Module Name: src
Committed By: rillig
Date: Thu Mar 25 13:10:19 UTC 2021
Modified Files:
src/usr.bin/xlint/lint1: init.c
Log Message:
lint: add comments about things left to do, from code review
No functional change.
To generate a diff of this commit:
cvs rdiff -u -r1.118 -r1.119 src/usr.bin/xlint/lint1/init.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/xlint/lint1/init.c
diff -u src/usr.bin/xlint/lint1/init.c:1.118 src/usr.bin/xlint/lint1/init.c:1.119
--- src/usr.bin/xlint/lint1/init.c:1.118 Thu Mar 25 01:42:53 2021
+++ src/usr.bin/xlint/lint1/init.c Thu Mar 25 13:10:19 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: init.c,v 1.118 2021/03/25 01:42:53 rillig Exp $ */
+/* $NetBSD: init.c,v 1.119 2021/03/25 13:10:19 rillig Exp $ */
/*
* Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
#include <sys/cdefs.h>
#if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: init.c,v 1.118 2021/03/25 01:42:53 rillig Exp $");
+__RCSID("$NetBSD: init.c,v 1.119 2021/03/25 13:10:19 rillig Exp $");
#endif
#include <stdlib.h>
@@ -59,21 +59,30 @@ __RCSID("$NetBSD: init.c,v 1.118 2021/03
* int array_nested[2][2] = { { 11, 12 }, { 21, 22 } };
*
* struct { int x, y; } point = { 3, 4 };
- * struct { int x, y; } point = { .y = 3, .x = 4 };
+ * struct { int x, y; } point = { .y = 4, .x = 3 };
*
- * Any scalar expression in the initializer may be surrounded by an extra pair
- * of braces, like in the example 'number_with_braces' (C99 6.7.8p11). For
- * multi-dimensional arrays, the inner braces may be omitted like in
+ * Any scalar expression in the initializer may be surrounded by arbitrarily
+ * many extra pairs of braces, like in the example 'number_with_braces' (C99
+ * 6.7.8p11).
+ *
+ * For multi-dimensional arrays, the inner braces may be omitted like in
* array_flat or spelled out like in array_nested.
*
* For the initializer, the grammar parser calls these functions:
*
- * init_lbrace for each '{'
- * init_using_expr for each value
- * init_rbrace for each '}'
+ * begin_initialization
+ * init_lbrace for each '{'
+ * designator_push_name for each '.member' before '='
+ * designator_push_subscript for each '[123]' before '='
+ * init_using_expr for each expression
+ * init_rbrace for each '}'
+ * end_initialization
*
* The state of the current initialization is stored in initstk, a stack of
* initstack_element, one element per type aggregate level.
+ * XXX: Or is that "one element per brace level"? C99 mandates in 6.7.8p17
+ * that "each brace-enclosed initializer list has an associated current
+ * object".
*
* Most of the time, the topmost level of initstk contains a scalar type, and
* its remaining count toggles between 1 and 0.
@@ -87,16 +96,11 @@ __RCSID("$NetBSD: init.c,v 1.118 2021/03
/*
* Type of stack which is used for initialization of aggregate types.
*
- * XXX: Since C99, a stack is an inappropriate data structure for modelling
- * an initialization, since the designators don't have to be listed in a
- * particular order and can designate parts of sub-objects. The member names
+ * XXX: Since C99, the initializers can be listed in arbitrary order by using
+ * designators to specify the sub-object to be initialized. The member names
* of non-leaf structs may thus appear repeatedly, as demonstrated in
* d_init_pop_member.c.
*
- * XXX: During initialization, there may be members of the top-level struct
- * that are partially initialized. The simple i_remaining cannot model this
- * appropriately.
- *
* See C99 6.7.8, which spans 6 pages full of tricky details and carefully
* selected examples.
*/
@@ -107,8 +111,11 @@ typedef struct initstack_element {
*
* On the outermost element, this is always NULL since the outermost
* initializer-expression may be enclosed in an optional pair of
- * braces. This optional pair of braces is handled by the combination
- * of i_type and i_subt.
+ * braces, as of the current implementation.
