smolbasic55

smolbasic55 is at least a ECMA-55 Minimal BASIC compiler.

Features

• Assembles to RISC-V or AMD64.
• Full ECMA-55 Minimal BASIC.
• Non-standard features are available.

Usage

smolbasic55 [FEATURES] FILE.BAS OUTPUT.S

The generated assembly may need to be linked against the C files data.c, array.c, input.c, print.c, control.c, string.c, math.c, depending on your code.

FEATURES are enabled with +FEATURE and disabled with -FEATURE. If FEATURE does not start with NO, NOFEATURE inverts the feature.

• NOEND allow missing END.
• FULLDEF make DEF more powerful (see below).
• EXTERN every function call that is neither user-defined nor builtin is treated as an external call (see below).
• TYPE add type suffixes (see below).
• PTR add untyped pointer casts (see below).
• INLINE any line that does not start with a (line) number is pasted verbatim into the assembly output.

Feature flags can also be set in a file with 10 OPTION FLAGS ... (should be the first line number).

Option FULLDEF

If FULLDEF is set, user-defined functions can:

1. Have multiple arguments.
2. Have string arguments.
3. Return strings (e.g. DEF FNA$(X$)=X$).

Option EXTERN

If EXTERN is set:

1. SOMEFUN(...) in an expression translates to an external call that returns a floating-point number.
2. SOMEFUN$(...) in an expression translates to an external call that returns a string.
3. CALL NAME(...) translates to an external call.

Option TYPE

If TYPE is set:

1. Variables, numbers and functions (if FULLDEF or EXTERN is set) can include the following suffixes:
   • ~ to indicate a C char.
   • % to indicate a C short.
   • | to indicate a C int.
   • & to indicate a C long.
   • @ to indicate a C void* (i.e. an unsigned integer type with the same width as a pointer).
   • ! to indicate a C float (or the smallest floating-point type natively supported).
2. The CAST function casts its argument to the function type (e.g. CAST~(123&) casts a long to a char).

Many functions promote their arguments to the greatest type, rendering certain casts as no-ops. For example, PRINT CAST~(500), 500~ will print 500 twice, even though 500 would not fit in a byte.

Option PTR

If PTR is set:

1. PTR(Var) returns a pointer to a variable.
2. DEREF(Pointer) dereferences a pointer. The type of the function determines the type of the cast.

Linking

External functions have the following naming scheme in the generated assembly code:

• The name of the function (without type suffixes).
• If type is string, $.
• If type is enabled by TYPE, add a type character after $.

If arguments are provided:

• Two underscores (__).
• For every argument:
  • If argument is (double) floating-point, d.
  • If argument is string, S.
  • If TYPE is set:
    • If argument is (single) floating-point, f.
    • If argument is byte, c.
    • If argument is short, s.
    • If argument is integer, i.
    • If argument is long, l.
    • If argument is a pointer, p.

Tests

Test files were mostly taken from bas55.

Licence

This work is licenced under the EUPL-1.2.