[llvm] [SystemZ][z/OS] Add z/OS archive writing support (PR #200087)

[Amy Kwan via llvm-commits]

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@@ -972,6 +1030,15 @@ computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
       if (CurSymFile)
         HasObject = true;
     }
+    // On z/OS, when there are no symbols, add a dummy blank symbol
+    // into the symbol table. This is done since the z/OS binder:
+    //   - emits an error if there is no symbol table in the archive
+    //   - emits an error if the symbol table has 0 symbols
+    //   - should not find any references to a blank symbol
+    if ((LastZosObjIndex == Index) && (SymNames.tell() == 0)) {
+      Symbols.push_back(0);
+      SymNames << ' ' << '\0';
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amy-kwan wrote:

To my understanding, it is necessary as it resolves a binder crash that can possibly happen when we have a 0-length symbol in archive. I believe dding a single character blank suppresses the binder error, not sure if @redstar is able to confirm or shed any insight to this?

https://github.com/llvm/llvm-project/pull/200087