+ *
+ * FIXME: This approach is wrong. It's not that the outermost
+ * initializer may be enclosed in additional braces, it's every scalar
+ * that may be enclosed in additional braces, as of C99 6.7.8p11.
*
* Everywhere else it is nonnull.
*/
@@ -131,28 +138,48 @@ typedef struct initstack_element {
*
* During initialization, only the top 2 elements of the stack are
* looked at.
+ *
+ * XXX: Having i_subt here is the wrong approach, it should not be
+ * necessary at all; see i_type.
*/
type_t *i_subt;
/*
- * This level of the initializer requires a '}' to be completed.
+ * Whether this level of the initializer requires a '}' to be
+ * completed.
*
* Multidimensional arrays do not need a closing brace to complete
* an inner array; for example, { 1, 2, 3, 4 } is a valid initializer
- * for int arr[2][2].
+ * for 'int arr[2][2]'.
*
* TODO: Do structs containing structs need a closing brace?
* TODO: Do arrays of structs need a closing brace after each struct?
+ *
+ * XXX: Double-check whether this is the correct approach at all; see
+ * i_type.
*/
bool i_brace: 1;
/* Whether i_type is an array of unknown size. */
bool i_array_of_unknown_size: 1;
+
+ /*
+ * XXX: This feels wrong. Whether or not there has been a named
+ * initializer (called 'designation' since C99) should not matter at
+ * all. Even after an initializer with designation, counting of the
+ * remaining elements continues, see C99 6.7.8p17.
+ */
bool i_seen_named_member: 1;
/*
* For structs, the next member to be initialized by an initializer
* without an optional designator.
+ *
+ * FIXME: The name is wrong. C99 defines the "current object" as
+ * being the subobject being initialized, while this is rather the
+ * next member. This only makes sense for structs anyway and should
+ * be amended by i_next_subscript for arrays. See C99 6.7.8p17 and
+ * footnote 128 for unions.
*/
sym_t *i_current_object;
@@ -170,14 +197,23 @@ typedef struct initstack_element {
* XXX: for structs?
* XXX: for unions?
* XXX: for arrays?
+ *
+ * XXX: Having the count of remaining objects should not be necessary.
+ * It is probably clearer to use i_next_member and i_next_subscript
+ * (as suggested in i_current_object) for this purpose.
*/
int i_remaining;
/*
* The initialization state of the enclosing data structure
* (struct, union, array).
+ *
+ * XXX: Or for a scalar, for the top-level element, or for expressions
+ * in redundant braces such as '{{{{ 0 }}}}' (not yet implemented as
+ * of 2021-03-25).
*/
struct initstack_element *i_enclosing;
+
} initstack_element;
/*
@@ -223,8 +259,12 @@ struct initialization {
static struct initialization *init;
+/* XXX: unnecessary prototype since it is not recursive */
static bool init_array_using_string(tnode_t *);
+
+/* TODO: replace the following functions with current_init */
+
bool *
current_initerr(void)
{
@@ -253,10 +293,10 @@ current_initstk(void)
return &init->initstk;
}
-#define initerr (*current_initerr())
-#define initsym (*current_initsym())
-#define initstk (*current_initstk())
-#define namedmem (*current_namedmem())
+#define initerr (*current_initerr())
+#define initsym (*current_initsym())
+#define initstk (*current_initstk())
+#define namedmem (*current_namedmem())
#ifndef DEBUG
@@ -330,9 +370,18 @@ debug_named_member(void)
debug_printf("\n");
}
+/*
+ * TODO: try whether a single-line output is more readable
+ *
+ * TODO: only log the top of the stack after each modifying operation
+ *
+ * TODO: wrap all write accesses to initstack_element in setter functions
+ */
static void
debug_initstack_element(const initstack_element *elem)
{
+ /* TODO: use debug_ind++ instead of the leading spaces here */
+
if (elem->i_type != NULL)
debug_step(" i_type = %s", type_name(elem->i_type));
if (elem->i_subt != NULL)
@@ -354,6 +403,9 @@ debug_initstack_element(const initstack_
debug_step(" i_remaining = %d", elem->i_remaining);
}
+/*
+ * TODO: only call debug_initstack after each push/pop.
