[ELF] Don't set versionId on undefined weak lazy symbols

[MaskRay]

Summary

An unfetched lazy symbol (undefined weak) should be considered to have its
original versionId which is VER_NDX_GLOBAL, instead of the lazy symbol's
versionId. (The original versionId cannot be non-VER_NDX_GLOBAL because a
undefined versioned symbol is an error.)

The regression was introduced in D77280 when making version scripts work
with lazy symbols fetched by LTO calls.

Fix PR49915

lld/ELF/SyntheticSections.cpp

 
 size_t VersionTableSection::getSize() const {
   return (getPartition().dynSymTab->getSymbols().size() + 1) * 2;
 }
 
 void VersionTableSection::writeTo(uint8_t *buf) {
   buf += 2;
   for (const SymbolTableEntry &s : getPartition().dynSymTab->getSymbols()) {
-    write16(buf, s.sym->versionId);
+    write16(buf, s.sym->isLazy() ? VER_NDX_GLOBAL : s.sym->versionId);
     buf += 2;
   }
 }
 
 bool VersionTableSection::isNeeded() const {
   return isLive() &&
          (getPartition().verDef || getPartition().verNeed->isNeeded());
 }

lld/test/ELF/version-script-weak.s

 # CHECK-NEXT:   Value: 0x0
 # CHECK-NEXT:   Size: 0
 # CHECK-NEXT:   Binding: Weak
 # CHECK-NEXT:   Type: None
 # CHECK-NEXT:   Other: 0
 # CHECK-NEXT:   Section: Undefined
 # CHECK-NEXT: }
 
+## The version of an unfetched lazy symbol is VER_NDX_GLOBAL. It is not affected by version scripts.
+# RUN: echo "v1 { *; };" > %t2.script
+# RUN: ld.lld -shared --version-script %t2.script %t.o --start-lib %t1.o --end-lib -o %t2.so
+# RUN: llvm-readelf -V %t2.so | FileCheck %s --check-prefix=CHECK2
+
+# CHECK2: 000: 0 (*local*) 1 (*global*)
+
+# RUN: ld.lld -shared --soname=tshared --version-script %t2.script %t1.o -o %tshared.so
+# RUN: ld.lld -shared --version-script %t2.script %t.o --start-lib %t1.o --end-lib %tshared.so -o %t3.so
+# RUN: llvm-readelf -V %t3.so | FileCheck %s --check-prefix=CHECK3
+
+# CHECK3: 000: 0 (*local*) 3 (v1)
+
 .text
  callq foo@PLT
 .weak foo