C / C++ / MFC

what I am doing regarding Heap corruption

11-Jan-23 20:43

Well, they claim the device independent one are faster (Bitmap Classifications - Win32 apps | Microsoft Learn[^].
You could arrange a test in order to have experimental evidence.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

ForNow10-Jan-23 15:33

10-Jan-23 15:33

Since many have been so kind as to help me out i will spell out exactly what I am doing

The Windows Program is a client to Z/os Mainframe program. I download a file (variable blocked) the output of a MainFrame Assembler program listing. This on the mainframe is called a sysadata file.

The Windows exe calls the dll to basically convert the binary representation of the listing into readable format

The routine I having the exception in is a subroutine called by another routine in the DLL The file i/o is done in the DLL.

I think I am going to take out all the storage allocation out of the DLL is just causing me all sorts of problems the structure I'll pass from the exe to the dll will

have the maximum amount of storage I need I do a number of STL objects such as maps in the DLL basically a number of map objects I have already generated them I hoping that when

the exe needs the information from the DLL I dont have issues referencing them

CPallini10-Jan-23 20:08

10-Jan-23 20:08

Quote:
The Windows exe calls the dll to basically convert the binary representation of the listing into readable format

A simple workaround would be moving that code inside the executable.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

ForNow11-Jan-23 1:33

11-Jan-23 1:33

A little bit of a background I am basically a mainframe assembler language programmer I have worked for software vendor and IBM on their OS after 2000 I started getting layed off all over the place. it was it was suggested to me that I learn something new I started with C then Windows then MFC, along the way I got a Job with the US federal govt the IRS it is my day job Im on the east cost in NY. When It came to renew my IBM MainFrame yearly license and I inquired why the cost was higher than others they told me I have a right to sell the software I develop. I then started to focus my attention on that The z/os as a server and a Windows client

Back to why I didnt make this code part of the .exe. The .DLL would be invoked by multiple user. Every user of the .exe would need to perform this functionality

Again thank you for help I could never have gotten this far without the kindness of people like yourself

CPallini11-Jan-23 1:40

11-Jan-23 1:40

You are welcome.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Mircea Neacsu11-Jan-23 7:04

Mircea Neacsu

11-Jan-23 7:04

I don't know the details of your application, but in the PC/Windows world it's rare to have more than one user running on the same machine. Even if you have more than one user, each process (.exe program) has it's own separate memory space. Using a DLL instead of a single program to save memory makes little sense these days. I know some people might disagree with me, but this is a broad brush picture. Anyway it doesn't pay off in terms of complications it adds to your project, doubly so if you are a newcomer to this field.

In short, my recommendation would be to give up on having a DLL and putting everything in a single program. If latter on, when the program is working well, you discover that using a DLL makes sense, you can change it. In the meantime you would have gained more familiarity with the OS/tools/programming language and it would be easier for you to transition.

Just my $0.02

Mircea

ForNow11-Jan-23 7:25

11-Jan-23 7:25

I removed all of the storage allocations out of my DLL and it seemed to worked by tonite I should be able put this piece to rest.

if not i will consider and/or take your advice

thanks

Heap Storage Corruption

ForNow10-Jan-23 3:44

10-Jan-23 3:44

Hi
I have the following code which I basically take a hex array and convert it to a ascii char * e.g 0X47F0F01A so the array becomes 303770307030316500
I marked off where I get dialogbox message from CRT and I cannt for the life of me figure out why
the memcpy where I mark off the string with a null is 8 bytes into the 70 bytes allocated

C++

// converts character array
// to string and returns it
char* convertToString(unsigned char* a, int size)
{
    int i;
    char ch;
    char getch(char);
    char* t = new char[70];
    char* k = t;
    char thenullptr = 0x00;
    char* s;
    if (size == 80)
        __debugbreak();
    for (i = 0; (i < size && i < 62); i++) {
        ch = a[i];
        ch = ch >> 4;
        ch = ch & 0x0f;
        ch = getch(ch);
        memcpy(k, &ch, 1);
        k++;
        ch = a[i];
        ch = ch & 0x0f;
        ch = getch(ch);
        memcpy(k, &ch, 1);
        k++;

