# Consistent Use

+ semmlecode-cpp-queries/Likely Bugs/Likely Typos/FutileParams.ql: /Correctness/Common Errors

void no_argument();

void one_argument(int x);

void calls() {

no_argument(1) // BAD: `no_argument` will accept and ignore the argument

one_argument(1); // GOOD: `one_argument` will accept and use the argument

no_argument(); // GOOD: `no_argument` has not been passed an argument

}

<!DOCTYPE qhelp PUBLIC

"-//Semmle//qhelp//EN"

"qhelp.dtd">

<qhelp>

<overview>

<p>A function is called with arguments despite having an empty parameter list. This may indicate

that the incorrect function is being called, or that the author misunderstood the function.</p>

<p>In C, a function declared with an empty parameter list `()` is considered to have an unknown

parameter list, and therefore can be called with any set of arguments. To declare a function

which takes no arguments, you must use `(void)` as the parameter list in any forward declarations.

In C++, either style of declaration indicates that the function accepts no arguments.</p>

</overview>

<recommendation>

<p>Call the function without arguments, or call a different function that expects the arguments

being passed.</p>

</recommendation>

<example><sample src="FutileParams.c" />

</example>

<references>

<li>SEI CERT C++ Coding Standard: <a href="https://wiki.sei.cmu.edu/confluence/display/c/DCL20-C.+Explicitly+specify+void+when+a+function+accepts+no+arguments"> DCL20-C. Explicitly specify void when a function accepts no arguments </a></li>

</references>

</qhelp>

import cpp

from Function f, FunctionCall fc

where fc.getTarget() = f

and f.getNumberOfParameters() = 0

and not f.isVarargs()

and fc.getNumberOfArguments() != 0

and not f instanceof BuiltInFunction

and exists(FunctionDeclarationEntry fde | fde = f.getADeclarationEntry() | not fde.isImplicit())

select fc, "This call has arguments, but $@ is not declared with any parameters.", f, f.toString()

| test.c:8:3:8:16 | call to declared_empty | This call has arguments, but $@ is not declared with any parameters. | test.c:1:6:1:19 | declared_empty | declared_empty |

| test.c:14:3:14:19 | call to not_yet_declared1 | This call has arguments, but $@ is not declared with any parameters. | test.c:14:3:14:3 | not_yet_declared1 | not_yet_declared1 |

| test.c:14:3:14:19 | call to not_yet_declared1 | This call has arguments, but $@ is not declared with any parameters. | test.c:25:6:25:22 | not_yet_declared1 | not_yet_declared1 |

Likely Bugs/Likely Typos/FutileParams.ql

void declared_empty();

void declared_void(void);

void declared_with(int);

void declared_empty_defined_with();

void test() {

declared_empty(); // GOOD

declared_empty(1); // BAD

declared_void(); // GOOD

declared_with(1); // GOOD

undeclared(1); // GOOD

not_yet_declared1(1); // BAD

not_yet_declared2(1); // GOOD

declared_empty_defined_with(); // BAD [NOT DETECTED]

declared_empty_defined_with(1); // GOOD

int x;

declared_empty_defined_with(&x); // BAD [NOT DETECTED]

declared_empty_defined_with(x, x); // BAD [NOT DETECTED]

}

void not_yet_declared1();

void not_yet_declared2(int);

void declared_empty_defined_with(int x) {

// do nothing

}

void cpp_varargs(...);

void bar();

void test() {

cpp_varargs(); // GOOD

cpp_varargs(1); // GOOD

__builtin_constant_p("something"); // GOOD: builtin

}