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To use any of these supported distributions, the directory containing the GCC executable must be included in the $PATH environment variable.

Tip

Tip

In some versions of CygwinTM (for Windows), it is possible to have GCC 2.95.x and GCC 3.x installed at the same time. This is because there are two differently-named executables for GCC 2.95.x and GCC 3.x, so both of them can be located on the $PATH and both will be detected by C++test.

Unsupported Compiler Extensions for GCC Compilers

...

These limitations also apply to appropriate versions of GCC-based cross-compilers listed in Supported Compilers, other GCC-based cross-compilers, and custom GCC compiler builds.

GCC 2.95.x

Unsupported Features

  • Arrays of Variable Length as Arguments to Functions

    Code Block
    void tester (int len, char data[len][len])
{
}

    Complex Numbers

  • Nested Functions
  • Named Return Values

  • Virtual Functions With Overridden Return Types

    Code Block
    class A
{
	public:
		virtual void* a();
};
class B:
	public A
{
	public:
		virtual B* a(); // Return type changed from void* to
			(compatible) B*.
};

Incompatibilities

  • Function Attributes

    Code Block
    void fatal () __attribute__ ((noreturn));
void fatal () { }
typedef void voidfn ();
volatile voidfn fatal;
  "void fatal()"

  • Member Access Checking

    Code Block
    class A
{
	public:
		void pub_func();
	protected:
		void prot_func();
};
class B : public A
{
	public:
		void foo()
		{
			&A::prot_func;
		}
};

GCC 3.2.x

Unsupported Features

  • Arrays of Variable Length as Arguments to Functions

    Code Block
    void tester (int len, char data[len][len])
{
}
  • Complex Numbers
  • Nested Functions
  • Named Return Values

  • Virtual Functions With Overridden Return Types

    Code Block
    class A
{
	public:
		virtual void* a();
};
class B:
	public A
{
	public:
		virtual B* a(); // Return type changed from void* to
			(compatible) B*.
};
  • Java Extensions (like extern "Java", java attributes)

  • Restricting Pointer Aliasing for Member Functions

    Code Block
    class T
{
	public:
		void fn();
};
void T::fn () __restrict__
{
}

Incompatibilities

  • Function Attributes

    Code Block
    void fatal () __attribute__ ((noreturn));
void fatal () { }
typedef void voidfn ();
volatile voidfn fatal;
 "void fatal()"

  • Member Access Checking

    Code Block
     class A
{
	public:
		void pub_func();
	protected:
		void prot_func();
};
class B : public A
{
	public:
		void foo()
		{
			&A::prot_func;
		}
};

  • Attributes After Declarator

    Code Block
    class X
{
	public:
		X(int) {}
};
X x(1) __attribute__((aligned (16)));

...

.

...

Unsupported Features

  • Arrays of Variable Length as Arguments to Functions

    Code Block
     void tester (int len, char data[len][len])
{
}
  • Complex Numbers
  • Nested Functions
  • Named Return Values

  • Virtual Functions With Overridden Return Types

    Code Block
     class A
{
	public:
		virtual void* a();
};
class B:
	public A
{
	public:
		virtual B* a(); // Return type changed from void* to
			(compatible) B*.
};
  • Java Extensions (like extern "Java", java attributes)

  • Restricting Pointer Aliasing for Member Functions

    Code Block
     class T
{
	public:
		void fn();
};
void T::fn () __restrict__
{
}

Incompatibilities

  • Function Attributes

    Code Block
    void fatal () __attribute__ ((noreturn));
void fatal () { }
typedef void voidfn ();
volatile voidfn fatal;

  • Member Access Checking

    Code Block
    class A
{
public:
void pub_func();
protected:
void prot_func();
};
class B : public A
{
public:
void foo()
{
&A::prot_func;
}
};

  • Attributes After Declarator

    Code Block
    class X
{
public:
X(int) {}
};
X x(1) __attribute__((aligned (16)));

GCC 3.4.x

Unsupported Features

  • Arrays of Variable Length as Arguments to Functions

    Code Block
    void tester (int len, char data[len][len])
{
}
  • Complex Numbers
  • Nested Functions
  • Named Return Values

  • Virtual Functions With Overridden Return Types

    Code Block
    class A
{
	public:
		virtual void* a();
};
class B:
	public A
{
	public:
		virtual B* a(); // Return type changed from void* to
			(compatible) B*.
};
  • Java Extensions (like extern "Java", java attributes)

  • Restricting Pointer Aliasing for Member Functions

    Code Block
    class T
{
	public:
		void fn();
};
void T::fn () __restrict__
{
}

Incompatibilities

Function Attributes

...

GCC 4.0.x

Unsupported Features

  • Arrays of Variable Length as Arguments to Functions

    Code Block
    void tester (int len, char data[len][len])
{
}
  • Complex Numbers
  • Nested Functions

  • Virtual Function With Overridden Return Type

    Code Block
    class A
{
	public:
		virtual void* a();
};
class B:
	public A
{
	public:
		virtual B* a(); // Return type changed from void* to (compatible) B*.
			// It is ok in GCC but EDG will complain
};
  • Java Extensions (like extern "Java", java attributes)
  • Offsetof extension

  • Restricting Pointer Aliasing for Member functions

    Code Block
    class T
{
	public:
		void fn();
};
void T::fn () __restrict__ // EDG won't compile this
{
}

Incompatibilities

  • Function Attributes

    Code Block
    void fatal () __attribute__ ((noreturn));
void fatal () { }
typedef void voidfn ();
volatile voidfn fatal; // EDG: declaration is incompatible with
// "void fatal()"

  • Friend Declarations

    Code Block
    class A;
namespace N {
	class B {
		friend class A; // In GCC 4.0+ it refer to N::A (which has not been
			// declared yet) But EDG and older GCCs refer to ::A
		int _private;
};
	class A {
		void foo()
		{
			B b;
			b._private = 0; // EDG inaccessible field.
		}
	};
}

...