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Port the BASIC interpreter from Go to C

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Reproduces deps/basicinterpret in C, in the idiom of the ak* libraries. All 41
.bas files in the reference's corpus produce byte-identical stdout, including
the trailing double newline on an error line -- that comes from basicError
building a string ending in \n and handing it to Println, and
array_outofbounds.txt encodes it.

The corpus is driven in place from the submodule as 41 individual CTest cases
rather than copied, so it cannot drift from upstream. Eighteen unit tests cover
what the corpus cannot reach.

Three structural changes carry most of the work. Go's three reflection lookups
(Command*, Function*, ParseCommand*) become one sorted dispatch table in
src/verbs.c searched with bsearch; adding a verb is a row and two functions. The
five Go maps become one fixed open-addressed table over aksl_strhash_djb2. And
run(), which owned the process until MODE_QUIT, splits into step() plus a
bounded run() -- goal 3 requires a host game to be able to bound execution, and
nothing in the library now terminates the process or touches SDL.

Output goes through an akbasic_TextSink vtable. src/sink_stdio.c is what makes
the corpus runnable with no SDL present; the akgl-backed sink is still to come
and is blocked on libakgl having no text-measurement call.

src/convert.c exists because libakstdlib's aksl_ato* family cannot report a
conversion failure (its TODO.md 2.1.5). The reference checks strconv's error at
four sites and turns it into a BASIC error; routing those through aksl_atoi
would have turned four diagnosable errors into wrong answers, with VAL("garbage")
quietly returning 0. TODO.md 1.9 records which libakstdlib calls are cleared for
use here and which are not.

Reference defects are reproduced, not fixed: the golden files encode the observed
behaviour and a silent correction is a behaviour change. TODO.md section 6 lists
sixteen, and tests/known_reference_defects.c asserts the *correct* contract for
six of them under AKBASIC_KNOWN_FAILING_TESTS, so a fix shows up as
"unexpectedly passed". Five of the sixteen were found by this port and are new:
subtraction stops after one operator so 1-2-3 computes 1-2 and abandons the rest
of the line (a wrong answer, not a refused one); a unary-minus argument inflates
a function's arity so ABS(-9) is rejected; a comparison operator in a line's
final column is dropped; hex literals never survive the scanner; and the
"Reserved word in variable name" check is dead code.

Where the reference reaches undefined behaviour by a route that is defined in Go
-- an out-of-range shift, a negative string multiplier, integer division by zero
-- this raises instead of inheriting the UB. No golden case exercises any of
them.

The top-level CMakeLists shadows add_test, set_tests_properties and
add_custom_target around all three add_subdirectory calls. Without it libakerror's
tests land in our suite as Not Run, and its un-namespaced `coverage` target stops
a coverage build from configuring at all. Test targets are akbasic_test_<name>:
bare test_<name> collides with libakstdlib's, which is what broke libakgl's
configure in c2b16d3.

