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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>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
This commit is contained in:
Tachikoma
2026-07-30 23:53:56 -04:00
commit 4e188b2794
60 changed files with 10192 additions and 0 deletions
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src/environment.c Normal file
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/**
* @file environment.c
* @brief Implements the scope and per-line working state.
*/
#include <inttypes.h>
#include <string.h>
#include <akerror.h>
#include <akbasic/environment.h>
#include <akbasic/error.h>
#include <akbasic/runtime.h>
akerr_ErrorContext *akbasic_environment_init(akbasic_Environment *obj, akbasic_Runtime *runtime, akbasic_Environment *parent)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL environment in init");
FAIL_ZERO_RETURN(errctx, (runtime != NULL), AKERR_NULLPOINTER, "NULL runtime in environment init");
PASS(errctx, akbasic_symtab_init(&obj->variables, AKBASIC_MAX_VARIABLES));
PASS(errctx, akbasic_symtab_init(&obj->functions, AKBASIC_MAX_FUNCTIONS));
PASS(errctx, akbasic_symtab_init(&obj->labels, AKBASIC_MAX_LABELS));
obj->parent = parent;
obj->runtime = runtime;
obj->forNextVariable = NULL;
obj->forStepLeaf = NULL;
obj->forToLeaf = NULL;
obj->loopFirstLine = 0;
obj->loopExitLine = 0;
obj->gosubReturnLine = 0;
obj->readReturnLine = 0;
obj->readIdentifierIdx = 0;
obj->waitingForCommand[0] = '\0';
obj->errorToken = NULL;
memset(obj->readIdentifierLeaves, 0, sizeof(obj->readIdentifierLeaves));
obj->readLeafPool.next = 0;
obj->readLeafPool.capacity = AKBASIC_MAX_LEAVES;
obj->readLeafPool.leaves = obj->readLeafStorage;
PASS(errctx, akbasic_value_zero(&obj->forStepValue));
PASS(errctx, akbasic_value_zero(&obj->forToValue));
PASS(errctx, akbasic_value_zero(&obj->returnValue));
if ( obj->parent != NULL ) {
obj->lineno = obj->parent->lineno;
obj->nextline = obj->parent->nextline;
} else {
obj->lineno = 0;
obj->nextline = 0;
}
obj->nextvalue = 0;
PASS(errctx, akbasic_environment_zero_parser(obj));
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_zero(akbasic_Environment *obj)
{
PREPARE_ERROR(errctx);
int i = 0;
FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL environment in zero");
for ( i = 0; i < AKBASIC_MAX_VALUES; i++ ) {
PASS(errctx, akbasic_value_init(&obj->values[i]));
}
obj->nextvalue = 0;
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_zero_parser(akbasic_Environment *obj)
{
PREPARE_ERROR(errctx);
int i = 0;
FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL environment in zero_parser");
for ( i = 0; i < AKBASIC_MAX_LEAVES; i++ ) {
PASS(errctx, akbasic_leaf_init(&obj->leaves[i], AKBASIC_LEAF_UNDEFINED));
}
for ( i = 0; i < AKBASIC_MAX_TOKENS; i++ ) {
PASS(errctx, akbasic_token_init(&obj->tokens[i]));
}
obj->curtoken = 0;
obj->nexttoken = 0;
obj->nextleaf = 0;
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_new_value(akbasic_Environment *obj, akbasic_Value **dest)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL && dest != NULL), AKERR_NULLPOINTER,
"NULL argument in new_value");
FAIL_ZERO_RETURN(errctx, (obj->nextvalue < AKBASIC_MAX_VALUES), AKBASIC_ERR_BOUNDS,
"Maximum values per line reached");
*dest = &obj->values[obj->nextvalue];
obj->nextvalue += 1;
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_new_leaf(akbasic_Environment *obj, akbasic_ASTLeaf **dest)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL && dest != NULL), AKERR_NULLPOINTER,
"NULL argument in new_leaf");
FAIL_ZERO_RETURN(errctx, (obj->nextleaf < AKBASIC_MAX_LEAVES), AKBASIC_ERR_BOUNDS,
"No more leaves available");
*dest = &obj->leaves[obj->nextleaf];
obj->nextleaf += 1;
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_wait_for_command(akbasic_Environment *obj, const char *command)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL && command != NULL), AKERR_NULLPOINTER,
"NULL argument in wait_for_command");
/*
* The reference panics here. An interpreter library may not take the process
* with it, so this raises instead -- but it is still a hard failure, because
* two pending waits in one environment means the block structure is already
* corrupt.
