[flang-commits] [flang] [flang][debug] Handle allocatable strings. (PR #95906)

[via flang-commits]

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@@ -205,16 +205,38 @@ mlir::LLVM::DITypeAttr DebugTypeGenerator::convertCharacterType(
   if (charTy.getFKind() != 1)
     encoding = llvm::dwarf::DW_ATE_UCS;
 
+  uint64_t sizeInBits = 0;
+  mlir::LLVM::DIExpressionAttr lenExpr = nullptr;
+  mlir::LLVM::DIExpressionAttr locExpr = nullptr;
+
+  if (allocatable) {
+    llvm::SmallVector<mlir::LLVM::DIExpressionElemAttr> ops;
+    auto addOp = [&](unsigned opc, llvm::ArrayRef<uint64_t> vals) {
+      ops.push_back(mlir::LLVM::DIExpressionElemAttr::get(context, opc, vals));
+    };
+    addOp(llvm::dwarf::DW_OP_push_object_address, {});
+    addOp(llvm::dwarf::DW_OP_plus_uconst, {lenOffset});
+    lenExpr = mlir::LLVM::DIExpressionAttr::get(context, ops);
+    ops.clear();
+
+    addOp(llvm::dwarf::DW_OP_push_object_address, {});
+    addOp(llvm::dwarf::DW_OP_deref, {});
+    locExpr = mlir::LLVM::DIExpressionAttr::get(context, ops);
+  } else if (charTy.hasConstantLen()) {
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jeanPerier wrote:

Technically, I think it would be valid to fall here first. Allocatable may have non deferred length parameter. 
For instance:

```
module m
character(len=16), allocatable :: str2
end module

 use m
 str2 = "hello" ! still length 16, padding is added.
end
```

It is still valid to read the descriptor that should also contain 16, but maybe it makes more sense to give the simpler description without a DIExpressionAttr. Do you know which DWARF must be generated here?

https://github.com/llvm/llvm-project/pull/95906