Merge pull request #285 from mwinterb/winerror_winu

Changed format_windows_error to not need LocalFree

cppformat/format.cc

@@ -588,27 +588,25 @@ FMT_FUNC void fmt::WindowsError::init(
 FMT_FUNC void fmt::internal::format_windows_error(
     fmt::Writer &out, int error_code,
     fmt::StringRef message) FMT_NOEXCEPT {
-  class String {
-   private:
-    LPWSTR str_;
-
-   public:
-    String() : str_() {}
-    ~String() { LocalFree(str_); }
-    LPWSTR *ptr() { return &str_; }
-    LPCWSTR c_str() const { return str_; }
-  };
   FMT_TRY {
-    String system_message;
-    if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
-        FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0,
-        error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
-        reinterpret_cast<LPWSTR>(system_message.ptr()), 0, 0)) {
-      UTF16ToUTF8 utf8_message;
-      if (utf8_message.convert(system_message.c_str()) == ERROR_SUCCESS) {
-        out << message << ": " << utf8_message;
-        return;
+    MemoryBuffer<wchar_t, INLINE_BUFFER_SIZE> buffer;
+    buffer.resize(INLINE_BUFFER_SIZE);
+    for (;;) {
+      wchar_t *system_message = &buffer[0];
+      int result = FormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                                  0, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                                  system_message, static_cast<uint32_t>(buffer.size()), 0);
+      if (result != 0) {
+        UTF16ToUTF8 utf8_message;
+        if (utf8_message.convert(system_message) == ERROR_SUCCESS) {
+          out << message << ": " << utf8_message;
+          return;
+        }
+        break;
       }
+      if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+        break;  // Can't get error message, report error code instead.
+      buffer.resize(buffer.size() * 2);
     }
   } FMT_CATCH(...) {}
   fmt::format_error_code(out, error_code, message);  // 'fmt::' is for bcc32.

test/util-test.cc

@@ -873,6 +873,27 @@ TEST(UtilTest, FormatWindowsError) {
   EXPECT_EQ(fmt::format("error {}", ERROR_FILE_EXISTS), actual_message.str());
 }
 
+TEST(UtilTest, FormatLongWindowsError) {
+  LPWSTR message = 0;
+  // this error code is not available on all Windows platforms and
+  // Windows SDKs, so do not fail the test if the error string cannot
+  // be retrieved.
+  const int provisioning_not_allowed = 0x80284013L /*TBS_E_PROVISIONING_NOT_ALLOWED*/;
+  if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+      FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0,
+      provisioning_not_allowed, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+      reinterpret_cast<LPWSTR>(&message), 0, 0) == 0) {
+    return;
+  }
+  fmt::internal::UTF16ToUTF8 utf8_message(message);
+  LocalFree(message);
+  fmt::MemoryWriter actual_message;
+  fmt::internal::format_windows_error(
+      actual_message, provisioning_not_allowed, "test");
+  EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
+      actual_message.str());
+}
+
 TEST(UtilTest, WindowsError) {
   check_throw_error<fmt::WindowsError>(
       ERROR_FILE_EXISTS, fmt::internal::format_windows_error);