*/
FAIL_NONZERO_RETURN(errctx, (obj->waitingForCommand[0] != '\0'), AKBASIC_ERR_STATE,
"Can't wait on multiple commands in the same environment : %s",
obj->waitingForCommand);
FAIL_ZERO_RETURN(errctx, (strlen(command) < sizeof(obj->waitingForCommand)),
AKBASIC_ERR_BOUNDS, "Command name '%s' is too long to wait on", command);
strncpy(obj->waitingForCommand, command, sizeof(obj->waitingForCommand) - 1);
obj->waitingForCommand[sizeof(obj->waitingForCommand) - 1] = '\0';
SUCCEED_RETURN(errctx);
}
bool akbasic_environment_is_waiting_for_any(akbasic_Environment *obj)
{
if ( obj == NULL ) {
return false;
}
if ( obj->waitingForCommand[0] != '\0' ) {
return true;
}
return akbasic_environment_is_waiting_for_any(obj->parent);
}
bool akbasic_environment_is_waiting_for(akbasic_Environment *obj, const char *command)
{
if ( obj == NULL || command == NULL ) {
return false;
}
if ( strcmp(obj->waitingForCommand, command) == 0 ) {
return true;
}
return akbasic_environment_is_waiting_for(obj->parent, command);
}
akerr_ErrorContext *akbasic_environment_stop_waiting(akbasic_Environment *obj, const char *command)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL && command != NULL), AKERR_NULLPOINTER,
"NULL argument in stop_waiting");
/*
* The reference ignores `command` and clears unconditionally, which lets an
* inner block clear an outer block's wait (TODO.md section 12 item 3). The
* argument is honoured here only to the extent of walking to the environment
* that is actually waiting for it -- clearing the wrong one outright would
* change observable control flow, so the search stops at the first match and
* a miss is silently tolerated, exactly as today.
*/
while ( obj != NULL ) {
if ( strcmp(obj->waitingForCommand, command) == 0 ) {
obj->waitingForCommand[0] = '\0';
SUCCEED_RETURN(errctx);
}
obj = obj->parent;
}
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_get_function(akbasic_Environment *obj, const char *fname, void **dest)
{
PREPARE_ERROR(errctx);
char upper[AKBASIC_SYMTAB_MAX_KEY];
size_t i = 0;
size_t len = 0;
FAIL_ZERO_RETURN(errctx, (obj != NULL && fname != NULL && dest != NULL), AKERR_NULLPOINTER,
"NULL argument in get_function");
len = strlen(fname);
FAIL_ZERO_RETURN(errctx, (len < sizeof(upper)), AKERR_KEY, "Function '%s' is not defined", fname);
for ( i = 0; i < len; i++ ) {
char c = fname[i];
upper[i] = (char)((c >= 'a' && c <= 'z') ? (c - 'a' + 'A') : c);
}
upper[len] = '\0';
while ( obj != NULL ) {
akerr_ErrorContext *found = akbasic_symtab_get(&obj->functions, upper, dest, NULL);
if ( found == NULL ) {
SUCCEED_RETURN(errctx);
}
found->handled = true;
IGNORE(akerr_release_error(found));
obj = obj->parent;
}
FAIL_RETURN(errctx, AKERR_KEY, "Function '%s' is not defined", fname);
}
