强制价值bool（业绩警告） [英] Forcing value to bool (performance warning)
问题描述
在下面的代码中，所有以PPTfile开头的行<<在构建时出现以下错误。
" // i：\ C ++ \ C ++ Code\FileOperations\Form1 .h（127）：警告C4800：
''System :: String __gc *''：强制值为bool''true''或''false''
（性能警告）
我得到以下输出，这显然是错误的：
进程ID = 0x1
ref count（c）= 0x1
线程数= 1
父进程ID = 0x1
优先级基数= 1
进程ID = 0x1
引用计数（c）= 0x1
线程数= 1
进程ID = 0x1
优先基数= 1
1
1
1
1
1
------------------------------------ -------------
DWORD x = 23;
LONG aa = 16;
字符串* buf;
ofstream PPTfile（" PPT.txt"，ios :: out）;
PPTfile<< "进程ID = 0x << x.ToString（" X8"）<< endl;
PPTfile<< " ref count（c）= 0x << x.ToString（" X4"）<< endl;
PPTfile<< "线程数= << x.ToString（）<< endl;
PPTfile<< "父进程ID = 0x << x.ToString（" X8"）<< endl;
PPTfile<< "优先基数= << aa.ToString（）<< endl;
buf = x.ToString（" X8"）;
PPTfile<< "进程ID = 0x << buf<< endl;
buf = x.ToString（" X4"）;
PPTfile<< " ref count（c）= 0x << buf<< endl;
buf = x.ToString（）;
PPTfile<< "线程数= << buf<< endl;
buf = x.ToString（" X8"）;
PPTfile<< "进程ID = 0x << buf<< endl;
buf = aa.ToString（）;
PPTfile<< "优先基数= << buf<< endl;
buf = String :: Concat（S" Process ID = 0x"，x.ToString（" X8"））;
PPTfile< ;< buf<< endl;
buf = String :: Concat（S" ref count（c）= 0x"，x.ToString（" X4"））;
PPTfile< < buf<< endl;
buf = String :: Concat（S" Thread Count ="，x.ToString（））;
PPTfile<< buf<< endl;
buf = String :: Concat（S" parent process ID = 0x"，x.ToString（" X8"））;
PPTfile<< buf<< endl;
buf = String :: Concat（S" Priority Base ="，aa.ToString（））;
PPTfile<< buf<< endl;
PPTfile.close（）;
Howard Kaikow写道：In下面的代码，所有以PPTfile开头的行<<在构建时收到以下错误。
" // i：\ C ++ \ C ++ Code \ FileOperations\Form1.h（127）：警告C4800 ：''System :: String __gc *''：强制值为bool''true''或''false''
（性能警告）
我得到以下输出，这显然是错误的：
ToString返回一个.NET对象句柄，本机C ++无法处理，
因此它试图将其隐式转换为bool。因此
警告。您必须使用以下函数（作为示例）
将托管字符串转换为非托管字符串：
std :: wstring ToUnmanagedString（System :: String * str）
{
const wchar_t __pin * c_str = PtrToStringChars（str）;
return std :: wstring（c_str）;
}
另外，你不应该使用endl，你应该使用\ n代替。 endl
刷新流，这是一个严重的性能损失。
Tom
Thanx。
-
http://www.standards.com/; 请参阅Howard Kaikow的网站。
" Tamas Demjen" < TD ***** @ yahoo.com>在消息中写道
新闻：ej ************** @ tk2msftngp13.phx.gbl ...Howard Kaikow写道：< blockquote class =post_quotes>在下面的代码中，所有以PPTfile开头的行<<在构建时获得
以下错误。
" // i：\ C ++ \ C ++ Code\FileOperations\Form1.h（127）：警告C4800 ：''System :: String __gc *''：强制值为bool''true''或''false''
（性能警告）
我得到以下输出，这显然是错误的：
ToString返回一个.NET对象句柄，本机C ++无法处理，
因此它尝试转换它含蓄地bool。因此
警告。您必须使用以下函数（作为示例）将托管字符串转换为非托管字符串：
std :: wstring ToUnmanagedString（System :: String * str）
{
const wchar_t __pin * c_str = PtrToStringChars（str）;
返回std :: wstring（c_str）;
}
另外，你不应该使用endl，你应该使用\ n代替。 endl
刷新流，这是一个严重的性能损失。
Tom
" Tamas Demjen" < TD ***** @ yahoo.com>在消息中写道
news：ej ************** @ tk2msftngp13.phx.gbl ...ToString返回一个.NET对象句柄，本机C ++无法处理，因此它试图将其隐式转换为bool。因此
警告。您必须使用以下函数（作为示例）将托管字符串转换为非托管字符串：
std :: wstring ToUnmanagedString（System :: String * str）
{
const wchar_t __pin * c_str = PtrToStringChars（str）;
返回std :: wstring（c_str）;
}
使用以上，我得到了错误：
i：\ C ++ \ C ++ Code\FileOperations\Form1.h（101）：错误C2230：''ToUnmanagedString''
：托管类的成员函数不能返回非托管类或
struct''std :: basic_string< _Elem，_Traits，_Ax>''除非它是一个总计
，含
[
_Elem = wchar_t，
_Traits = std :: char_traits< wchar_t> ，
_Ax = std :: allocator< wchar_t>
]
这是什么意思？
In the code below, ALL the lines that start with PPTfile << are getting the
following error at build time.
