[ELF] Fix DT_NEEDED value

[davide]

Summary

The absolute path value might not exist at runtime.
To quote Eric Van Gyzen who reported the bug:

18:52 < vangyzen> That path is a build area on the build host.
18:53 < vangyzen> e.g. /build/product/X.Y.Z/lib/libfoo.so
18:54 < vangyzen> On the running product, it's simply /lib.

https://llvm.org/bugs/show_bug.cgi?id=30330

[davide]

Also, the shared.s change is a side effect.
We can't do CHECK-NEXT

[davide]

Also, the shared.s change is a side effect.
We can't do CHECK-NEXT

Section {
  Index: 7
  Name: .dynamic (46)
  Type: SHT_DYNAMIC (0x6)
  Flags [ (0x3)
    SHF_ALLOC (0x2)
    SHF_WRITE (0x1)
  ]
  Address: 0x12000
  Offset: 0x2000
  Size: 96
  Link: 4
  Info: 0
  AddressAlignment: 4
  EntrySize: 8
  SectionData (
    0000: 1D000000 10000000 01000000 18000000  |................|
    0010: 11000000 E4010100 12000000 10000000  |................|
    0020: 13000000 08000000 06000000 50010100  |............P...|
    0030: 0B000000 10000000 05000000 B8010100  |................|
    0040: 0A000000 29000000 04000000 90010100  |....)...........|
    0050: 15000000 00000000 00000000 00000000  |................|
  )
}

because the section data already contains a ).

[ruiu]

Did you check that this behavior matches GNU?

[davide]

In D24363#537577, @ruiu wrote:

Did you check that this behavior matches GNU?

Yes, take a look at the bug report.

[ruiu]

ELF/OutputSections.cpp

689–690 ↗

(On Diff #70745)

Currently, the default soname (used if DT_SONAME is absent) if an absolute path of a library, which I think wrong. Look at SharedFile<ELFT>::parseSoName. You want to fix SoName default value in that function instead of fixing it here.

[ruiu]

ELF/InputFiles.cpp

481

Stripping path parts from the default seems fine, but

494

we should respect DT_SONAME value, no?

[ruiu]

LGTM

test/ELF/shared.s

122

Probably you just want to remove this line.

ELF/InputFiles.cpp

 #include "LinkerScript.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/Analysis.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::sys::fs;
 
 using namespace lld;
case SHT_GNU_versym:
       break;
     case SHT_GNU_verdef:
       this->VerdefSec = &Sec;
       break;
     }
   }
 
   this->initStringTable();
-  SoName = this->getName();
+  SoName = sys::path::filename(this->getName());
 
   if (!DynamicSec)
     return;
   auto *Begin =
       reinterpret_cast<const Elf_Dyn *>(Obj.base() + DynamicSec->sh_offset);
   const Elf_Dyn *End = Begin + DynamicSec->sh_size / sizeof(Elf_Dyn);
 
   for (const Elf_Dyn &Dyn : make_range(Begin, End)) {
     if (Dyn.d_tag == DT_SONAME) {
       uintX_t Val = Dyn.getVal();
       if (Val >= this->StringTable.size())
         fatal(getFilename(this) + ": invalid DT_SONAME entry");
       SoName = StringRef(this->StringTable.data() + Val);
       return;
     }
   }
 }
 
 // Parse the version definitions in the object file if present. Returns a vector
 // whose nth element contains a pointer to the Elf_Verdef for version identifier
 // n. Version identifiers that are not definitions map to nullptr. The array

test/ELF/as-needed-no-reloc.s

 # CHECK:      Name: bar
 # CHECK-NEXT: Value: 0x0
 # CHECK-NEXT: Size: 0
 # CHECK-NEXT: Binding: Global
 # CHECK-NEXT: Type: Function
 # CHECK-NEXT: Other: 0
 # CHECK-NEXT: Section: Undefined
 
-# CHECK: NEEDED SharedLibrary ({{.*}}2.so)
+# CHECK: NEEDED SharedLibrary (as-needed-no-reloc{{.*}}2.so)
 
         .globl _start
 _start:
         .global bar

test/ELF/shared.s

 // CHECK-NEXT:   Offset: [[OFFSET:.*]]
 // CHECK-NEXT:   Size: [[SIZE:.*]]
 // CHECK-NEXT:   Link: [[DYNSTR]]
 // CHECK-NEXT:   Info: 0
 // CHECK-NEXT:   AddressAlignment: [[ALIGN:.*]]
 // CHECK-NEXT:   EntrySize: 8
 // CHECK-NEXT:   SectionData (
 // CHECK:        )
-// CHECK-NEXT: }
+// CHECK: }
 
 // CHECK:      Name: .symtab
 // CHECK-NEXT: Type: SHT_SYMTAB
 // CHECK-NEXT: Flags [
 // CHECK-NEXT: ]
 // CHECK-NEXT: Address:
 // CHECK-NEXT: Offset:
 // CHECK-NEXT: Size: