SEI CERT C Coding Standard

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Code Block
bgColor#FFcccc
langc
#define END_OF_FILE -1
/* ... */
if (getchar() EOFEND_OF_FILE) {
   /* ... */
}

In this example, the programmer has mistakenly omitted the comparison operator from the conditional statement, which should be getchar() != END_OF_FILE. (See void MSC02-C. Avoid errors of omission.) After macro expansion, the conditional expression is incorrectly evaluated as a binary operation: getchar()-1. This statement is syntactically correct, even though it is certainly not what the programmer intended. Note that this example also violates DCL00-C. Const-qualify immutable objects.

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Code Block
bgColor#ccccff
langc
enum { END_OF_FILE = -1 };
/* ... */
if (getchar() != END_OF_FILE) {
   /* ... */
}

Exceptions

PRE02-C-EX1: A macro that expands to a single identifier or function call is not affected by the precedence of any operators in the surrounding expression, so its replacement list need not be parenthesized.

Code Block
#define MY_PID getpid()

PRE02-C-EX2: A macro that expands to an array reference using the array-subscript operator [], or an expression designating a member of a structure or union object using either the member-access . or -> operators is not affected by the precedence of any operators in the surrounding expression, so its replacement list need not be parenthesized.

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Failing to parenthesize macro replacement lists can cause unexpected results.

Recommendation

Severity

Likelihood

Remediation Cost

Priority

Level

PRE02-C

Medium

Probable

Low

P12

L1

Automated Detection

ToolVersionCheckerDescription
Axivion Bauhaus Suite

Include Page
Axivion Bauhaus Suite_V
Axivion Bauhaus Suite_V

CertC-PRE02
CodeSonar
Include Page
CodeSonar_V
CodeSonar_V

LANG.PREPROC.MACROEND

LANG.PREPROC.MACROSTART

Macro Does Not End With ) or }

Macro Does Not Start With ( or {

ECLAIR

Include Page
ECLAIR_V
ECLAIR_V

CC2.PRE02

Fully implemented
Helix QAC

Include Page
Helix QAC_V
Helix QAC_V

C3409
Klocwork
Include Page
Klocwork_V
Klocwork_V
MISRA.DEFINE.BADEXP
LDRA tool suite
Include Page
LDRA_V
LDRA_V

77

S
78

S

Fully implemented

PRQA QA-C Include PagePRQA QA-C_vPRQA QA-C_v3409

Parasoft C/C++test
Include Page
Parasoft_V
Parasoft_V
CERT_C-PRE02-a

Enclose in parentheses whole definition of a function-like macro

PC-lint Plus

Include Page
PC-lint Plus_V
PC-lint Plus_V

773, 973

Fully supported

Fully implemented

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

SEI CERT C++ Coding StandardVOID PRE02-CPP. Macro replacement lists should be parenthesized
ISO/IEC TR 24772:2013Operator Precedence/Order of Evaluation [JCW]
Pre-processor Directives [NMP]

Bibliography

[Plum 1985]Rule 1-1
[Summit 2005]Question 10.1

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