    }
    if (i >= 62)
    {
        s = new char[63];
        ::memcpy(s, t, 62);
        k = s + 62;
        ::memcpy(k, &thenullptr, 1);    <------- call which causes read exception or overwrite

        delete t;
        return s;
    }


    ::memcpy(k, &thenullptr, 1);
    s = new char(strlen(t) + 1);
;
    ::memcpy(s, t, strlen(t) + 1);
    delete t;
    return s;
}

char getch(char ch)
{

    if (ch <= 0x09)
        ch += 48;
    else
        ch += 55;
    return ch;
}

Victor Nijegorodov10-Jan-23 5:08

Victor Nijegorodov

10-Jan-23 5:08

ForNow wrote:

C++

s = new char[63];
::memcpy(s, t, 62);
k = s + 62;
::memcpy(k, &thenullptr, 1);    <------- call which causes read exception or overwrite

why are you doing it so complicated?
Why not just

C++

s = new char[63] {0};
::memcpy(s, t, 62);

and you won't need to copy the terminated 0x00 byte.
Or just set it form the very begin:

C++

s = new char[63];
s[62] = '\0';
::memcpy(s, t, 62);

modified 10-Jan-23 11:17am.

ForNow10-Jan-23 5:25

10-Jan-23 5:25

Ok let me redo it thanks for responding thing is it doesn’t happen the first time the sub gets called only after a number if calls
Thank you again

k505410-Jan-23 6:17

k5054

10-Jan-23 6:17

That would suggest you probably have a bug elsewhere in you program. Maybe a buffer overflow or an uninitialized variable is writing where it shouldn't. If you haven't already, turn up the warning level on the compiler, and then fix everything it flags. If this still happens, you'll need to dig into your debugger and look into watch points and the like.

Keep Calm and Carry On

Graham Breach10-Jan-23 6:22

Graham Breach

10-Jan-23 6:22

You are using new[], so you must use a matching delete[]:

C++

char* t = new char[70];

// do stuff with t

delete[] t;

This might not be the cause of the problem you are having, but it will cause problems.

ForNow10-Jan-23 6:44

10-Jan-23 6:44

Just saw that but that is only for C++ as I build this DLL as C

Before thank you

Graham Breach10-Jan-23 6:51

Graham Breach

10-Jan-23 6:51

C doesn't have new/delete at all - you are writing C++

CPallini10-Jan-23 7:21

10-Jan-23 7:21

As far as I know it is not a good idea to allocate memory using a runtime (the DLL's one) and releasing it using another one (the application linking with the DLL). See, for instance:
Potential Errors Passing CRT Objects Across DLL Boundaries | Microsoft Learn[^].

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

ForNow10-Jan-23 7:26

10-Jan-23 7:26

that's is my scenario I pass a hex array pointer to DLL function and allocate the storage there and pass the pointer back to the application I have to read what you sent I have Dr appointment in 15 min but thanks for the info

CPallini10-Jan-23 7:40

10-Jan-23 7:40

You are welcome.
BTW, Good luck with the doctor.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

CPallini10-Jan-23 8:32

Re: Why isn't my semi-editable ComboBox drawing the text in gray when the dropdown list isn't showing?

10-Jan-23 8:32

If I got you, the code should return the hexadecimal representation of a bunch of bytes.
In order to avoid CRT-conflicts, you have to make the caller responsible of the output buffer allocation/deallocation. Something like this

C++

#include <iostream>
#include <cstddef>
using namespace std;

// in [INPUT]  - the binary array we wish to represent with an hex string
// size_in [INPUT] - the size (bytes) of the binary array
// out [OUTPUT] - the buffer receiving the hexadecimal representation of the binary data
// out_size [INPUT] - the size of the buffer. It should be at least (size_in*2+1) in order ot represent all the input data
size_t to_hex( unsigned char in[], size_t size_in, char out[], size_t size_out)
{
  size_t n;
  for (n=0; (n < size_in) && (n < (size_out-1)b/2); ++n)
  {
    unsigned char nibble;
    nibble = (in[n] >> 4); // the MSB nibble
    out[2*n] = nibble < 10 ? nibble + '0' : nibble - 10 + 'A';
    nibble = (in[n] & 15); // the LSB nibble
    out[2*n+1] = nibble < 10 ? nibble + '0' : nibble - 10 + 'A';
  }