+ */
static void
debug_initstack(void)
{
@@ -410,7 +462,7 @@ designator_push_name(sbuf_t *sb)
/*
* XXX: Why is this a circular list?
* XXX: Why is this a doubly-linked list?
- * A simple stack should suffice.
+ * A simple queue should suffice.
*/
nam->n_prev = nam->n_next = nam;
namedmem = nam;
@@ -425,11 +477,21 @@ designator_push_name(sbuf_t *sb)
}
/*
- * A struct member that has array type is initialized using a designator.
+ * A sub-object of an array is initialized using a designator. This does not
+ * have to be an array element directly, it can also be used to initialize
+ * only a sub-object of the array element.
*
* C99 example: struct { int member[4]; } var = { [2] = 12345 };
*
* GNU example: struct { int member[4]; } var = { [1 ... 3] = 12345 };
+ *
+ * TODO: test the following initialization with an outer and an inner type:
+ *
+ * .deeply[0].nested = {
+ * .deeply[1].nested = {
+ * 12345,
+ * },
+ * }
*/
void
designator_push_subscript(range_t range)
@@ -440,6 +502,7 @@ designator_push_subscript(range_t range)
debug_leave();
}
+/* TODO: add support for array subscripts, not only named members */
static void
designator_shift_name(void)
{
@@ -460,6 +523,8 @@ designator_shift_name(void)
/*
* Initialize the initialization stack by putting an entry for the object
* which is to be initialized on it.
+ *
+ * TODO: merge into begin_initialization
*/
void
initstack_init(void)
@@ -469,11 +534,14 @@ initstack_init(void)
if (initerr)
return;
+ /* TODO: merge into end_initialization */
/* free memory used in last initialization */
while ((istk = initstk) != NULL) {
initstk = istk->i_enclosing;
free(istk);
}
+
+ /* TODO: merge into init_using_expr */
while (namedmem != NULL)
designator_shift_name();
@@ -485,6 +553,7 @@ initstack_init(void)
*/
if (initsym->s_type->t_tspec == ARRAY && is_incomplete(initsym->s_type))
initsym->s_type = duptyp(initsym->s_type);
+ /* TODO: does 'duptyp' create a memory leak? */
istk = initstk = xcalloc(1, sizeof (initstack_element));
istk->i_subt = initsym->s_type;
@@ -494,12 +563,17 @@ initstack_init(void)
debug_leave();
}
+/* TODO: document me */
static void
initstack_pop_item_named_member(void)
{
initstack_element *istk = initstk;
sym_t *m;
+ /*
+ * TODO: fix wording of the debug message; this doesn't seem to be
+ * related to initializing the named member.
+ */
debug_step("initializing named member '%s'", namedmem->n_name);
if (istk->i_type->t_tspec != STRUCT &&
@@ -534,6 +608,7 @@ initstack_pop_item_named_member(void)
istk->i_seen_named_member = true;
}
+/* TODO: think of a better name than 'pop' */
static void
initstack_pop_item_unnamed(void)
{
@@ -558,6 +633,7 @@ initstack_pop_item_unnamed(void)
}
}
+/* TODO: think of a better name than 'pop' */
static void
initstack_pop_item(void)
{
@@ -600,6 +676,7 @@ initstack_pop_brace(void)
debug_initstack();
do {
brace = initstk->i_brace;
+ /* TODO: improve wording of the debug message */
debug_step("loop brace=%d", brace);
initstack_pop_item();
} while (!brace);
@@ -611,6 +688,7 @@ initstack_pop_brace(void)
* Take all entries which cannot be used for further initializers from the
* stack, but do this only if they do not require a closing brace.
*/
+/* TODO: think of a better name than 'pop' */
static void
initstack_pop_nobrace(void)
{
@@ -647,6 +725,8 @@ extend_if_array_of_unknown_size(void)
debug_step("extended type is '%s'", type_name(istk->i_type));
}
+/* TODO: document me */
+/* TODO: think of a better name than 'push' */
static void
initstack_push_array(void)
{
@@ -674,9 +754,15 @@ initstack_push_array(void)
type_name(istk->i_type), istk->i_remaining);
}
+/* TODO: document me */
+/* TODO: think of a better name than 'push' */
static bool
initstack_push_struct_or_union(void)
{
+ /*
+ * TODO: remove unnecessary 'const' for variables in functions that
+ * fit on a single screen. Keep it for larger functions.
