C Language Extensions
- Updated2023-02-21
- 5 minute(s) read
C Language Extensions
The LabWindows/CVI compiler has several extensions to the C language. The purpose is to make the LabWindows/CVI compiler compatible with external compilers that use common C extensions.
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Note For information about the C language extensions supported in different versions of LabWindows/CVI, visit ni.com/info and enter the following Info Code: CLangExt. |
The following table lists the supported Clang and GCC extentions:
| Supported | ||
|---|---|---|
| C Extensions | GNU89 | C99 |
| Alignment | Yes | Yes |
| Alternate Keywords: __const__, __asm__, etc., for header files. | Yes | Yes |
| Asm Labels: Give a name to variables and functions for __asm__ use (use __asm__ keyword only). | Yes | Yes |
| Atomic Builtins: Built-in functions for atomic memory access. | Partial: all except __sync_fetch_and_nand and __sync_nand_and_fetch. | Partial: all except __sync_fetch_and_nand and __sync_nand_and_fetch. |
| Attribute Syntax: Formal syntax for attributes. | Yes | Yes |
| Attributes on Enumerators | Yes | Yes |
| Availability Attribute | No | No |
| Binary constants: Binary constants using the 0b prefix. | Yes, with warning | Yes, with warning |
| Blocks | No | No |
| _Bool data type | Yes | Yes |
| Builtin Functions | Yes | Yes |
| Builtin Macros | Yes | Yes |
| C++ Comments: C++ comments are recognized. | Yes | Yes |
| Case Ranges: 'case 1 ... 9' and such. | No | No |
| Cast to Union: Casting to union type from any member of the union. | Yes, with warning | Yes, with warning |
| Character Escapes: You can use \e as ASCII escape. | Yes | Yes |
| Checks for Standard Language Features | Partial: (without c_thread_local); query extension using __has_extension. | Partial: (without c_thread_local); query extension using __has_extension. |
| Checks for Type Traits | No | No |
| Complex Numbers: Data types for complex numbers. | Partial, with warning | Partial, with warning |
| Compound Literals: Give structures, unions or arrays as values. | Yes, with warning | Yes, with warning |
| Concatenation of wide and non-wide character strings | Yes | Yes |
| Conditionals: Omits the middle operand of a ?: expression. | No | No |
| Constant Array Folding: Variable length arrays folded to constant arrays | Yes, with warning | Yes |
| Constraints: Constraints for asm operands. | Partial: All except 'H', 's', ' ', '?', '!', '&', '%', '#', '*'. | Partial: All except 'H', 's', ' ', '?', '!', '&', '%', '#', '*'. |
| Constructing Calls: Dispatching a call to another function. | No | No |
| Decimal Float: Decimal Floating Types. | No | No |
| Designated Inits: Labeling elements of initializers. | Yes, with warning | Yes, with warning |
| Digraphs and Trigraphs | Yes | Yes |
| Dollar Signs: You can use dollar signs in identifiers. | Yes | Yes |
| Duplicate type qualifiers | Yes | Yes |
| Empty Structures: Structures with no members. | Yes, with warning | Yes, with warning |
| Escaped Newlines: Slightly looser rules for escaped newlines. | No, with warning | No, with warning |
| Explicit Register Variables - Store a local variable in a register. | Yes | Yes |
| Extended Asm: Assembler Instructions with C Expression Operands | No | No |
| Extensions for Dynamic Analysis | No | No |
| Extensions for Static Analysis | Partial: Only __noreturn__. | Partial: Only __noreturn__. |
| Feature Checking Macros | Partial: __has_extension not supported. | Partial: __has_extension not supported. |
| Fixed-Point: Fixed-Point Types. | No | No |
| Flexible Array: Members at the end of a structure or union. | Yes, with warning | Yes |
| Floating Types: Additional Floating Types | No | No |
| Format String Checking | Yes | Yes |
| Function Attributes: Declaring that functions have no side effects, or that they can never return. | Yes | Yes |
| Function Names: Printable strings which are the name of the current function. | Yes | Yes |
| Function Overloading in C | Yes | Yes |
| Function Prototypes: Prototype declarations and old-style definitions. | Yes, with warning | Yes, with warning |
| Hex Floats: Hexadecimal floating-point constants. | Yes, with warning | Yes |
| Include File Checking Macros | Yes | Yes |
| Incomplete Enums: enum foo;, with details to follow. | Yes, with warning | Yes, with warning |
| Initializer lists for complex numbers in C | No | No |
| Initializers: Non-constant initializers. | Yes | Yes |
| Inline: Defining inline functions (as fast as macros). | Yes | Yes |
| Integer Constant Expression Folding: Expressions that are folded to integer constants | Yes, with warning | Yes, with warning |
| Labels as Values: Getting pointers to labels, and computed gotos. | No | No |
| Local Labels: Labels local to a block. | No | No |
Long Long: Double-word integers, long long int. |
Yes, with warning | Yes |
| Messages on deprecated and unavailable Attributes | Yes | Yes |
| Mixed Declarations: Mixing declarations and code. | Yes, with warning | Yes |
| Nested Functions: As in Algol and Pascal, lexical scoping of functions. | No | No |
| New limit for #line directive | Yes | Yes |
| Non-standard C++11 Attributes | No | No |
| Object Size Checking: Built-in functions for limited buffer overflow checking. | Yes | Yes |
| Objective-C Features | No | No |
| Offsetof: Special syntax for implementing offsetof. | Yes | Yes |
| Other Builtins: Other built-in functions. | Partial | Partial |
| Pointer Arithmetic: Arithmetic on void-pointers and function pointers. | No | No |
| Pragmas: Pragmas accepted by GCC | Yes | Yes |
| _Pragma preprocessing operator | Yes | Yes |
| Return Address: Getting the return or frame address of a function. | Yes | Yes |
| snprintf family of functions | Yes | Yes |
| Statement Expressions: Putting statements and declarations inside expressions. | No | No |
| Static arrays as function parameters | Yes, with warning | Yes |
| Subscripting: Any array can be subscripted, even if not an lvalue. | Yes | Yes |
| Target Builtins: Built-in functions specific to particular targets. | No | No |
| Target Format Checks: Format checks specific to particular targets. | No | No |
| Target-Specific Extensions | No | No |
| Thread-Local: Per-thread variables. | Yes | Yes |
| Thread-Safety Annotation Checking | No | No |
| Trailing comma allowed in enum declaration | Yes, with warning | Yes |
| Type Attributes: Specifying attributes of types. | Yes | Yes |
| Typeof: typeof, referring to the type of an expression. | No | No |
| Type-generic math | No | No |
| Type Safety Checking | No | No |
| Unnamed Fields: Unnamed struct/union fields within structs/unions. | Yes, with warning | Yes, with warning |
| User-Specified System Frameworks | No | No |
| Variable Attributes: Specifying attributes of variables. | Partial: All except shared and __gcc_struct__. | Partial: aligned attribute supported. |
| Variable Length: Arrays whose length is computed at run time. | Yes, with warning | Yes, with warning |
| Variadic Macros: Macros with a variable number of arguments. | Yes, with warning | Yes |
| Vector Extensions: Using vector instructions through built-in functions. | Yes | Yes |
| Vectors and Extended Vectors | Partial | Partial |
| vscanf family of functions | Yes | Yes |
| Zero Length: Zero-length arrays. | Yes, with warning | Yes, with warning |