WPCC Internals

WPCC uses the GNU Preprocessor, Assembler, and Linker. It does not use the "C" compiler (or any other high-level language components). The provided make rules do, however, use the "gcc" wrapper for these components.

Most of the functionality is provided by a set of preprocessor macros that transform various tasks into assembler directives. These directives organize various bits of information in ELF sections that are later processed by a custom linker script into Wang program images.

The following sections are generated for Wang 600 code, with similar equivalents for the Wang 700:

.wang600label

Abstract. Allocation of labels for nun-subroutine (non-f(x)) use.

.wang600flabel

Abstract. Allocation of labels for subroutine (f(x)) use.

.wang600data

Loaded. Register data. Aligned on 8-byte boundaries*.

.wang600code

Loaded. Program codes, and references to labels and data (long registers).

.wang600dummy

Abstract. Used to calculate end of program codes to facilitate assignment of long register space. Each byte of program code gets a "shadow" byte in this section.

.wang600regs

Abstract. Allocation of labels for long (extended) registers.

.wang600search

.wang600call

.wang600subr

Abstract. Used to delay assignment of actual SEARCH, CALL, and f(x)/F(x) command codes until link time, when it is known whether the target label is in ROM or RAM. The Wang 700 does not use these, except for the "subr" section which is used to generate the actual subroutine call code.

* The Wang 700 stores register in memory as pairs of registers with the data interlaced, high 4 bits belonging to one register and low 4 bits to the other.

In order to facilitate control over function ordering (assignment of function codes), the sections ".wang600flabel" and ".wang600subr" will have the name of the subroutine (the symbolic label assigned by the programmer) appended to the section name, for example ".wang600flabel.foo".

Special linker scripts process the above sections into executable Wang 600 program codes. There are currently two linker scripts, T_LDSCRIPT (wang600raw.ld) for making Tape image programs, and X_LDSCRIPT (wang600rawrom.ld) for making Expansion ROM (library) images (The Wang 700 only has one linker script).

These linker scripts INCLUDE scripts names "fnordering1.ld" and "fnordering2.ld" in the processing of sections ".wang600flabel" and ".wang600subr" (respectively). The default copy of these files (in /usr/local/wpcc) are empty. If a compile involves function ordering (FORDERED() directives) then local versions of these files are created temporarely, for use in the link phase of the target program. The output produced by the FORDERED() directives is processed into linker scripts (and the function key label file).

Note, standard library "archives" (lib*.a) may be produced independent of the final type of image. A program may be linked with a library (i.e. "static linking") or may be linked against a ROM image (sort of like "dynamic linking"). Note, however, that there is no way for the Wang 600 to ensure that a program linked against a ROM image is being run with the correct ROM image installed.

Similar sections are used for Wang 700 programs, although "call" does not apply. Also, the Wang 700 did not support Expansion ROMs and so no provisions are made for linking programs or modules into an Expansion ROM image.

There is also a file "wang600opcodes.s" that is used to provide the opcode values for program codes. There are also a few miscellaneous constants defined there to aid in abstracting other utilities. This file is converted into a header file (wang600opcodes.h) automatically for use by C utilities.

TODO: Support combining programs (and data) into a Model 630/730 Disk image.