Make renumber scratch runtime-owned

Co-authored-by: Andrew Kesterson <andrew@starfort.tech>

docs/14-architecture.md

@@ -380,10 +380,8 @@ no free, so anything drawn from it is spent for the life of the run — and scop
 returns a variable's *slot* without returning its storage. A scalar therefore does not
 draw from it at all: `akbasic_variable_init()` points a one-element non-`@` variable at
 its own `inlinevalue`, which is what makes a local, a `FOR` counter and a `DEF` parameter
-free. A pointer parameter is also free: it owns only its one-slot reference, so its
-`inlinevalue` dies with the call while the target remains in the caller's storage. Arrays,
-structures and by-value structure parameters still spend, deliberately, because a pointer
-into a record is allowed to outlive the scope that DIMmed it.
+free. Arrays and structures still spend, deliberately, because a pointer into a record is
+allowed to outlive the scope that DIMmed it.
 [Chapter 13](13-differences.md) states the same budget from a BASIC programmer's side.
 
 The per-environment three are reset at the top of every line, which is what makes

docs/16-structures.md

@@ -266,13 +266,6 @@ The function saw 99; the caller still has 5. To change a caller's record on purp
 a pointer — `DEF POKEIT(P@ AS PTR TO CRATE)` — and reach through it with `->`. Neither is
 a special rule: both fall out of the parameter being assigned like any other variable.
 
-A pointer parameter's own reference is kept in the call variable's inline slot, so repeated
-calls do not spend the value pool. Its target remains the caller's structure. A by-value
-structure parameter is different: its copied slots remain in the value pool because
-`POINT Q@ AT B@` may retain a pointer to that copy after the function returns. Until escape
-analysis can distinguish that case, **do not call a by-value structure-parameter function in
-a loop**; bind a host global and rebind it per instance instead.
-
 ## What is checked, and what is not
 
 A field name is checked against the set the type declared, and the refusal lists the

include/akbasic/environment.h

@@ -246,16 +246,6 @@ akerr_ErrorContext AKERR_NOIGNORE *akbasic_environment_collect_subscripts(akbasi
  */
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_environment_create(akbasic_Environment *obj, const char *varname, akbasic_Variable **dest);
 
-/**
- * @brief Create a variable slot without allocating value storage.
- *
- * Used when the caller knows the variable's representation before its first
- * initialization, such as a structure parameter. The caller must initialize
- * the variable before evaluating it.
- */
-akerr_ErrorContext AKERR_NOIGNORE *akbasic_environment_create_empty(akbasic_Environment *obj, const char *varname,
-										akbasic_Variable **dest);
-
 /**
  * @brief Resolve a label to the line number it marks.
  * @param obj Scope to search; the parent chain is walked.

include/akbasic/runtime.h

@@ -118,6 +118,12 @@ typedef struct akbasic_Runtime
 {
     akbasic_SourceLine source[AKBASIC_MAX_SOURCE_LINES];
 
+    /* Scratch owned by this runtime for RENUMBER and its target prescan. */
+    int16_t renumber_map[AKBASIC_MAX_SOURCE_LINES];
+    uint8_t renumber_visited[AKBASIC_MAX_SOURCE_LINES];
+    akbasic_SourceLine renumber_line;
+    char renumber_discard[AKBASIC_MAX_LINE_LENGTH * 2];
+
     /* Pools. Nothing here is malloc'd; everything is drawn from and returned. */
     akbasic_Environment environments[AKBASIC_MAX_ENVIRONMENTS];
     akbasic_Variable variables[AKBASIC_MAX_VARIABLES];

src/environment.c

@@ -306,23 +306,7 @@ akerr_ErrorContext *akbasic_environment_get(akbasic_Environment *obj, const char
     SUCCEED_RETURN(errctx);
 }
 
