how to fix migratation error in vs2019

Question

how to fix migratation error in vs2019

Lakshay Goel 10

Hi team ,

i am trying to fix a migratation error

" Error C2039 '_ptr': is not a member of '_iobuf'"

error comes while migrartion of the code ,please help me out in this

Viorel 122.6K Reputation points

2023-02-16T18:37:55.91+00:00

It seems that the code uses some undocumented unrecommended internal variables. Show some details. Maybe the code can be normalised.
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-02-17T02:40:15.14+00:00

Could you provide a minimal reproducible example?

Lakshay Goel 10

@Minxin Yu

@Viorel

link-https://stackoverflow.com/questions/44018520/porting-issue-in-visual-studio-2015-flag-is-not-a-member-of-iobuf

#include "iostream"
using namespace std;
#define mybuffer(param)       ((param)->_flag & (_IOMYBUF))

int main()
{
    mybuffer(stderr); // I don't understand what is the purpose of this line.
                      // So, facing issue in replacing this code statement.
    return 0;
}

Lakshay Goel 10 Reputation points

2023-02-18T13:49:29.2066667+00:00
Lakshay Goel 10 Reputation points

2023-02-18T13:50:16.6066667+00:00

i am trying to use the function
Viorel 122.6K Reputation points

2023-02-18T14:09:45.6966667+00:00

Did you already solve the original problem about '_ptr'?
Lakshay Goel 10 Reputation points

2023-02-19T06:09:19.8766667+00:00

no i havent ,i am getting muliple errors related to _iobuf but if i get solution for one all the other will get resolve @Viorel
RLWA32 49,636 Reputation points

2023-02-19T21:40:38.94+00:00

Since the old code depended on undocumented CRT implementation details that are no longer publicly exposed a line by line migration may not be possible. From what has been described so far you may need to take a higher level view of the old code and replace it with code that uses documented functions from the UCRT to achieve equivalent results.
Lakshay Goel 10 Reputation points

2023-02-20T09:21:17.21+00:00

could you please help me out @Viorel
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-02-20T09:23:06.9366667+00:00
FILE struct is non-portable. You need to rewrite relevant snippet.
_fileno may help.
_read example:

if (( bytesread = _read( fh, buffer, nbytes )) <= 0 ) perror( "Problem reading file" ); else printf( "Read %u bytes from file\n", bytesread );
Lakshay Goel 10 Reputation points

2023-02-20T17:02:27.3833333+00:00

@Minxin Yu can i get a more simple approch ?

what about fileno?

syntax ?? fileno(_flag)??
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-02-21T06:07:33.03+00:00

syntax:
FILE *fp
_fileno(fp)
_filelength (fp->_file) ->_filelength(_fileno(fp))

1 answer

Your answer

Viorel 122.6K Reputation points

2023-02-16T18:37:55.91+00:00

It seems that the code uses some undocumented unrecommended internal variables. Show some details. Maybe the code can be normalised.
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-02-17T02:40:15.14+00:00

Could you provide a minimal reproducible example?
Lakshay Goel 10 Reputation points

2023-02-18T13:45:56.16+00:00

@Minxin Yu

@Viorel

link-https://stackoverflow.com/questions/44018520/porting-issue-in-visual-studio-2015-flag-is-not-a-member-of-iobuf

#include "iostream" using namespace std; #define mybuffer(param) ((param)->_flag & (_IOMYBUF)) int main() { mybuffer(stderr); // I don't understand what is the purpose of this line. // So, facing issue in replacing this code statement. return 0; }
Lakshay Goel 10 Reputation points

2023-02-18T13:49:29.2066667+00:00
Lakshay Goel 10 Reputation points

2023-02-18T13:50:16.6066667+00:00

i am trying to use the function
Viorel 122.6K Reputation points

2023-02-18T14:09:45.6966667+00:00

Did you already solve the original problem about '_ptr'?
Lakshay Goel 10 Reputation points

2023-02-19T06:09:19.8766667+00:00

no i havent ,i am getting muliple errors related to _iobuf but if i get solution for one all the other will get resolve @Viorel
RLWA32 49,636 Reputation points

2023-02-19T21:40:38.94+00:00

Since the old code depended on undocumented CRT implementation details that are no longer publicly exposed a line by line migration may not be possible. From what has been described so far you may need to take a higher level view of the old code and replace it with code that uses documented functions from the UCRT to achieve equivalent results.
Lakshay Goel 10 Reputation points

2023-02-20T09:21:17.21+00:00

could you please help me out @Viorel
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-02-20T09:23:06.9366667+00:00

FILE struct is non-portable. You need to rewrite relevant snippet.
_fileno may help.
_read example:

if (( bytesread = _read( fh, buffer, nbytes )) <= 0 ) perror( "Problem reading file" ); else printf( "Read %u bytes from file\n", bytesread );
Lakshay Goel 10 Reputation points

2023-02-20T17:02:27.3833333+00:00

@Minxin Yu can i get a more simple approch ?

what about fileno?

syntax ?? fileno(_flag)??
Minxin Yu 13,506 Reputation points Microsoft External Staff

2023-02-21T06:07:33.03+00:00

syntax:
FILE *fp
_fileno(fp)
_filelength (fp->_file) ->_filelength(_fileno(fp))

Answer 1

Hi, Lakshay Goel

_fileno(iop) can be used in _read.// before ( iop->_file)

nread= _read(_fileno(iop), ptr, to_read);

For _flag:
You can declare a variable int iop_flag separately or create a custom structure: You may need to define the values of _IOEOF and IOERR.

	struct MyFILE
	{
		FILE* fp=NULL;
		int _flag;
        ...... other members ....... 
	};

Best regards,

Minxin Yu

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how to fix migratation error in vs2019

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