Structured Text - Saving memory address of a variable as string

Hi,


For strictly development purposes I would like to save the memory address of a variable as a string (e.g. "16#FFFFFFFF"). Now, specifically it is the address of an interface that I want to get the address of, and I have tried the following:



But neither lets me compile, due to the error "cannot convert type 'POINTER TO I_StatusInterface' to type 'STRING' / 'DWORD''

Using TwinCAT, if that matters.

I think the problem is with the DWORD_TO conversion as the data type for a pointer is technically a dword but isn't explicitly defined as one. Try the TO conversion for instances where the input data type isn't explicitly given. I've never tried this but it might do the trick.

Cheers



Operator ‘TO_<xxx>’¶

TO_<data type>

The function depends on what is described for each typed conversion.


Examples

ST implementation language:


VAR
iVar : INT;
bVar : BOOL;
sVar : STRING;
rVar : REAL;
END_VAR

iVar := TO_INT(4.22); (* Result: 4 *)
bVar := TO_BOOL(1); (* Result: TRUE *)
sVar := TO_STRING(342); (* Result: '342' *)
rVar := TO_WORD('123'); (* Result: 123 *)

Use an intermediate dword to get over the type conversions:

L D[AR2 said:

Use an intermediate dword to get over the type conversions:

Code:

dwAddress:=ADR(pTable);
myString:=DWORD_TO_STRING(dwAddress);

Click to expand...

This does not work in TwinCAT, and fails at the line "dwAddress:=ADR(pTable)". VisualStudio reports upon attempting to build:





Kvogel's solution seems to work though, with the following code:





Thank you both.

The target system is crucial for pointers etc, I used TwinCat3 for an x86 target for the previously posted code which compiled ok - is your target x64?, if so the intermediate variable needs to LWORD and the string conversion LWORD_TO_STRING

L D[AR2 said:

The target system is crucial for pointers etc, I used TwinCat3 for an x86 target for the previously posted code which compiled ok - is your target x64?, if so the intermediate variable needs to LWORD and the string conversion LWORD_TO_STRING

Code:

lwAddress:=ADR(pTable);
myString:=LWORD_TO_STRING(lwAddress);

Click to expand...

You are completely right, I should have included the fact that the target system was a 64 bit architecture in the first post. Your code compiles and works without problem, and LWORD is of course the correct datatype in my case.



... Kind of scary that it ran fine with the DWORD (32 bit) casting though, there would be a lot of information loss in such a conversion.