[llvm] ee43259 - Initialize output parameters

[Vitaly Buka via llvm-commits]

Author: Vitaly Buka
Date: 2022-01-07T15:21:21-08:00
New Revision: ee43259cbce46a5b979f06710dcfe664473f6a8d

URL: https://github.com/llvm/llvm-project/commit/ee43259cbce46a5b979f06710dcfe664473f6a8d
DIFF: https://github.com/llvm/llvm-project/commit/ee43259cbce46a5b979f06710dcfe664473f6a8d.diff

LOG: Initialize output parameters

If the function returns true, it should
set all output paremeters, similar to Output::preflightElement, or we
have UB on code like:

```
void *SaveInfo;
if (io.preflightFlowElement(i, SaveInfo))
  io.postflightFlowElement(SaveInfo);
```

It's going to be detected by msan with:
-Xclang -enable-noundef-analysis -mllvm -msan-eager-checks=1

Differential Revision: https://reviews.llvm.org/D116826

Added: 
    

Modified: 
    llvm/lib/Support/YAMLTraits.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Support/YAMLTraits.cpp b/llvm/lib/Support/YAMLTraits.cpp
index 10ff020ad972f..416423298bc6d 100644
--- a/llvm/lib/Support/YAMLTraits.cpp
+++ b/llvm/lib/Support/YAMLTraits.cpp
@@ -629,7 +629,7 @@ void Output::endFlowSequence() {
   outputUpToEndOfLine(" ]");
 }
 
-bool Output::preflightFlowElement(unsigned, void *&) {
+bool Output::preflightFlowElement(unsigned, void *&SaveInfo) {
   if (NeedFlowSequenceComma)
     output(", ");
   if (WrapColumn && Column > WrapColumn) {
@@ -639,6 +639,7 @@ bool Output::preflightFlowElement(unsigned, void *&) {
     Column = ColumnAtFlowStart;
     output("  ");
   }
+  SaveInfo = nullptr;
   return true;
 }