ctest 59/59; ASan+UBSan 59/59; 92.3% line and 96.9% function coverage; no
warnings under -Wall -Wextra. Branch coverage is not a target, for the reason
libakstdlib and libakgl both record: the akerror macros expand into large branch
trees at every call site.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Andrew Kesterson
2026-07-30 23:53:56 -04:00
commit f8c15c2f2c
60 changed files with 10192 additions and 0 deletions
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143
tests/runtime_evaluate.c Normal file
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/**
* @file runtime_evaluate.c
* @brief Tests the evaluator against hand-built and hand-parsed trees.
*/
#include "harness.h"
/* Parse an expression-bearing line and evaluate what it produced. */
static akerr_ErrorContext AKERR_NOIGNORE *eval_line(const char *line, akbasic_Value **dest)
{
PREPARE_ERROR(errctx);
akbasic_ASTLeaf *leaf = NULL;
PASS(errctx, akbasic_environment_zero(HARNESS_RUNTIME.environment));
PASS(errctx, harness_parse(line, &leaf));
PASS(errctx, akbasic_runtime_evaluate(&HARNESS_RUNTIME, leaf, dest));
SUCCEED_RETURN(errctx);
}
static void expect_int(const char *line, int64_t want)
{
akbasic_Value *out = NULL;
akerr_ErrorContext *e = eval_line(line, &out);
if ( e != NULL ) {
fprintf(stderr, "FAIL: \"%s\": %s\n", line, e->message);
akbasic_test_failures += 1;
test_discard_error(e);
return;
}
TEST_REQUIRE(out->valuetype == AKBASIC_TYPE_INTEGER,
"\"%s\" produced type %d, expected integer", line, (int)out->valuetype);
TEST_REQUIRE(out->intval == want,
"\"%s\" produced %lld, expected %lld",
line, (long long)out->intval, (long long)want);
}
static void expect_bool(const char *line, bool want)
{
akbasic_Value *out = NULL;
akerr_ErrorContext *e = eval_line(line, &out);
if ( e != NULL ) {
fprintf(stderr, "FAIL: \"%s\": %s\n", line, e->message);
akbasic_test_failures += 1;
test_discard_error(e);
return;
}
TEST_REQUIRE(akbasic_value_is_true(out) == want,
"\"%s\" expected %s", line, (want ? "true" : "false"));
}
int main(void)
{
akbasic_Value *out = NULL;
akerr_ErrorContext *e = NULL;
TEST_REQUIRE_OK(harness_start(NULL));
/* Literals and arithmetic. */
expect_int("A# = 42", 42);
expect_int("A# = 1 + 2 * 3", 7);
expect_int("A# = (1 + 2) * 3", 9);
expect_int("A# = -5 + 10", 5);
expect_int("A# = 8 / 2", 4);
/* Identifiers read back what was assigned. */
expect_int("A# = 7", 7);
expect_int("B# = A# + 1", 8);
/*
* Comparisons yield BASIC booleans. They are evaluated bare rather than
* assigned: assign() accepts only INTEGER or FLOAT into a `#` variable, so
* `A# = 1 == 1` is "Incompatible types in variable assignment" -- which is
* also why IF works on the comparison directly and never through a variable.
*
* They are wrapped in parens because a bare leading integer in token
* position 0 is consumed as a *line number*, not as a literal.
*/
expect_bool("(1 == 1)", true);
expect_bool("(1 == 2)", false);
expect_bool("(2 > 1)", true);
expect_bool("(1 <> 2)", true);
TEST_REQUIRE_OK(akbasic_environment_zero(HARNESS_RUNTIME.environment));
TEST_REQUIRE_STATUS(eval_line("A# = 1 == 1", &out), AKBASIC_ERR_TYPE);
/* Bitwise operators. */
expect_int("A# = 12 AND 10", 8);
expect_int("A# = 12 OR 10", 14);
/* Arrays: assign through a subscript and read it back. */
{
akbasic_ASTLeaf *leaf = NULL;
TEST_REQUIRE_OK(akbasic_environment_zero(HARNESS_RUNTIME.environment));
TEST_REQUIRE_OK(harness_parse("DIM C#(4)", &leaf));
TEST_REQUIRE_OK(akbasic_runtime_evaluate(&HARNESS_RUNTIME, leaf, &out));
}
expect_int("C#(2) = 99", 99);
expect_int("D# = C#(2)", 99);
expect_int("D# = C#(0)", 0);
/* An out-of-bounds subscript raises with the reference's message. */
TEST_REQUIRE_OK(akbasic_environment_zero(HARNESS_RUNTIME.environment));
e = eval_line("D# = C#(9)", &out);
TEST_REQUIRE(e != NULL, "an out-of-bounds read must raise");
if ( e != NULL ) {
TEST_REQUIRE_STR(e->message,
"Variable index access out of bounds at dimension 0: 9 (max 3)");
test_discard_error(e);
}
/*
* Built-in functions dispatch through the table.
*
* Note the arguments are never negative *literals*: a unary-minus leaf uses
* its .right for the operand, and the parser counts arity by walking .right,
* so `ABS(-9)` reports two arguments and is rejected. TODO.md section 12
* item 13. The golden corpus sidesteps it the same way -- sgn.bas assigns
* -1 to a variable first.
*/
expect_int("N# = -9", -9);
expect_int("A# = ABS(N#)", 9);
expect_int("A# = SGN(N#)", -1);
expect_int("A# = LEN(\"HELLO\")", 5);
expect_int("A# = SHL(1, 4)", 16);
expect_int("A# = SHR(16, 4)", 1);
expect_int("A# = XOR(12, 10)", 6);
expect_int("A# = MOD(7, 3)", 1);
expect_int("A# = INSTR(\"HELLO\", \"LL\")", 2);
expect_int("A# = INSTR(\"HELLO\", \"ZZ\")", -1);
/* An unknown verb is diagnosed rather than silently ignored. */
TEST_REQUIRE_OK(akbasic_environment_zero(HARNESS_RUNTIME.environment));
TEST_REQUIRE_STATUS(akbasic_runtime_evaluate(&HARNESS_RUNTIME, NULL, &out),
AKERR_NULLPOINTER);
/* A label resolves to its line number through a bare identifier. */
TEST_REQUIRE_OK(akbasic_environment_set_label(HARNESS_RUNTIME.environment, "TOP", 30));
expect_int("A# = TOP", 30);
harness_stop();
return akbasic_test_failures;
}