akerr_ErrorContext *akbasic_environment_get_label(akbasic_Environment *obj, const char *label, int64_t *dest)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL && label != NULL && dest != NULL), AKERR_NULLPOINTER,
"NULL argument in get_label");
while ( obj != NULL ) {
akerr_ErrorContext *found = akbasic_symtab_get(&obj->labels, label, NULL, dest);
if ( found == NULL ) {
SUCCEED_RETURN(errctx);
}
found->handled = true;
IGNORE(akerr_release_error(found));
obj = obj->parent;
}
FAIL_RETURN(errctx, AKBASIC_ERR_UNDEFINED,
"Unable to find or create label %s in environment", label);
}
akerr_ErrorContext *akbasic_environment_set_label(akbasic_Environment *obj, const char *label, int64_t value)
{
PREPARE_ERROR(errctx);
FAIL_ZERO_RETURN(errctx, (obj != NULL && label != NULL), AKERR_NULLPOINTER,
"NULL argument in set_label");
/* Only the top-level environment creates labels. */
while ( obj != NULL && obj->runtime->environment != obj ) {
obj = obj->parent;
}
FAIL_ZERO_RETURN(errctx, (obj != NULL), AKBASIC_ERR_ENVIRONMENT,
"Unable to create label in orphaned environment");
PASS(errctx, akbasic_symtab_set(&obj->labels, label, NULL, value));
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_get(akbasic_Environment *obj, const char *varname, akbasic_Variable **dest)
{
PREPARE_ERROR(errctx);
akbasic_Environment *walk = NULL;
akbasic_Variable *variable = NULL;
int64_t sizes[1] = { 1 };
void *slot = NULL;
FAIL_ZERO_RETURN(errctx, (obj != NULL && varname != NULL && dest != NULL), AKERR_NULLPOINTER,
"NULL argument in environment get");
*dest = NULL;
for ( walk = obj; walk != NULL; walk = walk->parent ) {
akerr_ErrorContext *found = akbasic_symtab_get(&walk->variables, varname, &slot, NULL);
if ( found == NULL ) {
*dest = (akbasic_Variable *)slot;
SUCCEED_RETURN(errctx);
}
found->handled = true;
IGNORE(akerr_release_error(found));
}
/*
* Parents do not create variables for their children: only the currently
* active environment auto-creates. A miss anywhere else returns NULL without
* error, which the caller is expected to notice.
*/
if ( obj->runtime->environment != obj ) {
SUCCEED_RETURN(errctx);
}
PASS(errctx, akbasic_runtime_new_variable(obj->runtime, &variable));
FAIL_ZERO_RETURN(errctx, (strlen(varname) < sizeof(variable->name)), AKBASIC_ERR_BOUNDS,
"Variable name '%s' is too long", varname);
strncpy(variable->name, varname, sizeof(variable->name) - 1);
variable->name[sizeof(variable->name) - 1] = '\0';
variable->valuetype = AKBASIC_TYPE_UNDEFINED;
variable->mutable_ = true;
PASS(errctx, akbasic_variable_init(variable, &obj->runtime->valuepool, sizes, 1));
PASS(errctx, akbasic_symtab_set(&obj->variables, varname, variable, 0));
*dest = variable;
SUCCEED_RETURN(errctx);
}
/*
* Evaluate an lvalue's subscript list, if it has one, into `subscripts`. A bare
* identifier yields the single subscript {0}, which is how a scalar is addressed
* -- every variable is really a one-element array.
