Our website uses cookies to enhance your browsing experience.
Accept
to the top
close form

Fill out the form in 2 simple steps below:

Your contact information:

Step 1
Congratulations! This is your promo code!

Desired license type:

Step 2
Team license
Enterprise license
** By clicking this button you agree to our Privacy Policy statement
close form
Request our prices
New License
License Renewal
--Select currency--
USD
EUR
* By clicking this button you agree to our Privacy Policy statement

close form
Free PVS‑Studio license for Microsoft MVP specialists
* By clicking this button you agree to our Privacy Policy statement

close form
To get the licence for your open-source project, please fill out this form
* By clicking this button you agree to our Privacy Policy statement

close form
I am interested to try it on the platforms:
* By clicking this button you agree to our Privacy Policy statement

close form
check circle
Message submitted.

Your message has been sent. We will email you at


If you do not see the email in your inbox, please check if it is filtered to one of the following folders:

  • Promotion
  • Updates
  • Spam

Webinar: C++ semantics - 06.11

>
>
>
V739. EOF should not be compared with a…
menu mobile close menu
Analyzer diagnostics
General Analysis (C++)
General Analysis (C#)
General Analysis (Java)
Micro-Optimizations (C++)
Diagnosis of 64-bit errors (Viva64, C++)
Customer specific requests (C++)
MISRA errors
AUTOSAR errors
OWASP errors (C#)
Problems related to code analyzer
Additional information
toggle menu Contents

V739. EOF should not be compared with a value of the 'char' type. Consider using the 'int' type.

Jan 19 2016

The analyzer detected that the EOF constant is compared with a variable of type 'char' or 'unsigned char'. Such comparison implies that some of the characters won't be processed correctly.

Let's see how EOF is defined:

#define EOF (-1)

That is, EOF is actually but the value '-1' of type 'int'. Let's see what complications may occur. The first example:

unsigned char c;
while ((c = getchar()) != EOF)
  { .... }

The unsigned variable 'c' can never refer to the negative value '-1', so the expression ((c = getchar) != EOF) is always true and an infinite loop occurs. An error like that would be noticed and fixed right off in a real program, so there's no need to discuss the 'unsigned char' type further.

Here's a more interesting case:

signed char c;
while ((c = getchar()) != EOF)
  { .... }

The getchar() function returns values of type 'int', namely numbers within the range 0 - 255 or the value -1 (EOF). The read value is assigned to a variable of type 'char'. This operation causes the character with the code 0xFF (255) to turn into -1 and be interpreted just the same way as the end of a file (EOF).

Users who use Extended ASCII Codes sometimes face an issue when one of the characters of their alphabet is incorrectly processed by programs.

For example, the last letter of the Russian alphabet is encoded with that very value 0xFF in the Windows-1251 encoding and is interpreted as EOF by some programs.

The fixed version of the code should look like this:

int c;
while ((c = getchar()) != EOF)

This diagnostic is classified as:

You can look at examples of errors detected by the V739 diagnostic.