     Version: 1
 # LLVM-NEXT:     Flags [ (0x2)
 # LLVM-NEXT:       Weak (0x2)
 # LLVM-NEXT:     ]
 # LLVM-NEXT:     Index: 0
 # LLVM-NEXT:     Hash: 0
 # LLVM-NEXT:     Name: VERSION1
+# LLVM-NEXT:     Predecessors: []
 # LLVM-NEXT:   }
 # LLVM-NEXT:   Definition {
 # LLVM-NEXT:     Version: 1
 # LLVM-NEXT:     Flags [ (0x4)
 # LLVM-NEXT:       Info (0x4)
 # LLVM-NEXT:     ]
 # LLVM-NEXT:     Index: 0
 # LLVM-NEXT:     Hash: 0
 # LLVM-NEXT:     Name: VERSION1
+# LLVM-NEXT:     Predecessors: []
 # LLVM-NEXT:   }
 # LLVM-NEXT:   Definition {
 # LLVM-NEXT:     Version: 1
 # LLVM-NEXT:     Flags [ (0x7)
 # LLVM-NEXT:       Base (0x1)
 # LLVM-NEXT:       Info (0x4)
 # LLVM-NEXT:       Weak (0x2)
 # LLVM-NEXT:     ]
 # LLVM-NEXT:     Index: 2
 # LLVM-NEXT:     Hash: 175630257
 # LLVM-NEXT:     Name: VERSION1
+# LLVM-NEXT:     Predecessors: []
 # LLVM-NEXT:   }
 # LLVM-NEXT:   Definition {
 # LLVM-NEXT:     Version: 1
 # LLVM-NEXT:     Flags [ (0x8)
 # LLVM-NEXT:     ]
 # LLVM-NEXT:     Index: 3
 # LLVM-NEXT:     Hash: 175630258
 # LLVM-NEXT:     Name: VERSION2

 # PAST-STRTAB-END-LLVM:      VersionDefinitions [
 # PAST-STRTAB-END-LLVM-NEXT:   Definition {
 # PAST-STRTAB-END-LLVM-NEXT:     Version: 0
 # PAST-STRTAB-END-LLVM-NEXT:     Flags [ (0x0)
 # PAST-STRTAB-END-LLVM-NEXT:     ]
 # PAST-STRTAB-END-LLVM-NEXT:     Index: 0
 # PAST-STRTAB-END-LLVM-NEXT:     Hash: 0
 # PAST-STRTAB-END-LLVM-NEXT:     Name: <invalid vda_name: 5>
+# PAST-STRTAB-END-LLVM-NEXT:     Predecessors: []
 # PAST-STRTAB-END-LLVM-NEXT:   }
 # PAST-STRTAB-END-LLVM-NEXT: ]
 
 # PAST-STRTAB-END-GNU:      Version definition section '.gnu.version_d' contains 1 entries:
 # PAST-STRTAB-END-GNU-NEXT:  Addr: 0000000000000000  Offset: 0x000040  Link: 2 (.strtab)
 # PAST-STRTAB-END-GNU-NEXT:   0x0000: Rev: 0  Flags: none  Index: 0  Cnt: 1  Name: <invalid vda_name: 5>
 
 --- !ELF

llvm/test/tools/yaml2obj/ELF/verdef-section.yaml

 ## Check we are able to handle SHT_GNU_verdef sections.
 
 # RUN: yaml2obj --docnum=1 %s -o %t1
 # RUN: llvm-readobj -V %t1 | FileCheck %s
 
 # CHECK:      VersionDefinitions [
 # CHECK-NEXT:   Definition {
 # CHECK-NEXT:     Version: 1
 # CHECK-NEXT:     Flags [ (0x1)
 # CHECK-NEXT:       Base (0x1)
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Index: 1
 # CHECK-NEXT:     Hash: 170240160
 # CHECK-NEXT:     Name: dso.so.0
+# CHECK-NEXT:     Predecessors: []
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Definition {
 # CHECK-NEXT:     Version: 1
 # CHECK-NEXT:     Flags [ (0x2)
 # CHECK-NEXT:       Weak (0x2)
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Index: 2
 # CHECK-NEXT:     Hash: 108387921
 # CHECK-NEXT:     Name: VERSION_1
+# CHECK-NEXT:     Predecessors: []
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Definition {
 # CHECK-NEXT:     Version: 1
 # CHECK-NEXT:     Flags [ (0x3)
 # CHECK-NEXT:       Base (0x1)
 # CHECK-NEXT:       Weak (0x2)
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Index: 3

llvm/tools/llvm-readobj/ELFDumper.cpp

void LLVMStyle<ELFT>::printVersionDefinitionSection(const ELFFile<ELFT> *Obj,
 
   for (const VerDef &D : *V) {
     DictScope Def(W, "Definition");
     W.printNumber("Version", D.Version);
     W.printFlags("Flags", D.Flags, makeArrayRef(SymVersionFlags));
     W.printNumber("Index", D.Ndx);
     W.printNumber("Hash", D.Hash);
     W.printString("Name", D.Name.c_str());
-
-    if (D.AuxV.empty())
-      continue;
     W.printList(
         "Predecessors", D.AuxV,
         [](raw_ostream &OS, const VerdAux &Aux) { OS << Aux.Name.c_str(); });
   }
 }
 
 template <class ELFT>
 void LLVMStyle<ELFT>::printVersionDependencySection(const ELFFile<ELFT> *Obj,