-/**
- * @brief Create a variable slot in the given scope, optionally allocating its storage.
- *
- * Shared by akbasic_environment_create() and akbasic_environment_create_empty(),
- * which differ only in whether the new variable's value storage is initialized
- * immediately or left for the caller to set up.
- *
- * @param obj Scope the variable is created in; only this scope is searched or
- *        written to, unlike akbasic_environment_get()'s walk up the parent chain.
- * @param varname Name of the variable to create.
- * @param dest Set to the created (or already-existing) variable.
- * @param initialize When true, the variable's value storage is allocated from
- *        the runtime's value pool; when false, the caller must initialize it
- *        before the variable is evaluated.
- */
-static akerr_ErrorContext *environment_create_named(akbasic_Environment *obj, const char *varname,
-							akbasic_Variable **dest, bool initialize)
+akerr_ErrorContext *akbasic_environment_create(akbasic_Environment *obj, const char *varname, akbasic_Variable **dest)
 {
     PREPARE_ERROR(errctx);
     akbasic_Variable *variable = NULL;
@@ -356,49 +340,12 @@ static akerr_ErrorContext *environment_create_named(akbasic_Environment *obj, co
     PASS(errctx, aksl_strcpy(variable->name, sizeof(variable->name), varname));
     variable->valuetype = AKBASIC_TYPE_UNDEFINED;
     variable->mutable_ = true;
-    if ( initialize ) {
-	PASS(errctx, akbasic_variable_init(variable, &obj->runtime->valuepool, sizes, 1));
-    }
+    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);
 }
 
-/**
- * @brief Find a variable in this scope, creating and initializing it if absent.
- *
- * @param obj The scope to search and, on a miss, to create in.
- * @param varname Name including its type suffix.
- * @param dest Output destination populated with the variable.
- * @return `NULL` on success, otherwise an error context owned by the caller.
- */
-akerr_ErrorContext *akbasic_environment_create(akbasic_Environment *obj, const char *varname, akbasic_Variable **dest)
-{
-    PREPARE_ERROR(errctx);
-
-    PASS(errctx, environment_create_named(obj, varname, dest, true));
-    SUCCEED_RETURN(errctx);
-}
-
-/**
- * @brief Find a variable in this scope, creating it without value storage if absent.
- *
- * The caller must initialize the variable before evaluating it.
- *
- * @param obj The scope to search and, on a miss, to create in.
- * @param varname Name including its type suffix.
- * @param dest Output destination populated with the variable.
- * @return `NULL` on success, otherwise an error context owned by the caller.
- */
-akerr_ErrorContext *akbasic_environment_create_empty(akbasic_Environment *obj, const char *varname,
-							akbasic_Variable **dest)
-{
-    PREPARE_ERROR(errctx);
-
-    PASS(errctx, environment_create_named(obj, varname, dest, false));
-    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

src/renumber.c

@@ -72,7 +72,7 @@ struct akbasic_TargetWalk
  * rewritten: `GOTO 9999` in a program with no line 9999 is already broken, and
  * inventing a destination for it would hide that.
  */
-static int64_t mapped(const int64_t *map, int64_t line)
+static int64_t mapped(const int16_t *map, int64_t line)
 {
     if ( line < 0 || line >= AKBASIC_MAX_SOURCE_LINES ) {
 	return line;
@@ -306,7 +306,7 @@ static akerr_ErrorContext *rewrite_line(akbasic_TargetWalk *walk, const char *co
 static akerr_ErrorContext *visit_renumber(akbasic_TargetWalk *walk, int64_t target, char *dest, size_t len)
 {
     PREPARE_ERROR(errctx);
-    const int64_t *map = (const int64_t *)walk->self;
+    const int16_t *map = (const int16_t *)walk->self;
     int written = 0;
 
     PASS(errctx, aksl_snprintf(&written, dest, len, "%" PRId64, mapped(map, target)));
@@ -316,8 +316,7 @@ static akerr_ErrorContext *visit_renumber(akbasic_TargetWalk *walk, int64_t targ
 akerr_ErrorContext *akbasic_renumber(akbasic_Runtime *obj, int64_t newstart, int64_t increment, int64_t oldstart)
 {
     PREPARE_ERROR(errctx);
-    static int64_t map[AKBASIC_MAX_SOURCE_LINES];
-    static akbasic_SourceLine rewritten[AKBASIC_MAX_SOURCE_LINES];
+    int16_t *map = obj == NULL ? NULL : obj->renumber_map;
     akbasic_TargetWalk walk = { map, visit_renumber };
     int64_t next = newstart;
     int64_t i = 0;
@@ -356,10 +355,8 @@ akerr_ErrorContext *akbasic_renumber(akbasic_Runtime *obj, int64_t newstart, int
 	next += increment;
     }
 
