[Backtracing][Linux] Remove status argument.

The `status` argument to the `_swift_backtrace_demangle()` function
isn't especially useful, won't match behaviour on Windows, and we
actually don't use it in the Swift code that calls this SPI.

Remove it.

rdar://110261712

Author: al45tair

include/swift/Runtime/Backtrace.h

@@ -146,7 +146,6 @@ bool _swift_backtrace_isThunkFunction(const char *mangledName);
 /// @param outputBuffer is a pointer to a buffer in which to place the result.
 /// @param outputBufferSize points to a variable that contains the size of the
 /// output buffer.
-/// @param status returns the status codes defined in the C++ ABI.
 ///
 /// If outputBuffer is nullptr, the function will allocate memory for the
 /// result using malloc().  In this case, outputBufferSize may be nullptr;
@@ -168,8 +167,7 @@ SWIFT_RUNTIME_STDLIB_SPI
 char *_swift_backtrace_demangle(const char *mangledName,
                                 size_t mangledNameLength,
                                 char *outputBuffer,
-                                size_t *outputBufferSize,
-                                int *status);
+                                size_t *outputBufferSize);
 #ifdef __cplusplus
 } // namespace backtrace
 } // namespace runtime

stdlib/public/Backtracing/SymbolicatedBacktrace.swift

@@ -200,9 +200,8 @@ public struct SymbolicatedBacktrace: CustomStringConvertible {
     /// Demangle the raw name, if possible.
     private func demangleRawName() -> String {
       var length: size_t = 0
-      var status: CInt = 0
       if let demangled = _swift_backtrace_demangle(rawName, rawName.utf8.count,
-                                                   nil, &length, &status) {
+                                                   nil, &length) {
         defer { free(demangled) }
 
         // length is the size of the buffer that was allocated, *not* the

stdlib/public/runtime/Backtrace.cpp

@@ -855,8 +855,7 @@ SWIFT_RUNTIME_STDLIB_SPI char *
 _swift_backtrace_demangle(const char *mangledName,
                           size_t mangledNameLength,
                           char *outputBuffer,
-                          size_t *outputBufferSize,
-                          int *status) {
+                          size_t *outputBufferSize) {
   llvm::StringRef name = llvm::StringRef(mangledName, mangledNameLength);
 
   // You must provide buffer size if you're providing your own output buffer
@@ -884,13 +883,13 @@ _swift_backtrace_demangle(const char *mangledName,
     ::memcpy(outputBuffer, result.data(), toCopy);
     outputBuffer[toCopy] = '\0';
 
-    *status = 0;
     return outputBuffer;
 #ifndef _WIN32
   } else if (name.startswith("_Z")) {
     // Try C++
     size_t resultLen;
-    char *result = abi::__cxa_demangle(mangledName, nullptr, &resultLen, status);
+    int status = 0;
+    char *result = abi::__cxa_demangle(mangledName, nullptr, &resultLen, &status);
 
     if (result) {
       size_t bufferSize;
@@ -910,15 +909,12 @@ _swift_backtrace_demangle(const char *mangledName,
 
       free(result);
 
-      *status = 0;
       return outputBuffer;
     }
 #else
     // On Windows, the mangling is different.
     // ###TODO: Call __unDName()
 #endif
-  } else {
-    *status = -2;
   }
 
   return nullptr;