IO.IOWOP : Input After Output Without Positioning

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CodeSonar^® 9.2p0

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IO.IOWOP : Input After Output Without Positioning

Summary

Input is read from a stream, and output is subsequently written to the same stream without an intervening positioning operation.

Properties

AUTOSARC++14

AUTOSARC++14:A27-0-3

Alternate input and output operations on a file stream shall not be used without an intervening flush or positioning call.

MisraC++2023

MisraC++2023:0.3.2

A function call shall not violate the function's preconditions

MisraC++2023:30.0.2

Reads and writes on the same file stream shall be separated by a positioning operation

CERT-C

CERT-C:FIO39-C

Do not alternately input and output from a stream without an intervening flush or positioning call

CERT-CPP

CERT-CPP:FIO50-CPP

Do not alternately input and output from a file stream without an intervening positioning call

Example

#include <stdio.h>

void out_in(FILE * f){
    (void)fputc('b', f);
    (void)fgetc(f);     /* 'Input after Output without Positioning' warning issued here */
}

int out_other_in(FILE * f){
    int x = 1;
    int y = 2;
    (void)fputc('b', f);
    x += y;
    (void)fgetc(f);      /* 'Input after Output without Positioning' warning issued here
                          * - input operation does not need to immediately follow output operation
                          */
    return x;
}

void callee_with_in(FILE *f);
void out_then_call(FILE *f){
  (void)fputc('b', f);
  callee_with_in(f);
}

void callee_with_in(FILE *f){
  (void)fgetc(f);        /* 'Input after Output without Positioning' warning issued here
                          * - no intervening positioning operation when callee_with_in() is called from out_then_call()
                          */
}

void out_position_in(FILE * f){
    (void)fputc('b', f);
    (void)fseek(f, 0, SEEK_SET);
    (void)fgetc(f);                  /* ok: intervening call to fseek() */
}

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.