[LLD][ELF] - Show symbols visibility in "undefined symbol..." error messages.

[grimar]

Summary

This teaches LLD to report visibility when showing undefined symbol errors
and fixes https://bugs.llvm.org/show_bug.cgi?id=40770.

[grimar]

• Rebased, improved.

Are we going to do this change?

[ruiu]

LGTM

ELF/Relocations.cpp

687

nit: if you make Visibility a std::string, you could remove str(). But perhaps this is slightly more straightforward:

std::string Msg = "undefined ";

if (Sym.Visibility == STV_INTERNAL)
  Msg += "internal ";
else if (Sym.Visibility == STV_HIDDEN)
  Msg += "hidden ";
else if (Sym.Visibility == STV_PROTECTED)
  Msg += "protected ";

Msg += "symbol: " + toString(Sym) + "\n>>> referenced by ";

ELF/Relocations.cpp

static bool maybeReportUndefined(Symbol &Sym, InputSectionBase &Sec,
   if (Sym.isLocal() || !Sym.isUndefined() || Sym.isWeak())
     return false;
 
   bool CanBeExternal =
       Sym.computeBinding() != STB_LOCAL && Sym.Visibility == STV_DEFAULT;
   if (Config->UnresolvedSymbols == UnresolvedPolicy::Ignore && CanBeExternal)
     return false;
 
-  std::string Msg =
-      "undefined symbol: " + toString(Sym) + "\n>>> referenced by ";
+  std::string Visibility = " ";
+  if (Sym.Visibility == STV_INTERNAL)
+    Visibility = " internal ";
+  else if (Sym.Visibility == STV_HIDDEN)
+    Visibility = " hidden ";
+  else if (Sym.Visibility == STV_PROTECTED)
+    Visibility = " protected ";
+
+  std::string Msg = "undefined" + Visibility + "symbol: " + toString(Sym) +
+                    "\n>>> referenced by ";
 
   std::string Src = Sec.getSrcMsg(Sym, Offset);
   if (!Src.empty())
     Msg += Src + "\n>>>               ";
   Msg += Sec.getObjMsg(Offset);
 
   if (Sym.getName().startswith("_ZTV"))
     Msg += "\nthe vtable symbol may be undefined because the class is missing "

test/ELF/executable-undefined-protected-ignoreall.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: not ld.lld %t -o /dev/null --unresolved-symbols=ignore-all -pie 2>&1 | FileCheck %s
-# CHECK: error: undefined symbol: foo
+# CHECK: error: undefined protected symbol: foo
 
 .protected foo
 _start:
 callq foo@PLT

test/ELF/hidden-shared-err.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/hidden-shared-err.s -o %t2.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/hidden-shared-err2.s -o %t3.o
 
 # RUN: ld.lld -shared -o %t2.so %t2.o
 # RUN: not ld.lld %t.o %t2.so -o %t 2>&1 | FileCheck %s
 # RUN: not ld.lld %t2.so %t.o -o %t 2>&1 | FileCheck %s
 
 # RUN: not ld.lld %t.o %t3.o %t2.so -o %t 2>&1 | FileCheck %s
 # RUN: not ld.lld %t3.o %t.o %t2.so -o %t 2>&1 | FileCheck %s
 
-# CHECK: undefined symbol: foo
+# CHECK: undefined hidden symbol: foo
 
 .global _start
 _start:
 .quad foo
 .hidden foo

test/ELF/lto/setting-dso-local.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t1.o
 ; RUN: not ld.lld -o %t %t1.o 2>&1 | FileCheck %s
 
-; CHECK: undefined symbol: foobar
+; CHECK: undefined hidden symbol: foobar
 
 ; We used to crash setting foobar to non-dso_local
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @foobar = external hidden global i32
 define i32* @_start() {
   ret i32* @foobar
 }

test/ELF/undef-shared.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 # RUN: not ld.lld %t.o -o /dev/null -shared 2>&1 | FileCheck %s
 
-# CHECK: error: undefined symbol: hidden
+# CHECK: error: undefined hidden symbol: hidden
 # CHECK: >>> referenced by {{.*}}:(.data+0x0)
 .global hidden
 .hidden hidden
 
-# CHECK: error: undefined symbol: internal
+# CHECK: error: undefined internal symbol: internal
 # CHECK: >>> referenced by {{.*}}:(.data+0x8)
 .global internal
 .internal internal
 
-# CHECK: error: undefined symbol: protected
+# CHECK: error: undefined protected symbol: protected
 # CHECK: >>> referenced by {{.*}}:(.data+0x10)
 .global protected
 .protected protected
 
 .section .data, "a"
  .quad hidden
  .quad internal
  .quad protected

test/ELF/undef-shared2.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/undef-shared2.s -o %t2.o
 # RUN: not ld.lld %t.o %t2.o -o %t.so -shared 2>&1 | FileCheck %s
 # RUN: not ld.lld %t2.o %t.o -o %t.so -shared 2>&1 | FileCheck %s
 
-# CHECK: error: undefined symbol: foo
+# CHECK: error: undefined protected symbol: foo
 
 .data
 .quad foo
 .protected foo

test/ELF/warn-unresolved-symbols-hidden.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: not ld.lld -shared %t.o -o /dev/null -z defs --warn-unresolved-symbols 2>&1| FileCheck %s
 
 # CHECK: warning: undefined symbol: foo
-# CHECK: error: undefined symbol: bar
-# CHECK: error: undefined symbol: zed
+# CHECK: error: undefined hidden symbol: bar
+# CHECK: error: undefined protected symbol: zed
 
 .data
 .quad foo
 .hidden bar
 .quad bar
 .protected zed
 .quad zed