5.3 Proposed Extensions

Here's a list of proposed extensions for gfortran, in no particular order. Most of these are necessary to be fully compatible with existing Fortran compilers, but they are not part of the official J3 Fortran 95 standard.

5.3.1 Compiler extensions:

• Flag for defining the kind number for default logicals.
• User-specified alignment rules for structures.
• Flag to generate Makefile info.
• Automatically extend single precision constants to double.
• Compile code that conserves memory by dynamically allocating common and module storage either on stack or heap.
• Flag to cause the compiler to distinguish between upper and lower case names. The Fortran 95 standard does not distinguish them.
• Compile flag to generate code for array conformance checking (suggest -CC).
• User control of symbol names (underscores, etc).
• Compile setting for maximum size of stack frame size before spilling parts to static or heap.
• Flag to force local variables into static space.
• Flag to force local variables onto stack.
• Flag to compile lines beginning with “D”.
• Flag to ignore lines beginning with “D”.
• Flag for maximum errors before ending compile.
• Generate code to check for null pointer dereferences – prints locus of dereference instead of segfaulting. There was some discussion about this option in the g95 development mailing list.
• Allow setting the default unit number.
• Option to initialize otherwise uninitialized integer and floating point variables.
• Support for OpenMP directives. This also requires support from the runtime library and the rest of the compiler.
• Support for Fortran 200x. This includes several new features including floating point exceptions, extended use of allocatable arrays, C interoperability, Parameterizer data types and function pointers.

5.3.2 Environment Options

• Pluggable library modules for random numbers, linear algebra. LA should use BLAS calling conventions.
• Environment variables controlling actions on arithmetic exceptions like overflow, underflow, precision loss – Generate NaN, abort, default. action.
• Set precision for fp units that support it (i387).
• Variable for setting fp rounding mode.
• Variable to fill uninitialized variables with a user-defined bit pattern.
• Environment variable controlling filename that is opened for that unit number.
• Environment variable to clear/trash memory being freed.
• Environment variable to control tracing of allocations and frees.
• Environment variable to display allocated memory at normal program end.
• Environment variable for filename for * IO-unit.
• Environment variable for temporary file directory.
• Environment variable forcing standard output to be line buffered (unix).