From c97c4dbeacec95ee6799126cb8cca721b71b7e8f Mon Sep 17 00:00:00 2001
From: Sandy Carter <bwrsandman@gmail.com>
Date: Sun, 27 Jan 2019 10:10:04 -0500
Subject: [PATCH] [string] Remove reuse of va_list in AppendVarargs

va_list are not guarenteed to maintain their values after being used.
With clang on Linux, args is undefined after fetching length and will print
"(null)".
Copy args into another va_list before getting length to prevent this.
Add tests.
---
 src/xenia/base/string_buffer.cc       |  5 ++++-
 src/xenia/base/testing/string_test.cc | 13 +++++++++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/xenia/base/string_buffer.cc b/src/xenia/base/string_buffer.cc
index f7b4c8889..ac8a924d6 100644
--- a/src/xenia/base/string_buffer.cc
+++ b/src/xenia/base/string_buffer.cc
@@ -64,7 +64,10 @@ void StringBuffer::AppendFormat(const char* format, ...) {
 }
 
 void StringBuffer::AppendVarargs(const char* format, va_list args) {
-  int length = vsnprintf(nullptr, 0, format, args);
+  va_list size_args;
+  va_copy(size_args, args);  // arg is indeterminate after the return so copy it
+  int length = vsnprintf(nullptr, 0, format, size_args);
+  va_end(size_args);
   Grow(length + 1);
   vsnprintf(buffer_ + buffer_offset_, buffer_capacity_, format, args);
   buffer_offset_ += length;
diff --git a/src/xenia/base/testing/string_test.cc b/src/xenia/base/testing/string_test.cc
index 1f287d933..946ed59b2 100644
--- a/src/xenia/base/testing/string_test.cc
+++ b/src/xenia/base/testing/string_test.cc
@@ -8,6 +8,7 @@
 */
 
 #include "xenia/base/string.h"
+#include "xenia/base/string_buffer.h"
 
 #include "third_party/catch/include/catch.hpp"
 
@@ -16,8 +17,16 @@ namespace base {
 namespace test {
 
 TEST_CASE("StringBuffer") {
-  // TODO(bwrsandman):
-  REQUIRE(false);
+  StringBuffer sb;
+  uint32_t module_flags = 0x1000000;
+
+  std::string path_(R"(\Device\Cdrom0\default.xex)");
+  sb.AppendFormat("Module %s:\n", path_.c_str());
+  REQUIRE(sb.to_string() == "Module \\Device\\Cdrom0\\default.xex:\n");
+  sb.AppendFormat("    Module Flags: %.8X\n", module_flags);
+  REQUIRE(
+      sb.to_string() ==
+      "Module \\Device\\Cdrom0\\default.xex:\n    Module Flags: 01000000\n");
 }
 
 }  // namespace test