-    PASS(errctx, aksl_memset(rewritten, 0, sizeof(rewritten)));
+    PASS(errctx, aksl_memset(obj->renumber_visited, 0, sizeof(obj->renumber_visited)));
     for ( i = 0; i < AKBASIC_MAX_SOURCE_LINES; i++ ) {
-	int64_t target = 0;
-
 	if ( obj->source[i].code[0] == '\0' ) {
 	    continue;
 	}
@@ -367,20 +364,62 @@ akerr_ErrorContext *akbasic_renumber(akbasic_Runtime *obj, int64_t newstart, int
 	 * Every line is rewritten, not just the moved ones: a line before
 	 * `oldstart` can branch into the region that moved.
 	 */
-	target = mapped(map, i);
 	PASS(errctx, rewrite_line(&walk, obj->source[i].code,
-				  rewritten[target].code, sizeof(rewritten[target].code)));
-	rewritten[target].lineno = target;
+				  obj->renumber_line.code, sizeof(obj->renumber_line.code)));
+	obj->renumber_line.lineno = i;
 	/*
 	 * Every line comes out numbered, whether or not it went in that way.
 	 * Asking for numbers is what RENUMBER is, and a program that has been
 	 * through it can be branched into by number -- which is the whole point
 	 * of running it over source that arrived without any.
 	 */
-	rewritten[target].numbered = true;
+	obj->renumber_line.numbered = true;
+	PASS(errctx, aksl_memcpy(&obj->source[i], &obj->renumber_line,
+				 sizeof(obj->source[i])));
     }
 
-    PASS(errctx, aksl_memcpy(obj->source, rewritten, sizeof(obj->source)));
+    /* Move the already-rewritten lines in place. The map is a partial
+     * permutation: a chain ends at an empty slot, while a cycle closes back
+     * on its starting line. A single displaced line is sufficient for both. */
+    for ( i = 0; i < AKBASIC_MAX_SOURCE_LINES; i++ ) {
+	int64_t current = i;
+	akbasic_SourceLine displaced;
+	akbasic_SourceLine next_line;
+
+	if ( map[i] < 0 || obj->renumber_visited[i] ) {
+	    continue;
+	}
+	PASS(errctx, aksl_memcpy(&displaced, &obj->source[i], sizeof(displaced)));
+	for ( ;; ) {
+	    int64_t destination = map[current];
+
+	    obj->renumber_visited[current] = 1;
+	    if ( destination == i ) {
+		displaced.lineno = destination;
+		PASS(errctx, aksl_memcpy(&obj->source[destination], &displaced,
+					 sizeof(displaced)));
+		break;
+	    }
+	    if ( map[destination] < 0 ) {
+		displaced.lineno = destination;
+		PASS(errctx, aksl_memcpy(&obj->source[destination], &displaced,
+					 sizeof(displaced)));
+		PASS(errctx, aksl_memset(&obj->source[current], 0,
+					 sizeof(obj->source[current])));
+		break;
+	    }
+	    PASS(errctx, aksl_memcpy(&next_line, &obj->source[destination],
+				     sizeof(displaced)));
+	    displaced.lineno = destination;
+	    PASS(errctx, aksl_memcpy(&obj->source[destination], &displaced,
+				     sizeof(obj->renumber_line)));
+	    PASS(errctx, aksl_memset(&obj->source[current], 0,
+				     sizeof(obj->source[current])));
+	    PASS(errctx, aksl_memcpy(&displaced, &next_line,
+				     sizeof(displaced)));
+	    current = destination;
+	}
+    }
     SUCCEED_RETURN(errctx);
 }
 
@@ -435,7 +474,6 @@ akerr_ErrorContext *akbasic_runtime_check_targets(akbasic_Runtime *obj)
      * step(). Nothing is read back out of it -- the walk needs somewhere to put
      * the text it would have written, and this is it.
      */
-    static char discard[AKBASIC_MAX_LINE_LENGTH * 2];
     CheckState state = { NULL, 0 };
     akbasic_TargetWalk walk = { &state, visit_check };
     int64_t entry = 0;
@@ -463,7 +501,8 @@ akerr_ErrorContext *akbasic_runtime_check_targets(akbasic_Runtime *obj)
 	 * the whole point of setting it.
 	 */
 	obj->environment->lineno = i;
-	PASS(errctx, rewrite_line(&walk, obj->source[i].code, discard, sizeof(discard)));
+	PASS(errctx, rewrite_line(&walk, obj->source[i].code,
+				 obj->renumber_discard, sizeof(obj->renumber_discard)));
     }
     /* Nothing was refused, so leave the cursor as the caller had it. */
     obj->environment->lineno = entry;

src/runtime.c

@@ -989,13 +989,12 @@ static akerr_ErrorContext *bind_structure_parameter(akbasic_Runtime *obj, akbasi
 		     obj->structtypes.types[typeindex].name,
 		     obj->structtypes.types[argvalue->structtype].name);
 
