PRB: Cannot Use SysAllocStr() to Create BSTRs; L"String" (194756)
The information in this article applies to:
- Microsoft Platform Software Development Kit (SDK) 1.0
This article was previously published under Q194756 SYMPTOMS
A value of type L"String" passed as a BSTR value does not function
correctly.
CAUSE
BSTR values are Unicode strings with a length prefix where the length is
the number of bytes, excluding the terminating wide NULL. For example, the
word "Hello" represented as a BSTR is the following:
UINT(10) followed by UNICODE(Hello) - "\x0A\0\0\0H\0e\0l\0l\0o\0\0\0"
If you use a plain L"String" value instead of a proper BSTR value, the BSTR
length function SysStringLen() treats the value preceding the text
(typically random values from the stack) as the byte count and uses half
that value as the length.
RESOLUTION
Use the SysAllocString() function to get a proper BSTR value. The allocated
string must be released later by calling SysFreeString(). Please note that
you should not add the length prefix because the format of the BSTR is
subject to change. Following is some sample code that illustrates this
solution:
BSTR pTempStr = SysAllocString(L"Test");
[insert code to use pTempStr here as needed]
SysFreeString(pTempStr);
REFERENCES
Microsoft Active Accessibility SDK
| Modification Type: | Minor | Last Reviewed: | 7/11/2005 |
|---|
| Keywords: | kbAAcc kbprb KB194756 |
|---|
|