What's the Difference Between Indeterminate and Undefined Behavior in C ?

Understanding Indeterminate Behavior in C : Distinguishing from Undefined Behavior

C distinguishes between various levels of ambiguous behavior, including indeterminate and undefined behavior.

Indeterminate Behavior

• Occurs when the standard provides no defined behavior for a particular scenario.
• The implementation has discretion to choose a specific behavior, possibly varying from case to case.
• The standard does not mandate consistency or documentation of the chosen behavior.

Undefined Behavior

• Represents the most extreme level of ambiguity where all bets are off.
• The program's behavior becomes unpredictable and can lead to crashes, memory corruption, or anomalous results.

Implementation-Defined Behavior

• Similar to indeterminate behavior, but the implementation must choose a specific behavior and document it.
• Ensures consistency within the implementation.
• May vary between different implementations.

Unspecified Value

• A valid value but the standard does not specify its value.
• May change in subsequent program executions.

Implementation-Defined Value

• A valid value that the implementation must define and use consistently.
• May differ between implementations.

Indeterminate Value

• Even more ambiguous than unspecified value.
• Can either be an unspecified value or a trap representation.
• Trap representation triggers undefined behavior if assigned to other variables.

Applicability to C Code

The concepts of indeterminate and undefined behavior are generally applicable to both C and C codes. The C standard uses similar definitions with inherent vagueness. It is crucial to understand these distinctions to effectively utilize these languages and handle uncertainties in a robust manner.

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