Compiler

The Digital UNIX Version 4.0 C compiler was designed to support 64-bit data types and is NIST-validated for compliance with the ANSI Standard for C. The C front end supports both 64-bit addressing and the interfaces to the System V shared libraries.

The GEM-based DEC C compiler, accessed optionally in previous releases through the -migrate switch, is now the default compiler; access to the older MIPS-based compiler is still available through the -oldc switch on the cc and c89 command lines.

DEC C uses Digital's backend compiler technology (GEM), which has been specifically developed and optimized for use with Alpha systems. Both compilers have full binary compatibility with each other.

In addition, the compiler:

• Compiles C dialects of user choice including:

  • K&R C (-std0 mode)

  • Strict ANSI C (-std1 mode)

  • ANSI C with extensions (-std mode)

• Supports the XPG4-UNIX standard

  • By default, under the c89 command

  • With the -D_XOPEN_SOURCE_EXTENDED option to cc.

    For more information on the various standards supported by Digital UNIX, see the standards(5) manpage.

• Supports floating point/double precision operations in the following two modes:

  • IEEE support (including proper handling for exceptional conditions like NaN, INF, and so forth)

  • Fast Math mode (INF, NaN, and so forth, translated to avoid exception handling)

• Supports the following language extensions:

  • C++ style structured exception handling by using try...except and termination handling using try...finally

  • User-defined assembly language sequences using asm sequences

  • 32-bit pointers to help reduce the amount of memory used by dynamically allocated pointers, and to facilitate the porting of 64-bit hostile programs

  • Linking programs in 32-bit address space to facilitate the porting of 64-bit hostile programs

  • Pragmas for controlling alignment of structures

For more information on the Digital UNIX C compiler, see the cc(1) reference page.