使用CreateProcess和wcscat_s容易出错的地方

由于没有仔细阅读MSDN，导致使用函数CreateProcess和wcscat_s出错，简单的问题，耽误不少时间。

1. CreateProcess的第二个参数不能指向只读的一段内存空间。

2. errno_t wcscat_s( wchar_t *strDestination, size_t numberOfElements, const wchar_t *strSource )的第二个参数是strDestination buffer的size(Size of the destination string buffer)，而不是连接字符串的size。

CreateProcess Function

Creates a new process and its primary thread. The new process runs in the security context of the calling process.

If the calling process is impersonating another user, the new process uses the token for the calling process, not the impersonation token. To run the new process in the security context of the user represented by the impersonation token, use the CreateProcessAsUser or CreateProcessWithLogonW function.

BOOL WINAPI CreateProcess(
  __in          LPCTSTR lpApplicationName,
  __in_out      LPTSTR lpCommandLine,
  __in          LPSECURITY_ATTRIBUTES lpProcessAttributes,
  __in          LPSECURITY_ATTRIBUTES lpThreadAttributes,
  __in          BOOL bInheritHandles,
  __in          DWORD dwCreationFlags,
  __in          LPVOID lpEnvironment,
  __in          LPCTSTR lpCurrentDirectory,
  __in          LPSTARTUPINFO lpStartupInfo,
  __out         LPPROCESS_INFORMATION lpProcessInformation
);

Parameters

lpApplicationName

The name of the module to be executed. This module can be a Windows-based application. It can be some other type of module (for example, MS-DOS or OS/2) if the appropriate subsystem is available on the local computer.

The string can specify the full path and file name of the module to execute or it can specify a partial name. In the case of a partial name, the function uses the current drive and current directory to complete the specification. The function will not use the search path. If the file name does not contain an extension, .exe is assumed. Therefore, if the file name extension is .com, this parameter must include the .com extension.

The lpApplicationName parameter can be NULL. In that case, the module name must be the first white space-delimited token in the lpCommandLine string. If you are using a long file name that contains a space, use quoted strings to indicate where the file name ends and the arguments begin; otherwise, the file name is ambiguous. For example, consider the string "c:\program files\sub dir\program name". This string can be interpreted in a number of ways. The system tries to interpret the possibilities in the following order:

c:\program.exe files\sub dir\program name

c:\program files\sub.exe dir\program name

c:\program files\sub dir\program.exe name

c:\program files\sub dir\program name.exe

If the executable module is a 16-bit application, lpApplicationName should be NULL, and the string pointed to by lpCommandLine should specify the executable module as well as its arguments.

To run a batch file, you must start the command interpreter; set lpApplicationName to cmd.exe and set lpCommandLine to the name of the batch file.

lpCommandLine

The command line to be executed. The maximum length of this string is 32K characters. If lpApplicationName is NULL, the module name portion of lpCommandLine is limited to MAX_PATH characters.

The Unicode version of this function, CreateProcessW, can modify the contents of this string. Therefore, this parameter cannot be a pointer to read-only memory (such as a const variable or a literal string). If this parameter is a constant string, the function may cause an access violation.

The lpCommandLine parameter can be NULL. In that case, the function uses the string pointed to by lpApplicationName as the command line.

If both lpApplicationName and lpCommandLine are non-NULL, the null-terminated string pointed to by lpApplicationName specifies the module to execute, and the null-terminated string pointed to by lpCommandLine specifies the command line. The new process can use GetCommandLine to retrieve the entire command line. Console processes written in C can use the argc and argv arguments to parse the command line. Because argv[0] is the module name, C programmers generally repeat the module name as the first token in the command line.

If lpApplicationName is NULL, the first white-space – delimited token of the command line specifies the module name. If you are using a long file name that contains a space, use quoted strings to indicate where the file name ends and the arguments begin (see the explanation for the lpApplicationName parameter). If the file name does not contain an extension, .exe is appended. Therefore, if the file name extension is .com, this parameter must include the .com extension. If the file name ends in a period (.) with no extension, or if the file name contains a path, .exe is not appended. If the file name does not contain a directory path, the system searches for the executable file in the following sequence:

1. The directory from which the application loaded.
2. The current directory for the parent process.
3. The 32-bit Windows system directory. Use the GetSystemDirectory function to get the path of this directory.

