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/**

* Provides default predicates that specify information about

* the behavior of the program being analyzed.

* This can be overridden for particular code bases in `Options.qll`.

import cpp

import semmle.code.cpp.controlflow.Dataflow

import semmle.code.cpp.commons.Synchronization

private import semmle.code.cpp.controlflow.internal.ConstantExprs

private import Options as CustomOptions

/**

* Default predicates that specify information about the behavior of

* the program being analyzed.

class Options extends string {

Options() { this = "Options" }

/**

* Holds if we wish to override the "may return NULL" inference for this

* call. If this holds, then rather than trying to infer whether this

* call might return NULL, we will instead test whether `returnsNull`

* holds for it.

* By default, this handles the `Xstrdup` function used by the CVS

* project.

predicate overrideReturnsNull(Call call) {

// Used in CVS:

call.(FunctionCall).getTarget().hasGlobalName("Xstrdup")

}

/**

* Holds if this call may return NULL. This is only used if

* `overrideReturnsNull` holds for the call.

* By default, this handles the `Xstrdup` function used by the CVS

* project.

predicate returnsNull(Call call) {

// Used in CVS:

call.(FunctionCall).getTarget().hasGlobalName("Xstrdup") and

nullValue(call.getArgument(0))

}

/**

* Holds if a call to this function will never return.

* By default, this holds for `exit`, `_exit`, `_Exit`, `abort`,

* `__assert_fail`, `longjmp`, `__builtin_unreachable` and any

* function with a `noreturn`, `__noreturn__`, or `_Noreturn`

* attribute or `noreturn` specifier.

predicate exits(Function f) {

f.getAnAttribute().hasName(["noreturn", "__noreturn__", "_Noreturn"])

f.getASpecifier().hasName("noreturn")

f.hasGlobalOrStdName([

"exit", "_exit", "_Exit", "abort", "__assert_fail", "longjmp", "__builtin_unreachable"

])

}

/**

* Holds if evaluating expression `e` will never return, or can be assumed

* to never return. For example:

* ```

* __assume(0);

* ```

* (note that in this case if the hint is wrong and the expression is reached at

* runtime, the program's behavior is undefined)

predicate exprExits(Expr e) {

e.(AssumeExpr).getChild(0).(CompileTimeConstantInt).getIntValue() = 0

}

/**

* Holds if function `f` should always have its return value checked.

* By default holds only for `fgets`.

predicate alwaysCheckReturnValue(Function f) { f.hasGlobalOrStdName("fgets") }

/**

* Holds if it is reasonable to ignore the return value of function

* call `fc`.

* By default holds for calls to `select` where the first argument is

* `0` (commonly used as a way of sleeping), and any call inside a

* macro expansion.

predicate okToIgnoreReturnValue(FunctionCall fc) {

fc.isInMacroExpansion()

// common way of sleeping using select:

fc.getTarget().hasGlobalName("select") and

fc.getArgument(0).getValue() = "0"

}

Options getOptions() { any() }

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