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NOTE
Analyzers may include static analysis tools, tools within a compiler suite, or tools in other contexts.

• Call

*asynchronous-safe* \[[GNU Pth|AA. C References#GNU Pth]\]
A function is "async-safe" if it can called safely and without side effects from within a signal handler context. That is, it must be able to be interrupted at any point and run linearly out of sequence without causing an inconsistent state. Very few functions are asynchronous-safe. Some asynchronous-safe operations are listed below. If a function does anything not on the list, it is probably not asynchronous-safe:

• call the signal() function to reinstall a signal handler.
• unconditionally Unconditionally modify a volatile sig_atomic_t variable (as modification to this type is atomic).
• call Call the _Exit() function to immediately terminate program execution.
• Invoke an asynchronous-safe function, as specified by the implementation.

Few functions are portably asynchronous-safe.

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*free-standing environment* \[[Banahan 03|AA. C References#Banahan 03]\]
An environment without the C standard libraries. Common for stand-alone programs, such as operating systems or firmware.

*hosted environment* \[[Banahan 03|AA. C References#Banahan 03]\]
An environment that supplies the C standard libraries.

*implementation* \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\]
Particular set of software, running in a particular translation environment under particular control options, that performs translation of programs for, and supports execution of functions in, a particular execution environment.

*implementation-defined behavior* \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\]
Unspecified behavior where each implementation documents how the choice is made.

*locale-specific behavior* \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\]
Behavior that depends on local conventions of nationality, culture, and language that each implementation documents.

*reentrant* \[[Dowd 06|AA. C References#Dowd 06]\]
A function is reentrant if multiple instances of the same function can run in the same address space concurrently without creating the potential for inconsistent states.

*undefined behavior* \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\]
Behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which the standard imposes no requirements.  An example of undefined behavior is the behavior on integer overflow.

*unspecified behavior* \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\]
Behavior where the standard provides two or more possibilities and imposes no further requirements on which is chosen in any instance.

*validation* \[[IEC 61508-4|AA. C References#IEC 61508-4]\]
Confirmation by examination and provision of objective evidence that the particular requirements for a specific intended use are fulfilled.

data races.

NOTE
Tracking can be performed intraprocedurally, with various assumptions made about what happens at function call boundaries, or interprocedurally, where values are tracked flowing into function calls (directly or indirectly) as arguments and flowing back out either as return values or indirectly through arguments.
Data flow analysis may or may not track values flowing into or out of the heap or take into account global variables. When this specification refers to values flowing, the key point is contrast with variables or expressions because a given variable or expression may hold different values along different paths and a given value may be held by multiple variables or expressions along a path.

NOTE
If the value does not conform, either the path is diverted to avoid using the value or a different, known-conforming value is substituted—for example, adding a null character to the end of a buffer before passing it as an argument to the strlen function.

NOTE
The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status flags and control modes. Floating-point operations implicitly set the status flags; modes affect result values of floating-point operations. Implementations that support such a floating-point state are required to regard changes to it as side effects. These are detailed in Annex F of the C Standard.

NOTE
Tainted sources include

• • parameters to the main() function
  • the returned values from localeconv(), fgetc(), getc, getchar(), fgetwc(), getwc(), and getwchar()
  • the strings produced by getenv(), fscanf(), vfscanf(), vscanf(), fgets(), fread(), fwscanf(), vfwscanf(), vwscanf(), wscanf(), and fgetws()

NOTE
For the purposes of this definition, a pointer to an object that is not an element of an array behaves the same as a pointer to the first element of an array of length one with the type of the object as its element type. (See C Standard, 6.5.8, paragraph 4.)
For the purposes of this definition, an object can be considered to be an array of a certain number of bytes; that number is the size of the object as produced by the sizeof operator. (See C Standard, 6.3.2.3, paragraph 7.)

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Image Added Image Added Image Added Wiki Markup*verification* \[[IEC 61508-4|AA. C References#IEC 61508-4]\] Confirmation by examination and provision of objective evidence that the requirements have been fulfilled.