LANG.TYPE.MDS : Misplaced Digit Separator

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CodeSonar^® 9.2p0

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C and C++

LANG.TYPE.MDS : Misplaced Digit Separator

Summary

A numeric literal contains one or more digit separators ('), but the separator usage does not conform to the following policy.

decimal, octal	separator every 3 digits
hexadecimal	separator every 2 digits
binary	separator every 4 digits

A numeric literal with no digit separators will not trigger a warning of this class.

Digit separators were introduced in C++14 and C23. If you are using an earlier version, digit separators may cause a compiler error.

Properties

Class Name

Misplaced Digit Separator

Significance

style

Mnemonic

LANG.TYPE.MDS

Categories

AUTOSARC++14	AUTOSARC++14:A13-6-1	Digit sequences separators ' shall only be used as follows: (1) for decimal, every 3 digits, (2) for hexadecimal, every 2 digits, (3) for binary, every 4 digits.
CWE	CWE:1076	Insufficient Adherence to Expected Conventions

Availability

Available for C and C++.

Enabling

Checks for this warning class are disabled by default, and require the unnormalized C ASTs for the project. To enable them, add the following WARNING_FILTER rule and RETAIN_UNNORMALIZED_C_AST specification to the project configuration file.

RETAIN_UNNORMALIZED_C_AST = Yes
WARNING_FILTER += allow class="Misplaced Digit Separator"

Note that retaining the unnormalized ASTs will increase the disk space used to store the project representation, and may make the analysis take longer.

Example

// Decimals and octals: every three digits (or none)
int jenny = 867'5309;          // 'Misplaced Digit Separator' warning issued here
int taxi = 1'729;                                    // ok
int alldigits = 1234567'890;   // 'Misplaced Digit Separator' warning issued here
float pi_approx = 3.141'15;                          // ok
double e_approx = 2.7182818;                         // ok
int all = 0777;                                      // ok

// Hexadecimals:  every two digits (or none)
int mask = 0xff'ff;                                  // ok
int mask_nosep = 0xffff;                             // ok
int mask_badsep = 0xf'fff;     // 'Misplaced Digit Separator' warning issued here

// Binary numbers: every four digits (or none)
int sig = 0b1101'1111;                               // ok
int sig_nosep = 0b11011111;                          // ok
int sig_badsep = 0b11'011'111; // 'Misplaced Digit Separator' warning issued here

Relevant Configuration File Parameters

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

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