stdlib: add a missing fixLifetime in withVaList

eeckstein · meg-gupta · commit 20db2a488bab · 2025-01-30T17:30:22.000-08:00
If this function is inlined, the optimizer can shrink the lifetime of the `args` parameter. This would deallocate the passed arguments (e.g. `NSString`s) before the are used in the closure.
diff --git a/stdlib/public/core/VarArgs.swift b/stdlib/public/core/VarArgs.swift
@@ -159,7 +159,9 @@ public func withVaList<R>(_ args: [CVarArg],
   for a in args {
     builder.append(a)
   }
-  return _withVaList(builder, body)
+  let result = _withVaList(builder, body)
+  _fixLifetime(args)
+  return result
 }
 
 /// Invoke `body` with a C `va_list` argument derived from `builder`.

Original file line number	Diff line number	Diff line change
`@@ -159,7 +159,9 @@ public func withVaList<R>(_ args: [CVarArg],`
`159`	`159`	`for a in args {`
`160`	`160`	`builder.append(a)`
`161`	`161`	`}`
`162`		`- return _withVaList(builder, body)`
	`162`	`+ let result = _withVaList(builder, body)`
	`163`	`+ _fixLifetime(args)`
	`164`	`+ return result`
`163`	`165`	`}`
`164`	`166`
`165`	`167`	/// Invoke `body` with a C `va_list` argument derived from `builder`.