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According to subclause 6.2.7 of the C Standard [AA. Bibliography#ISO-ISO/IEC 9899-:2011],

All declarations that refer to the same object or function shall have compatible type; otherwise, the behavior is undefined.

(See also CC. Undefined Behavior#ub_15 undefined behavior 14 of Annex J.)

Further, according to subclause 6.4.2.1,

Any identifiers that differ in a significant character are different identifiers. If two identifiers differ only in nonsignificant characters, the behavior is undefined.

(See also CC. Undefined Behavior#ub_31 undefined behavior 30 of Annex J.)

Identifiers in mutually visible scopes must be deemed unique by the compiler to prevent confusion about which variable or function is being referenced. BB. Definitions#implementation Implementations can allow additional nonunique characters to be appended to the end of identifiers, making the identifiers appear unique while actually being indistinguishable.

...

Code Block

bgColor	#FFcccc
lang	c

extern int *global_symbol_definition_lookup_table_a;
extern int *global_symbol_definition_lookup_table_b;

Compliant Solution (Source Character Set)

...

Code Block

bgColor	#ccccff
lang	c

extern int *a_global_symbol_definition_lookup_table;
extern int *b_global_symbol_definition_lookup_table;

Noncompliant Code Example (Universal Character Names)

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Code Block

bgColor	#FFcccc
lang	c

extern int *\U00010401\U00010401\U00010401\U00010401;
extern int *\U00010401\U00010401\U00010401\U00010402;

Compliant Solution (Universal Character Names)

...

Code Block

bgColor	#ccccff
lang	c

extern int *\U00010401\U00010401\U00010401\U00010401;
extern int *\U00010402\U00010401\U00010401\U00010401;

Risk Assessment

Nonunique identifiers can lead to abnormal program termination, denial-of-service attacks, or unintended information disclosure.

Rule	Severity	Likelihood	Detectable

Remediation Cost

Repairable	Priority	Level
DCL23-C	Medium	Unlikely

Low

Yes

P6

L2

Automated Detection

Tool

Version

Checker

Description

Astrée

Include Page

	Astrée_V
	Astrée_V

Supported indirectly via MISRA C:2012 Rules 5.1, 5.2, 5.3, 5.4 and 5.5.

Axivion Bauhaus Suite

Include Page

	Axivion Bauhaus Suite_V
	Axivion Bauhaus Suite_V

CertC-DCL23

CodeSonar

Include Page

	CodeSonar_V
	CodeSonar_V

LANG.ID.ND.

STRUCT.DECLTYPE

EXT
LANG.ID.ND.MM
LANG.ID.ND.MO
LANG.ID.ND.NEST
LANG.ID.ND.SS

LANG.ID.NU.EXT
LANG.ID.NU.INT
LANG.ID.NU.LIBFN
LANG.ID.NU.TAG
LANG.ID.NU.TYPE

LANG.STRUCT.DECL.MGT

Non-distinct identifiers: external names
Non-distinct identifiers: macro/macro
Non-distinct identifiers: macro/other
Non-distinct identifiers: nested scope
Non-distinct identifiers: same scope

Non-unique identifiers: external name
Non-unique identifiers: internal name
Library Function Override
Non-unique identifiers: tag
Non-unique identifiers: typedef

Global variable declared with different types

Compass/ROSE

Can detect some violations of this rule but cannot flag violations involving universal names

CERT C Rules implemented in the

Helix QAC

Include Page