MISRA.RESOURCES.FILE.READ_ONLY_WRITE.2012

There shall be no attempt to write to a stream which has been opened as read-only.

MISRA C 2012 Rule 22.4: There shall be no attempt to write to a stream which has been opened as read-only

Category: Mandatory

Analysis: Undecidable, System

Applies to: C90, C99

Rationale

The Standard does not specify the behaviour if an attempt is made to write to a read-only stream. For this reason it is considered unsafe to write to a read-only stream.

Example

#include <stdio.h>

void fn ( void ) 
{  
  FILE *fp = fopen ( "tmp", "r" );

  ( void ) fprintf ( fp, "What happens now?" ); /* Non-compliant */

  ( void ) fclose ( fp ); 
}

See also

Rule 21.6