[ELF] Enhance --no-allow-shlib-undefined for non-exported definitions

For a DSO with all DT_NEEDED entries accounted for, if it contains an
undefined non-weak symbol that shares a name with a non-exported
definition (hidden visibility or localized by a version script), and
there is no DSO definition, we should report an error.

#70769 implemented the error when we see `ref.so def-hidden.so`. This patch
implementes the error when we see `def-hidden.so ref.so`, matching GNU
ld.

Close #86777

Author: MaskRay

lld/ELF/InputFiles.cpp

@@ -1557,7 +1557,7 @@ template <class ELFT> void SharedFile::parse() {
       Symbol *s = symtab.addSymbol(
           Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
       s->exportDynamic = true;
-      if (s->isUndefined() && sym.getBinding() != STB_WEAK &&
+      if (sym.getBinding() != STB_WEAK &&
           config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore)
         requiredSymbols.push_back(s);
       continue;

lld/test/ELF/allow-shlib-undefined.s

@@ -31,14 +31,12 @@
 
 ## Test some cases when a relocatable object file provides a non-exported definition.
 # RUN: not ld.lld main.o a.so def-hidden.o -o /dev/null 2>&1 | FileCheck %s --check-prefix=NONEXPORTED
-## TODO
-# RUN: ld.lld main.o def-hidden.o a.so -o /dev/null
+# RUN: not ld.lld main.o def-hidden.o a.so -o /dev/null 2>&1 | FileCheck %s --check-prefix=NONEXPORTED
 # RUN: not ld.lld main.o a.so def-hidden.o -shared --no-allow-shlib-undefined -o /dev/null 2>&1 | FileCheck %s --check-prefix=NONEXPORTED
 # RUN: ld.lld main.o a.so def-hidden.o --allow-shlib-undefined --fatal-warnings -o /dev/null
 ## Test a relocatable object file definition that is converted to STB_LOCAL.
 # RUN: not ld.lld main.o a.so def-hidden.o --version-script=local.ver -o /dev/null 2>&1 | FileCheck %s --check-prefix=NONEXPORTED
-## TODO
-# RUN: ld.lld main.o def-hidden.o a.so --version-script=local.ver -o /dev/null
+# RUN: not ld.lld main.o def-hidden.o a.so --version-script=local.ver -o /dev/null 2>&1 | FileCheck %s --check-prefix=NONEXPORTED
 
 ## The section containing the definition is discarded, and we report an error.
 # RUN: not ld.lld --gc-sections main.o a.so def-hidden.o -o /dev/null 2>&1 | FileCheck %s

lld/test/ELF/shlib-undefined-local.s

@@ -5,10 +5,9 @@
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-linux-gnu -o %t2.o %s
 # RUN: echo "{ local: *; };" > %t.script
-# RUN: ld.lld -version-script %t.script -o %t %t2.o %t.so
-# RUN: llvm-nm -g %t | FileCheck -allow-empty %s
+# RUN: not ld.lld -version-script %t.script %t2.o %t.so -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
 
-# CHECK-NOT: should_not_be_exported
+# ERR: error: non-exported symbol 'should_not_be_exported' in '{{.*}}tmp2.o' is referenced by DSO '{{.*}}tmp.so'
 
 .globl should_not_be_exported
 should_not_be_exported: