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The C Standard, 7.2123.9.3 paragraph 2 [ISO/IEC 9899:20112024], defines the following behavior for fsetpos():

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Invoking the fsetpos() function with any other values for pos is undefined behavior 181.

Noncompliant Code Example

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Only the return value of an fgetpos() call is a valid argument to fsetpos(); passing a value of type fpos_t that was created in any other way is undefined behavior 181.

Compliant Solution

In this compliant solution, the initial file position indicator is stored by first calling fgetpos(), which is used to restore the state to the beginning of the file in the later call to fsetpos():

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Misuse of the fsetpos() function can position a file position indicator to an unintended location in the file.

Rule	Severity	Likelihood	Detectable	RepairableRemediation Cost	Priority	Level
FIO44-C	Medium	Unlikely	No	MediumNo	P4P2	L3

Automated Detection

Tool

Version

Checker

Description

CodeSonar

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	CodeSonar_V
	CodeSonar_V

(customization)

Users can add a custom check for violations of this constraint.

Compass/ROSE

Can detect common violations of this rule. However, it cannot handle cases in which the value returned by fgetpos() is copied between several variables before being passed to fsetpos()

Cppcheck Premium

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