windows下创建共享内存

[Muaji]

用CreateFileMapping创建
在网上看到说共享内存块的名字要加"Global\\",否则会使共享的内存只能在当前用户下被另一个或多个进程访问。
可是我在创建共享内存如下

创建失败，返回的句柄为NULL

然后我改成这样

初次调试成功了，然后我给使用者用，在他们机器上调试，又返回NULL了。

有没有可能是电脑系统的问题还是什么原因？名字究竟是该取"Global\\share"还是"Global\\\\share"
会是什么情况创建失败？

[赵4老师]

lpName The name of the file mapping object. If this parameter matches the name of an existing mapping object, the function requests access to the object with the protection that flProtect specifies. If this parameter is NULL, the file mapping object is created without a name. If lpName matches the name of an existing event, semaphore, mutex, waitable timer, or job object, the function fails, and the GetLastError function returns ERROR_INVALID_HANDLE. This occurs because these objects share the same namespace. Terminal Services: The name can have a "Global\" or "Local\" prefix to explicitly create the object in the global or session namespace. The remainder of the name can contain any character except the backslash character (\). Creating a file mapping object in the global namespace requires the SeCreateGlobalPrivilege privilege. For more information, see Kernel Object Namespaces. Windows XP: Fast user switching is implemented by using Terminal Services sessions. The first user to log on uses session 0 (zero), the next user to log on uses session 1 (one), and so on. Kernel object names must follow the guidelines that are outlined for Terminal Services so that applications can support multiple users. Windows 2000: If Terminal Services is not running, the "Global\" and "Local\" prefixes are ignored. The remainder of the name can contain any character except the backslash character.

[赵4老师]

C++ Character Constants Character constants are one or more members of the “source character set,” the character set in which a program is written, surrounded by single quotation marks ('). They are used to represent characters in the “execution character set,” the character set on the machine where the program executes. Microsoft Specific For Microsoft C++, the source and execution character sets are both ASCII. END Microsoft Specific There are three kinds of character constants: Normal character constants Multicharacter constants Wide-character constants Note Use wide-character constants in place of multicharacter constants to ensure portability. Character constants are specified as one or more characters enclosed in single quotation marks. For example: char ch = 'x'; // Specify normal character constant. int mbch = 'ab'; // Specify system-dependent // multicharacter constant. wchar_t wcch = L'ab'; // Specify wide-character constant. Note that mbch is of type int. If it were declared as type char, the second byte would not be retained. A multicharacter constant has four meaningful characters; specifying more than four generates an error message. Syntax character-constant : 'c-char-sequence' L'c-char-sequence' c-char-sequence : c-char c-char-sequence c-char c-char : any member of the source character set except the single quotation mark ('), backslash (\), or newline character escape-sequence escape-sequence : simple-escape-sequence octal-escape-sequence hexadecimal-escape-sequence simple-escape-sequence : one of \' \" \? \\ \a \b \f \n \r \t \v octal-escape-sequence : \octal-digit \octal-digit octal-digit \octal-digit octal-digit octal-digit hexadecimal-escape-sequence : \xhexadecimal-digit hexadecimal-escape-sequence hexadecimal-digit Microsoft C++ supports normal, multicharacter, and wide-character constants. Use wide-character constants to specify members of the extended execution character set (for example, to support an international application). Normal character constants have type char, multicharacter constants have type int, and wide-character constants have type wchar_t. (The type wchar_t is defined in the standard include files STDDEF.H, STDLIB.H, and STRING.H. The wide-character functions, however, are prototyped only in STDLIB.H.) The only difference in specification between normal and wide-character constants is that wide-character constants are preceded by the letter L. For example: char schar = 'x'; // Normal character constant wchar_t wchar = L'\x81\x19'; // Wide-character constant Table 1.2 shows reserved or nongraphic characters that are system dependent or not allowed within character constants. These characters should be represented with escape sequences. Table 1.2 C++ Reserved or Nongraphic Characters Character ASCII Representation ASCII Value Escape Sequence Newline NL (LF) 10 or 0x0a \n Horizontal tab HT 9 \t Vertical tab VT 11 or 0x0b \v Backspace BS 8 \b Carriage return CR 13 or 0x0d \r Formfeed FF 12 or 0x0c \f Alert BEL 7 \a Backslash \ 92 or 0x5c \\ Question mark ? 63 or 0x3f \? Single quotation mark ' 39 or 0x27 \' Double quotation mark " 34 or 0x22 \" Octal number ooo — \ooo Hexadecimal number hhh — \xhhh Null character NUL 0 \0 If the character following the backslash does not specify a legal escape sequence, the result is implementation defined. In Microsoft C++, the character following the backslash is taken literally, as though the escape were not present, and a level 1 warning (“unrecognized character escape sequence”) is issued. Octal escape sequences, specified in the form \ooo, consist of a backslash and one, two, or three octal characters. Hexadecimal escape sequences, specified in the form \xhhh, consist of the characters \x followed by a sequence of hexadecimal digits. Unlike octal escape constants, there is no limit on the number of hexadecimal digits in an escape sequence. Octal escape sequences are terminated by the first character that is not an octal digit, or when three characters are seen. For example: wchar_t och = L'\076a'; // Sequence terminates at a char ch = '\233'; // Sequence terminates after 3 characters Similarly, hexadecimal escape sequences terminate at the first character that is not a hexadecimal digit. Because hexadecimal digits include the letters a through f (and A through F), make sure the escape sequence terminates at the intended digit. Because the single quotation mark (') encloses character constants, use the escape sequence \' to represent enclosed single quotation marks. The double quotation mark (") can be represented without an escape sequence. The backslash character (\) is a line-continuation character when placed at the end of a line. If you want a backslash character to appear within a character constant, you must type two backslashes in a row (\\). (SeePhases of Translation in the Preprocessor Reference for more information about line continuation.)

[jiht594]

如果失败了, 用GetLastError函数看一下是什么错误