   Windows Me/98/95:  The Windows system directory. Use the GetSystemDirectory function to get the path of this directory.

4. The 16-bit Windows system directory. There is no function that obtains the path of this directory, but it is searched. The name of this directory is System.
5. The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
6. The directories that are listed in the PATH environment variable. Note that this function does not search the per-application path specified by the App Paths registry key. To include this per-application path in the search sequence, use the ShellExecute function.

The system adds a null character to the command line string to separate the file name from the arguments. This divides the original string into two strings for internal processing.

lpProcessAttributes

A pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpProcessAttributes is NULL, the handle cannot be inherited.

The lpSecurityDescriptor member of the structure specifies a security descriptor for the new process. If lpProcessAttributes is NULL or lpSecurityDescriptor is NULL, the process gets a default security descriptor. The ACLs in the default security descriptor for a process come from the primary token of the creator.

Windows XP/2000/NT:  The ACLs in the default security descriptor for a process come from the primary or impersonation token of the creator. This behavior changed with Windows XP SP2 and Windows Server 2003.

lpThreadAttributes

A pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpThreadAttributes is NULL, the handle cannot be inherited.

The lpSecurityDescriptor member of the structure specifies a security descriptor for the main thread. If lpThreadAttributes is NULL or lpSecurityDescriptor is NULL, the thread gets a default security descriptor. The ACLs in the default security descriptor for a thread come from the process token.

Windows XP/2000/NT:  The ACLs in the default security descriptor for a thread come from the primary or impersonation token of the creator. This behavior changed with Windows XP SP2 and Windows Server 2003.

bInheritHandles

If this parameter TRUE, each inheritable handle in the calling process is inherited by the new process. If the parameter is FALSE, the handles are not inherited. Note that inherited handles have the same value and access rights as the original handles.

dwCreationFlags

The flags that control the priority class and the creation of the process. For a list of values, see Process Creation Flags.

This parameter also controls the new process's priority class, which is used to determine the scheduling priorities of the process's threads. For a list of values, see GetPriorityClass. If none of the priority class flags is specified, the priority class defaults to NORMAL_PRIORITY_CLASS unless the priority class of the creating process is IDLE_PRIORITY_CLASS or BELOW_NORMAL_PRIORITY_CLASS. In this case, the child process receives the default priority class of the calling process.

lpEnvironment

A pointer to the environment block for the new process. If this parameter is NULL, the new process uses the environment of the calling process.

An environment block consists of a null-terminated block of null-terminated strings. Each string is in the following form:

name=value\0

Because the equal sign is used as a separator, it must not be used in the name of an environment variable.

An environment block can contain either Unicode or ANSI characters. If the environment block pointed to by lpEnvironment contains Unicode characters, be sure that dwCreationFlags includes CREATE_UNICODE_ENVIRONMENT. If this parameter is NULL and the environment block of the parent process contains Unicode characters, you must also ensure that dwCreationFlags includes CREATE_UNICODE_ENVIRONMENT.

The ANSI version of this function, CreateProcessA fails if the total size of the environment block for the process exceeds 32,767 characters.

Note that an ANSI environment block is terminated by two zero bytes: one for the last string, one more to terminate the block. A Unicode environment block is terminated by four zero bytes: two for the last string, two more to terminate the block.

lpCurrentDirectory

The full path to the current directory for the process. The string can also specify a UNC path.

If this parameter is NULL, the new process will have the same current drive and directory as the calling process. (This feature is provided primarily for shells that need to start an application and specify its initial drive and working directory.)

lpStartupInfo

A pointer to a STARTUPINFO or STARTUPINFOEX structure.

To set extended attributes, use a STARTUPINFOEX structure and specify EXTENDED_STARTUPINFO_PRESENT in the dwCreationFlags parameter.

lpProcessInformation

A pointer to a PROCESS_INFORMATION structure that receives identification information about the new process.

Handles in PROCESS_INFORMATION must be closed with CloseHandle when they are no longer needed.

Return Value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.