# V3554\. AUTOSAR\. The standard input/output functions should not be used\.

This diagnostic rule is based on the [AUTOSAR](https://www.autosar.org/) \(AUTomotive Open System ARchitecture\) manual for software development\.

The standard library functions from the '<stdio\.h\>' / '<cstdio\>' and '<wchar\.h\>' header files can be dangerous\. Their behavior depends on the implementation\. Besides, their use might lead to undefined behavior\.

Look at the code fragment:

```cpp
#include <stdio.h>

void InputFromFile(FILE *file); // Read from 'file'

void foo()
{
  FILE *stream;
  ....
  InputFromFile(stream);
  fflush(stream);
}
```

First, code reads data via the 'stream' file descriptor, which is then passed to the 'fflush' function\. This sequence of operations leads to [undefined behavior](https://en.cppreference.com/w/c/io/fflush)\.

The analyzer issues a warning if it detects the use of any functions defined in the '<stdio\.h\>' / '<cstdio\>' and '<wchar\.h\>' header files:

* fopen;
* fclose;
* freopen;
* fflush;
* setbuf;
* setvbuf;
* etc\.

For example, the analyzer issues a warning for the code below:

```cpp
#include <stdio.h>

void foo(const char *filename, FILE *oldFd)
{
  FILE *newFd = freopen(filename, "r", oldFd);
  ....
}
```