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PathAllocCombine function (pathcch.h)

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Concatenates two path fragments into a single path. This function also canonicalizes any relative path elements, replacing path elements such as "." and "..".

This function differs from PathCchCombine and PathCchCombineEx in that it returns the result on the heap. This means that the caller does not have to declare the size of the returned string and reduces stack use.

This function differs from PathCombine in that it accepts paths with "\", "\?" and "\?\UNC" prefixes.

Note This function, PathCchCombine, or PathCchCombineEx, should be used in place of PathCombine.
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Syntax

WINPATHCCHAPI HRESULT PathAllocCombine(
  [in]  PCWSTR pszPathIn,
  [in]  PCWSTR pszMore,
  [in]  ULONG  dwFlags,
  [out] PWSTR  *ppszPathOut
);

Parameters

[in] pszPathIn

A pointer to the first path string.

[in] pszMore

A pointer to the second path string. If this path begins with a single backslash, it is combined with only the root of the path pointed to by pszPathIn. If this path is fully qualified, it is copied directly to the output buffer without being combined with the other path.

[in] dwFlags

One or more of the following flags:

Value Meaning
PATHCCH_NONE
0x0000000
 Do not allow for the construction of \\?\ paths (ie, long paths) longer than MAX_PATH .
PATHCCH_ALLOW_LONG_PATHS
0x00000001
 Allow the construction of \\?\ paths longer than MAX_PATH .
PATHCCH_FORCE_ENABLE_LONG_NAME_PROCESS
0x00000002
 Forces the API to treat the caller as long path enabled, independent of the process's long name enabled state. This option can be used only when PATHCCH_ALLOW_LONG_PATHS is specified, and cannot be used with PATHCCH_FORCE_DISABLE_LONG_NAME_PROCESS.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_FORCE_DISABLE_LONG_NAME_PROCESS
0x00000004
 Forces the API to treat the caller as long path disabled, independent of the process's long name enabled state. This option can be used only when PATHCCH_ALLOW_LONG_PATHS is specified, and cannot be used with PATHCCH_FORCE_ENABLE_LONG_NAME_PROCESS.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_DO_NOT_NORMALIZE_SEGMENTS
0x00000008
 Disables the normalization of path segments that includes removing trailing dots and spaces. This enables access to paths that win32 path normalization will block.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_ENSURE_IS_EXTENDED_LENGTH_PATH
0x00000010
 Converts the input path into the extended length DOS device path form (with the \\?\ prefix) if not already in that form. This enables access to paths that are otherwise not addressable due to Win32 normalization rules (that can strip trailing dots and spaces) and path length limitations. This option implies the same behavior of PATHCCH_DO_NOT_NORMALIZE_SEGMENTS.

Note This value is available starting in Windows 10, version 1703.
PATHCCH_ENSURE_TRAILING_SLASH
0x00000020
 When combining or normalizing a path, ensure there is a trailing backslash.

Note This value is available starting in Windows 10, version 1703.

[out] ppszPathOut

The address of a pointer to a buffer that, when this function returns successfully, receives the combined path string. It is the responsibility of the caller to free this resource, when it is no longer needed, by calling the LocalFree function. This value cannot be NULL.

Return value

If this function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

While either pszPathIn or pszMore can NULL, they cannot both be NULL.

This function supports these alternate path forms:

  • \\?\
  • \\?\\UNC\
  • \\?\Volume{guid}\

Requirements

Requirement Value
Minimum supported client Windows 8 [desktop apps | UWP apps]
Minimum supported server Windows Server 2012 [desktop apps | UWP apps]
Target Platform Windows
Header pathcch.h
Library Pathcch.lib

See also

PathCchCombine

PathCchCombineEx