[llvm] [Remarks] Escape control characters in YAML remark arguments and decode them when parsing (PR #227654)

[Florian Hahn via llvm-commits]

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@@ -265,22 +265,21 @@ Expected<StringRef> YAMLRemarkParser::parseKey(yaml::KeyValueNode &Node) {
 }
 
 Expected<StringRef> YAMLRemarkParser::parseStr(yaml::KeyValueNode &Node) {
-  auto *Value = dyn_cast_if_present<yaml::ScalarNode>(Node.getValue());
-  yaml::BlockScalarNode *ValueBlock;
-  StringRef Result;
-  if (!Value) {
-    // Try to parse the value as a block node.
-    ValueBlock = dyn_cast_if_present<yaml::BlockScalarNode>(Node.getValue());
-    if (!ValueBlock)
-      return error("expected a value of scalar type.", Node);
-    Result = ValueBlock->getValue();
-  } else
-    Result = Value->getRawValue();
-
-  Result.consume_front("\'");
-  Result.consume_back("\'");
-
-  return Result;
+  yaml::Node *Value = Node.getValue();
+  // A block value lives in the YAML document, which next() frees before
+  // returning the remark.
+  if (auto *Block = dyn_cast_if_present<yaml::BlockScalarNode>(Value))
+    return Block->getValue().copy(Alloc);
+
+  auto *Scalar = dyn_cast_if_present<yaml::ScalarNode>(Value);
+  if (!Scalar)
+    return error("expected a value of scalar type.", Node);
+  SmallString<32> Storage;
+  StringRef Result = Scalar->getValue(Storage);
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fhahn wrote:

I think this will now write `\0` unescaped if it is contained in the remark string. Could you add a test where we round-trip through bitcode format for a remark string containing `\0`. I think currently it will cut things off.

Perhaps we should just forbid it

https://github.com/llvm/llvm-project/pull/227654