Returns the current memory address of a string.
Address := StrPtr(Value)
Type: String
Type: Integer
This function returns the current memory address of Value.
The lifetime of an address and which operations are valid to perform on it depend on how Value was passed to this function. There are three distinct cases, shown as example code below. In all cases, if the string will not be modified, the return value can be passed directly to a DllCall function or SendMessage.
Ptr := StrPtr(MyVar)
If Value is a variable reference such as MyVar (and not a built-in variable), the return value is the memory address of the variable's internal string buffer. VarSetStrCapacity(&MyVar) returns the size of the buffer in characters, excluding the terminating null character.
The address should be considered valid only until the variable is freed or has been reassigned by means of any of the assignment operators or by passing it to a built-in function. The address of the contents of a function's local variable is not valid after the function returns, as local variables are freed automatically.
The address can be stored in a structure or another variable, and passed indirectly to DllCall or SendMessage or used in other ways, for as long as it remains valid as described above.
The script may change the value of the string indirectly by passing the address to NumPut, DllCall or SendMessage. If the length of the string is changed this way, the variable's internal length property must be updated by calling VarSetStrCapacity(&MyVar, -1).
Ptr := StrPtr("literal string")
The address of a literal string is valid until the program exits. The script should not attempt to modify the string. The address can be stored in a structure or another variable, and passed indirectly to DllCall or SendMessage or used in other ways.
SendMessage 0x000C, 0, StrPtr(A_ScriptName " changed this title"),, "A"
The address of a temporary string is valid only until evaluation of the overall expression or function call statement is completed, after which time it must not be used. For the example above, the address is valid until SendMessage returns. All of the following yield temporary strings:
If not explicitly covered above, it is safe to assume the string is temporary.
VarSetStrCapacity, DllCall, SendMessage, Buffer object, NumPut, NumGet