*/
static akerr_ErrorContext *collect_subscripts(akbasic_Environment *obj, akbasic_ASTLeaf *lval, int64_t *subscripts, int *count)
{
PREPARE_ERROR(errctx);
akbasic_ASTLeaf *expr = NULL;
akbasic_Value *tval = NULL;
*count = 0;
if ( lval->right != NULL &&
lval->right->leaftype == AKBASIC_LEAF_ARGUMENTLIST &&
lval->right->operator_ == AKBASIC_TOK_ARRAY_SUBSCRIPT ) {
for ( expr = lval->right->right; expr != NULL; expr = expr->right ) {
FAIL_ZERO_RETURN(errctx, (*count < AKBASIC_MAX_ARRAY_DEPTH), AKBASIC_ERR_BOUNDS,
"More than %d array subscripts", AKBASIC_MAX_ARRAY_DEPTH);
PASS(errctx, akbasic_runtime_evaluate(obj->runtime, expr, &tval));
FAIL_NONZERO_RETURN(errctx, (tval->valuetype != AKBASIC_TYPE_INTEGER),
AKBASIC_ERR_TYPE,
"Array dimensions must evaluate to integer (B)");
subscripts[*count] = tval->intval;
*count += 1;
}
}
if ( *count == 0 ) {
subscripts[0] = 0;
*count = 1;
}
SUCCEED_RETURN(errctx);
}
akerr_ErrorContext *akbasic_environment_assign(akbasic_Environment *obj, akbasic_ASTLeaf *lval, akbasic_Value *rval, akbasic_Value **dest)
{
PREPARE_ERROR(errctx);
akbasic_Variable *variable = NULL;
int64_t subscripts[AKBASIC_MAX_ARRAY_DEPTH];
int subscriptcount = 0;
akbasic_Value *slot = NULL;
FAIL_ZERO_RETURN(errctx, (obj != NULL && lval != NULL && rval != NULL && dest != NULL),
AKERR_NULLPOINTER, "nil pointer");
PASS(errctx, akbasic_environment_get(obj, lval->identifier, &variable));
FAIL_ZERO_RETURN(errctx, (variable != NULL), AKBASIC_ERR_UNDEFINED,
"Identifier %s is undefined", lval->identifier);
PASS(errctx, collect_subscripts(obj, lval, subscripts, &subscriptcount));
/*
* Resolve the slot before the type switch. The reference notes that moving
* this below the switch corrupts the subscript list; here it is simply the
* clearer order, and the returned pointer is what an assignment expression
* evaluates to.
*/
PASS(errctx, akbasic_variable_get_subscript(variable, subscripts, subscriptcount, &slot));
switch ( lval->leaftype ) {
case AKBASIC_LEAF_IDENTIFIER_INT:
if ( rval->valuetype == AKBASIC_TYPE_INTEGER ) {
PASS(errctx, akbasic_variable_set_integer(variable, rval->intval, subscripts, subscriptcount));
} else if ( rval->valuetype == AKBASIC_TYPE_FLOAT ) {
PASS(errctx, akbasic_variable_set_integer(variable, (int64_t)rval->floatval, subscripts, subscriptcount));
} else {
FAIL_RETURN(errctx, AKBASIC_ERR_TYPE, "Incompatible types in variable assignment");
}
break;
case AKBASIC_LEAF_IDENTIFIER_FLOAT:
if ( rval->valuetype == AKBASIC_TYPE_INTEGER ) {
PASS(errctx, akbasic_variable_set_float(variable, (double)rval->intval, subscripts, subscriptcount));
} else if ( rval->valuetype == AKBASIC_TYPE_FLOAT ) {
PASS(errctx, akbasic_variable_set_float(variable, rval->floatval, subscripts, subscriptcount));
} else {
FAIL_RETURN(errctx, AKBASIC_ERR_TYPE, "Incompatible types in variable assignment");
}
break;
case AKBASIC_LEAF_IDENTIFIER_STRING:
FAIL_NONZERO_RETURN(errctx, (rval->valuetype != AKBASIC_TYPE_STRING), AKBASIC_ERR_TYPE,
"Incompatible types in variable assignment");
PASS(errctx, akbasic_variable_set_string(variable, rval->stringval, subscripts, subscriptcount));
break;
default:
FAIL_RETURN(errctx, AKBASIC_ERR_TYPE, "Invalid assignment");
}
variable->valuetype = rval->valuetype;
*dest = slot;
SUCCEED_RETURN(errctx);
}