"//i:\C++\C++Code\FileOperations\Form1.h(127) : warning C4800:
''System::String __gc *'' : forcing value to bool ''true'' or ''false''
(performance warning)"
I get the following output, which is obviously wrong:
Process ID = 0x1
ref count (c) = 0x1
Thread Count = 1
parent process ID = 0x1
Priority Base = 1
Process ID = 0x1
ref count (c) = 0x1
Thread Count = 1
Process ID = 0x1
Priority Base = 1
1
1
1
1
1
-------------------------------------------------
DWORD x = 23;
LONG aa = 16;
String *buf;
ofstream PPTfile("PPT.txt", ios::out);
PPTfile << " Process ID = 0x" << x.ToString("X8") << endl;
PPTfile << " ref count (c) = 0x" << x.ToString("X4") << endl;
PPTfile << " Thread Count = " << x.ToString() << endl;
PPTfile << " parent process ID = 0x" << x.ToString("X8") << endl;
PPTfile << " Priority Base = " << aa.ToString() << endl;
buf = x.ToString("X8");
PPTfile << " Process ID = 0x" << buf << endl;
buf = x.ToString("X4");
PPTfile << " ref count (c) = 0x" << buf << endl;
buf = x.ToString();
PPTfile << " Thread Count = " << buf << endl;
buf = x.ToString("X8");
PPTfile << " Process ID = 0x" << buf << endl;
buf = aa.ToString();
PPTfile << " Priority Base = " << buf << endl;
buf = String::Concat(S" Process ID = 0x", x.ToString("X8"));
PPTfile << buf << endl;
buf = String::Concat(S" ref count (c) = 0x", x.ToString("X4"));
PPTfile << buf << endl;
buf=String::Concat(S" Thread Count = ", x.ToString());
PPTfile << buf << endl;
buf=String::Concat(S" parent process ID = 0x", x.ToString("X8"));
PPTfile << buf << endl;
buf =String::Concat(S" Priority Base = ", aa.ToString());
PPTfile << buf << endl;
PPTfile.close();
Howard Kaikow wrote:In the code below, ALL the lines that start with PPTfile << are getting the
following error at build time.
"//i:\C++\C++Code\FileOperations\Form1.h(127) : warning C4800:
''System::String __gc *'' : forcing value to bool ''true'' or ''false''
(performance warning)"
I get the following output, which is obviously wrong:
ToString returns a .NET object handle, which native C++ can''t handle,
and therefore it tries to convert it implicitly to bool. Thus the
warning. You have to use the following function (as an example) to
convert managed strings to unmanaged ones:
std::wstring ToUnmanagedString(System::String* str)
{
const wchar_t __pin* c_str = PtrToStringChars(str);
return std::wstring(c_str);
}
In addition, you shouldn''t use endl, you should use "\n" instead. endl
flushes the stream, which is a serious performance penalty.
Tom
Thanx.
--
http://www.standards.com/; See Howard Kaikow''s web site.
"Tamas Demjen" <td*****@yahoo.com> wrote in message
news:ej**************@tk2msftngp13.phx.gbl...Howard Kaikow wrote:In the code below, ALL the lines that start with PPTfile << are getting the following error at build time.
"//i:\C++\C++Code\FileOperations\Form1.h(127) : warning C4800:
''System::String __gc *'' : forcing value to bool ''true'' or ''false''
(performance warning)"
I get the following output, which is obviously wrong:
ToString returns a .NET object handle, which native C++ can''t handle,
and therefore it tries to convert it implicitly to bool. Thus the
warning. You have to use the following function (as an example) to
convert managed strings to unmanaged ones:
std::wstring ToUnmanagedString(System::String* str)
{
const wchar_t __pin* c_str = PtrToStringChars(str);
return std::wstring(c_str);
}
In addition, you shouldn''t use endl, you should use "\n" instead. endl
flushes the stream, which is a serious performance penalty.
Tom
"Tamas Demjen" <td*****@yahoo.com> wrote in message
news:ej**************@tk2msftngp13.phx.gbl...ToString returns a .NET object handle, which native C++ can''t handle,
and therefore it tries to convert it implicitly to bool. Thus the
warning. You have to use the following function (as an example) to
convert managed strings to unmanaged ones:
std::wstring ToUnmanagedString(System::String* str)
{
const wchar_t __pin* c_str = PtrToStringChars(str);
return std::wstring(c_str);
}
Using the above, I got the error:
i:\C++\C++Code\FileOperations\Form1.h(101): error C2230: ''ToUnmanagedString''
: a member function of a managed class cannot return a non-managed class or
struct ''std::basic_string<_Elem,_Traits,_Ax>'' unless it is an aggregate
with
[
_Elem=wchar_t,
_Traits=std::char_traits<wchar_t>,
_Ax=std::allocator<wchar_t>
]
What does that mean?
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