  if ( 2*n < size_out)
    out[2*n] = '\0';

  return n;
}

// a little test
int main()
{
  unsigned char small[] = { 0x25, 0x37, 0x48, 0x42, 0x42 };

  char buffer[41];

  size_t size = to_hex( small, sizeof(small), buffer, sizeof(buffer));
  cout << "converted bytes " << size << ", hex string " << buffer << "\n";


  unsigned char large[256];
  for (size_t n=0; n<256; ++n)
  {
    large[n] = n;
  }

  size = to_hex( large, sizeof(large), buffer, sizeof(buffer));
  cout << "converted bytes " << size << ", hex string " << buffer << "\n";
}

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

To be deleted...

arnold_w10-Jan-23 1:01

arnold_w

10-Jan-23 1:01

Ooops, wrong forum section. Can a moderator please delete this thread (the Delete link is disabled for me)?

modified 10-Jan-23 8:24am.

Richard Deeming10-Jan-23 2:03

Richard Deeming

10-Jan-23 2:03

That doesn't look like C++ to me. Are you sure you didn't mean to post this in the C# forum[^] instead?

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Re: Why isn't my semi-editable ComboBox drawing the text in gray when the dropdown list isn't showing?

David Crow10-Jan-23 2:07

David Crow

10-Jan-23 2:07

If this is truly C# code, mightn't you be better served posting it in the C# forum?

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

Trying to Disable string operator=

ForNow8-Jan-23 16:55

Re: Trying to Disable string operator=

8-Jan-23 16:55

Hi
I have a number of hex data I am trying to get to printable data I mean ascii

I read them as a byte[] array where byte is typedef for usigned char

I just got this idea it might be easier to manipulate it as string i mean like std::string

so I developed this routine

C++

// converts character array
// to string and returns it
string convertToString(unsigned char* a, int size)
{
    int i;
    string s = "";
    for (i = 0; i < size; i++) {
        s += a[i];
    }
    return s;
}

Here is the piece of code that calls it

C++

returnsource->stmt = convertToString(sourcerecordpointer->statementnumber, 4)

here is the definition

C++

BYTE statementnumber[4];

the data in statement ithe statement number in hex so statement 1 would be

x'00000001'
so my goal the would be to retrun

retrun->stmt as character 0001 or x30303031

Now me thinks that since return->stmt is defined as a string

C++

struct source
{
	string stmt;
	string loc;
	string addr1;
	string  addr2;

that the string operator= is invoked becasue of this

I end up here in Microsoft code in a member utility and get a read exception

this is the path

C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.34.31933\include\utility

is there any way I can tell MSVC compiler that all I am trying to do with = operator is accept a return value from my subroutine

C++

template <class _Ty, class _Other = _Ty>
_CONSTEXPR20 _Ty exchange(_Ty& _Val, _Other&& _New_val) noexcept(
    conjunction_v<is_nothrow_move_constructible<_Ty>, is_nothrow_assignable<_Ty&, _Other>>) {
    // assign _New_val to _Val, return previous _Val
    _Ty _Old_val = static_cast<_Ty&&>(_Val);
    _Val         = static_cast<_Other&&>(_New_val);
    return _Old_val;
}

k50548-Jan-23 17:49

k5054

8-Jan-23 17:49

Since one of the constructors for std::string is

C++

std::string(const char *, size_t count)

you can do your assignment using

C++

unsigned char datum[6]{ 'A', 'B', 'C', 'D', 'E', 'F' };  // a non-nul terminated sequence of bytes
std::string str(reinterpret_cast<const char *>(datum), 4); // assuming we just want the first 4 bytes from datum

Since you're getting a read exception, that suggests to me that given

C++

returnsource->stmt = convertToString(sourcerecordpointer->statementnumber, 4);

then probably your sourcrecordpointer is invalid.

Keep Calm and Carry On

Re: Trying to Disable string operator=

ForNow8-Jan-23 18:02