gcc Compatibility

C language object files created with the Intel® C++ Compiler are binary compatible with the GNU gcc* compiler and glibc*, the GNU C language library. You can use the Intel compiler or the gcc compiler to pass object files to the linker. However, to correctly pass the Intel libraries to the linker, use the Intel compiler.

The Intel C++ Compiler supports many of the language extensions provided by the GNU compilers.

gcc Extensions to the C Language

GNU C includes several, non-standard features not found in ISO standard C. This version of the Intel C++ Compiler supports most of these extensions listed in the following table. See http://www.gnu.org for more information.

gcc Language Extension	Intel Support
Statements and Declarations in Expressions	Yes
Locally Declared Labels	Yes
Labels as Values	Yes
Nested Functions	Yes
Constructing Function Calls	No
Naming an Expression's Type	Yes
Referring to a Type with typeof	Yes
Generalized Lvalues	Yes
Conditionals with Omitted Operands	Yes
Double-Word Integers	Yes
Complex Numbers	Yes
Hex Floats	Yes
Arrays of Length Zero	Yes
Arrays of Variable Length	Yes
Macros with a Variable Number of Arguments.	Yes
Slightly Looser Rules for Escaped Newlines	No
String Literals with Embedded Newlines	Yes
Non-Lvalue Arrays May Have Subscripts	Yes
Arithmetic on void-Pointers	Yes
Arithmetic on Function-Pointers	Yes
Non-Constant Initializers	Yes
Compound Literals	Yes
Designated Initializers	Yes
Cast to a Union Type	Yes
Case Ranges	Yes
Mixed Declarations and Code	Yes
Declaring Attributes of Functions	Yes
Attribute Syntax	Yes
Prototypes and Old-Style Function Definitions	No
C++ Style Comments	Yes
Dollar Signs in Identifier Names	Yes
ESC Character in Constants	Yes
Specifying Attributes of Variables	Yes
Specifying Attributes of Types	Yes
Inquiring on Alignment of Types or Variables	Yes
Inline Function is As Fast As a Macro	Yes
Assembler Instructions with C Expression Operands	Yes
Controlling Names Used in Assembler Code	Yes
Variables in Specified Registers	Yes
Alternate Keywords	Yes
Incomplete enum Types	Yes
Function Names as Strings	Yes
Getting the Return or Frame Address of a Function	Yes
Using Vector Instructions Through Built-in Functions	No
Other built-in functions provided by GCC	Yes
Built-in Functions Specific to Particular Target Machines	No
Pragmas Accepted by GCC	Yes
Unnamed struct/union fields within structs/unions	Yes
Built-in integer data types, __int128 and __uint128	Yes Note Intel® C++ Compiler supports representation of full __int128 [or int128?] literals.
Decimal floating types	Yes

g++* Extensions to the C++ Language

GNU C++ includes several, non-standard features not found in ISO standard C++. This version of the Intel C++ Compiler supports many of these extensions listed in the following table. See http://www.gnu.org for more information.

g++ Language Extension	Intel Support
Minimum and Maximum operators in C++	Yes
When is a Volatile Object Accessed?	No
Restricting Pointer Aliasing	Yes
Vague Linkage	Yes
Declarations and Definitions in One Header	No
Where's the Template?	extern template supported
Extracting the function pointer from a bound pointer to member function	Yes
C++-Specific Variable, Function, and Type Attributes	Yes Note The Intel® C++ Compiler is now compatible with gcc v4.5.
Java Exceptions	No
Deprecated Features	No
Backwards Compatibility	No

Note

Statement expressions are supported, except the following are prohibited inside them:

dynamically-initialized local static variables
local non-POD class definitions
try/catch
variable length arrays

Also, branching out of a statement expression and statement expressions in constructor initializers are not allowed. Variable-length arrays are no longer allowed in statement expressions.

Note

The Intel C++ Compiler supports gcc-style inline ASM if the assembler code uses AT&T* System V/386 syntax.