How Does C Differ Subtly from C in Terms of Compilation and Syntax?
Dec 17, 2024 am 04:54 AMC's Subtle Departures from C
While it's widely believed that C is a subset of C , a closer examination reveals subtle differences. Here are some instances where code that compiles in C encounters obstacles in C :
No Tentative Definitions
In C , redefining variables is illegal, unlike in C, where tentative definitions allow for subsequent redefinitions.
Array Type Incompatibility
C distinguishes between array types with sizes and without, making int[] and int[N] incompatible. C, however, allows them to be used interchangeably.
K&R Function Syntax
C disallows the K&R style of function definition where the function parameter list directly follows the return type.
Nested Struct Scope
C defines nested structs to have class scope, while C adheres to the earlier behavior of local scope.
Default int
In C , using "auto" without an explicit type specifier is invalid, unlike in C, where it defaults to int.
Additional C99 Incompatibilities
C99 introduced further discrepancies:
Array Dimension Specifiers
C disallows declaration specifiers in array dimensions of function parameters, which is permitted in C.
Variable Length Arrays
C omits support for variable length arrays, whereas C allows them by declaring arrays with non-constant sizes.
Flexible Array Members
C lacks flexible array members within structs, a feature present in C.
Restrict Qualifier
C introduces the restrict qualifier to assist in aliasing analysis, but it's not supported in C.
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