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[CPP-340] Add a fourth query, ArgumentsToImplicit.ql, to deal strictly with implicitly declared
 functions. TooManyArguments.ql will now deal with explicitly declared/prototyped functions.
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‎cpp/ql/src/Likely Bugs/Underspecified Functions/ArgumentsToImplicit.c‎

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void calls() {
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undeclared(); // GOOD
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undeclared(1); // BAD
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undeclared(1, 2); // BAD
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}

‎cpp/ql/src/Likely Bugs/Underspecified Functions/ArgumentsToImplicit.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>An implicitly-declared function is called with arguments.</p>
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<p>This may indicate that an incorrect function is being called, or that the signature
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(parameter list) of the called function is not known to the author.</p>
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<p>In C, an implicitly declared function is assumed to accept no arguments. Providing
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these arguments incurs an unneeded computational overhead, both
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in terms of time and of additional stack space.</p>
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</overview>
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<recommendation>
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<p>Call the function without any arguments.</p>
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</recommendation>
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<example><sample src="ArgumentsToImplicit.c" />
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</example>
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<references>
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<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>
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</references>
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</qhelp>

‎cpp/ql/src/Likely Bugs/Underspecified Functions/ArgumentsToImplicit.ql‎

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/**
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* @name Call with arguments to an implicitly declared function
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* @description A function call passed arguments even though the
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* function in question is only implicitly declared (and
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* hence accepting no arguments). This may indicate
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* that the code does not follow the author's intent.
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* @kind problem
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* @problem.severity warning
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* @precision very-high
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* @id cpp/arguments-to-implicit
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* @tags correctness
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* maintainability
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*/
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import cpp
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// True if there is no explicit definition of the function
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predicate hasNoExplicitDecl(Function f) {
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not exists(FunctionDeclarationEntry fde | fde = f.getADeclarationEntry() |
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not fde.isImplicit()
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)
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}
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// True if this file (or header) was compiled as a C file
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predicate isCompiledAsC(Function f) {
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exists(File file | file.compiledAsC() |
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file = f.getFile() or file.getAnIncludedFile+() = f.getFile()
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)
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}
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predicate isWhitelisted(Function f) {
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f instanceof BuiltInFunction
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or
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// The following list can be expanded as the need arises
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exists(string name | name = f.getName() |
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name = "static_assert" or
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name = "_Static_assert" or
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name = "strptime"
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)
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}
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from FunctionCall fc, Function f
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where
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f = fc.getTarget() and
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hasNoExplicitDecl(f) and
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isCompiledAsC(f) and
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not isWhitelisted(f) and
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fc.getNumberOfArguments() > 0
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select fc, "This call to an implicitly declared function $@ has arguments.", f, f.toString()

‎cpp/ql/src/Likely Bugs/Underspecified Functions/TooManyArguments.ql‎

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import cpp
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// True if function was ()-declared, but not (void)-declared or K&R-defined
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// or implicitly declared (i.e., lacking a prototype)
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predicate hasZeroParamDecl(Function f) {
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exists(FunctionDeclarationEntry fde | fde = f.getADeclarationEntry() |
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not fde.hasVoidParamList() and fde.getNumberOfParameters() = 0 and not fde.isDefinition()
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not fde.isImplicit() and
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not fde.hasVoidParamList() and
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fde.getNumberOfParameters() = 0 and
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not fde.isDefinition()
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)
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}
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‎cpp/ql/test/query-tests/Likely Bugs/Underspecified Functions/ArgumentsToImplicit.expected‎

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| test.c:28:3:28:12 | call to undeclared | This call to an implicitly declared function $@ has arguments. | test.c:27:3:27:3 | undeclared | undeclared |

‎cpp/ql/test/query-tests/Likely Bugs/Underspecified Functions/ArgumentsToImplicit.qlref‎

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Likely Bugs/Underspecified Functions/ArgumentsToImplicit.ql

‎cpp/ql/test/query-tests/Likely Bugs/Underspecified Functions/TooManyArguments.expected‎

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| test.c:23:3:23:16 | call to declared_empty | This call has more arguments than required by $@. | test.c:1:6:1:19 | declared_empty | declared_empty |
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| test.c:28:3:28:12 | call to undeclared | This call has more arguments than required by $@. | test.c:27:3:27:3 | undeclared | undeclared |
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| test.c:30:3:30:19 | call to not_yet_declared1 | This call has more arguments than required by $@. | test.c:30:3:30:3 | not_yet_declared1 | not_yet_declared1 |
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| test.c:30:3:30:19 | call to not_yet_declared1 | This call has more arguments than required by $@. | test.c:65:6:65:22 | not_yet_declared1 | not_yet_declared1 |
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| test.c:40:3:40:29 | call to declared_empty_defined_with | This call has more arguments than required by $@. | test.c:67:6:67:32 | declared_empty_defined_with | declared_empty_defined_with |

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