import cpp

import codingstandards.c.misra

import codingstandards.cpp.TypeUses

from UserType s

not isExcluded(s, DeadCodePackage::unusedTagDeclarationQuery()) and

// ignore structs without a tag name

not s.getName() = "struct <unnamed>" and

// typedefs do not have a "tag" name, so this rule does not apply to them

not s instanceof TypedefType and

// Not mentioned anywhere

not exists(TypeMention tm | tm.getMentionedType() = s) and

// Exclude any struct that is fully generated from a macro expansion, as it may be used in other

// expansions of the same macro.

// Note: due to a bug in the CodeQL CLI version 2.9.4, this will currently have no effect, because

// `isInMacroExpansion` is broken for `UserType`s.

not s.isInMacroExpansion()

select s, "struct " + s.getName() + " has an unused tag."

| test.c:4:8:4:9 | S2 | struct S2 has an unused tag. |

| test.c:7:16:7:17 | S3 | struct S3 has an unused tag. |

| test.c:17:6:17:7 | E1 | struct E1 has an unused tag. |

| test.c:31:10:31:11 | S7 | struct S7 has an unused tag. |

| test.c:50:8:50:10 | S10 | struct S10 has an unused tag. |

| test.c:66:3:66:14 | S13 | struct S13 has an unused tag. |

| test.c:79:8:79:10 | s14 | struct s14 has an unused tag. |

rules/RULE-2-4/UnusedTagDeclaration.ql

struct S1 { // COMPLIANT

int x;

};

struct S2 { // NON_COMPLIANT

int x;

};

typedef struct S3 { // NON_COMPLIANT

int x;

} T1;

typedef struct S4 { // COMPLIANT

int x;

} T2;

struct S5 { // COMPLIANT

int x;

};

typedef struct S5 T3;

enum E1 { state1, state2 }; // NON_COMPLIANT

enum E2 { state3, state4 }; // COMPLIANT

struct { // COMPLIANT - no tag

int x;

} s6;

void test() {

struct S1 s1;

T1 t1;

t1.x = 0; // Field access on struct S3

T2 t2;

struct S4 s4;

int x = state1; // enum access on E1

enum E2 e2;

struct S7 { // NON_COMPLIANT

int x

} s7;

struct S8 { // COMPLIANT

int x

} s8;

struct S8 s8_2;

struct S11 { // COMPLIANT

int x;

} foo(struct S11 s);

}

struct S9 { // COMPLIANT

int x;

} test_2() {

return (struct S9){0};

}

struct S10 { // NON_COMPLIANT

int x;

} * test_3() {

return 0;

}

struct S12 { // COMPLIANT

int x;

} foo(struct S12 s);

#define STRUCT_MACRO \

struct S13 { \

int x; \

};

void testMacroNameUsed() {

STRUCT_MACRO // COMPLIANT[FALSE_POSITIVE] - although the struct generated by

// the macro is never used in this expansion, it may be used in

// other expansions, so we don't want to report it as unused

}

void testMacroNameNotUsed() {

STRUCT_MACRO // COMPLIANT - S13 is used in this expansion

struct S13 s13_2;

}

#define PARTIAL \

{ int x; }

struct s14 PARTIAL; // NON_COMPLIANT - affected by macro, but not fully

// generated, so fair to report as unused

import cpp

select any(Location l).toString() as s, count(Location l | l.toString() = s)