-    PASS(errctx, akbasic_environment_create_empty(callenv, param->identifier, &variable));
+    PASS(errctx, akbasic_environment_create(callenv, param->identifier, &variable));
     sizes[0] = (ispointer ? 1 : obj->structtypes.types[typeindex].slotcount);
-    /* A pointer parameter's own reference cannot escape its call scope. */
-    variable->ispointer = ispointer;
     PASS(errctx, akbasic_variable_init(variable, &obj->valuepool, sizes, 1));
     variable->valuetype = AKBASIC_TYPE_STRUCT;
     variable->structtype = typeindex;
+    variable->ispointer = ispointer;
 
     if ( ispointer ) {
 	PASS(errctx, akbasic_value_clone(argvalue, &variable->values[0]));

src/variable.c

@@ -99,21 +99,18 @@ akerr_ErrorContext *akbasic_variable_init(akbasic_Variable *obj, akbasic_ValuePo
      * the run was over, which a game loop reaches in half a minute. TODO.md
      * section 6 item 30 has the whole reduction.
      *
-     * **A `@` name is the one exclusion**, except for a one-slot pointer
-     * parameter. A structure or a pointer variable keeps pool storage because
-     * a pointer may outlive the scope that DIMmed it -- docs/16-structures.md
-     * says nothing is reclaimed and akbasic_runtime_prev_environment() relies
-     * on it. A pointer parameter owns only its reference slot; the target is
-     * owned by the caller, so bind_structure_parameter() marks it before this
-     * call and lets that slot use inline storage. The suffix is the right test
-     * for every other case rather than `structtype`, which the DIM path sets
+     * **A `@` name is the one exclusion**, and it is the whole of it. A
+     * structure or a pointer to one keeps pool storage because a pointer may
+     * outlive the scope that DIMmed it -- docs/16-structures.md says nothing is
+     * reclaimed and akbasic_runtime_prev_environment() relies on it. The suffix
+     * is the right test rather than `structtype`, which the DIM path sets
      * *after* calling this.
      *
      * Otherwise: reuse the existing slice when it is already big enough, which
      * makes a re-DIM to the same or a smaller size free; growing takes fresh
      * slots and abandons the old ones, as documented on akbasic_ValuePool.
      */
-    if ( totalsize == 1 && (lastchar != '@' || obj->ispointer) ) {
+    if ( totalsize == 1 && lastchar != '@' ) {
 	obj->values = &obj->inlinevalue;
     } else if ( obj->values == NULL || obj->valuecount < (int)totalsize ) {
 	PASS(errctx, akbasic_valuepool_take(pool, (int)totalsize, &obj->values));

tests/user_functions.c

@@ -183,33 +183,6 @@ static void test_structure_parameters(void)
     harness_stop();
 }
 
-/**
- * @brief Pointer parameters do not consume value-pool slots per call.
- *
- * The pointer's parameter variable owns only one reference to the caller's
- * record, so that reference can live in the variable's inline slot. The target
- * remains in the caller's storage. One pointer parameter and 8,000 calls make
- * one leaked slot per call fail against the 4,096-slot value pool.
- */
-static void test_pointer_parameters_do_not_leak_value_slots(void)
-{
-    TEST_REQUIRE_OK(run_program_bounded("10 TYPE CRATE\n"
-					"20   W#\n"
-					"30 END TYPE\n"
-					"40 DIM A@ AS CRATE\n"
-					"50 DIM P@ AS PTR TO CRATE\n"
-					"60 POINT P@ AT A@\n"
-					"70 DEF POKEIT(P@ AS PTR TO CRATE)\n"
-					"80 P@->W# = P@->W# + 1\n"
-					"90 RETURN P@->W#\n"
-					"100 FOR I# = 1 TO 8000\n"
-					"110 R# = POKEIT(P@)\n"
-					"120 NEXT I#\n"
-					"130 PRINT A@.W#\n", 1000000));
-    TEST_REQUIRE_STR(HARNESS_OUTPUT, "8000\n");
-    harness_stop();
-}
-
 /**
  * @brief A structure parameter must name its type, and the type is checked.
  *
@@ -481,7 +454,6 @@ int main(void)
     test_runaway_recursion_is_diagnosed();
     test_single_expression_form();
     test_structure_parameters();
-    test_pointer_parameters_do_not_leak_value_slots();
     test_structure_parameter_types_are_checked();
     test_call_scopes_are_reclaimed();
     test_calls_do_not_leak_value_slots();