+ */
initstack_element *const istk = initstk;
int cnt;
sym_t *m;
@@ -698,7 +784,16 @@ initstack_push_struct_or_union(void)
m != NULL; m = m->s_next) {
if (m->s_bitfield && m->s_name == unnamed)
continue;
+ /*
+ * TODO: split into separate functions:
+ *
+ * look_up_array_next
+ * look_up_array_designator
+ * look_up_struct_next
+ * look_up_struct_designator
+ */
if (namedmem != NULL) {
+ /* XXX: this log entry looks unnecessarily verbose */
debug_step("have member '%s', want member '%s'",
m->s_name, namedmem->n_name);
if (strcmp(m->s_name, namedmem->n_name) == 0) {
@@ -739,6 +834,8 @@ initstack_push_struct_or_union(void)
return false;
}
+/* TODO: document me */
+/* TODO: think of a better name than 'push' */
static void
initstack_push(void)
{
@@ -786,6 +883,7 @@ again:
if (namedmem != NULL) {
debug_step("pop scalar");
pop:
+ /* TODO: extract this into end_initializer_level */
inxt = initstk->i_enclosing;
free(istk);
initstk = inxt;
@@ -807,6 +905,9 @@ check_too_many_initializers(void)
const initstack_element *istk = initstk;
if (istk->i_remaining > 0)
return;
+ /*
+ * FIXME: even with named members, there can be too many initializers
+ */
if (istk->i_array_of_unknown_size || istk->i_seen_named_member)
return;
@@ -857,6 +958,7 @@ initstack_next_brace(void)
debug_leave();
}
+/* TODO: document me, or think of a better name */
static void
initstack_next_nobrace(tnode_t *tn)
{
@@ -892,6 +994,7 @@ initstack_next_nobrace(tnode_t *tn)
debug_leave();
}
+/* TODO: document me */
void
init_lbrace(void)
{
@@ -951,6 +1054,7 @@ check_bit_field_init(const tnode_t *ln,
static void
check_non_constant_initializer(const tnode_t *tn, scl_t sclass)
{
+ /* TODO: rename CON to CONSTANT to avoid ambiguity with CONVERT */
if (tn == NULL || tn->tn_op == CON)
return;
@@ -969,8 +1073,8 @@ check_non_constant_initializer(const tno
}
/*
- * Local initialization of non-array-types with only one expression without
- * braces is done by ASSIGN.
+ * Initialize a non-array object with automatic storage duration and only a
+ * single initializer expression without braces by delegating to ASSIGN.
*/
static bool
init_using_assign(tnode_t *rn)
@@ -983,11 +1087,14 @@ init_using_assign(tnode_t *rn)
return false;
debug_step("handing over to ASSIGN");
+
ln = new_name_node(initsym, 0);
ln->tn_type = tduptyp(ln->tn_type);
ln->tn_type->t_const = false;
+
tn = build(ASSIGN, ln, rn);
expr(tn, false, false, false, false);
+
/* XXX: why not clean up the initstack here already? */
return true;
}
@@ -1018,7 +1125,7 @@ check_init_expr(tnode_t *tn, scl_t sclas
return;
/*
- * Store the tree memory. This is necessary because otherwise
+ * Preserve the tree memory. This is necessary because otherwise
* expr() would free it.
*/
tmem = tsave();
@@ -1110,9 +1217,14 @@ init_array_using_string(tnode_t *tn)
return false;
}
/* XXX: duplicate code, see below */
+
/* Put the array at top of stack */
initstack_push();
istk = initstk;
+
+
+ /* TODO: what if both i_type and i_subt are ARRAY? */
+
} else if (istk->i_type != NULL && istk->i_type->t_tspec == ARRAY) {
debug_step("type array");
t = istk->i_type->t_subt->t_tspec;
@@ -1123,6 +1235,11 @@ init_array_using_string(tnode_t *tn)
return false;
}
/* XXX: duplicate code, see above */
+
+ /*
+ * TODO: is this really not needed in the branch above this
+ * one?
+ */
/*
* If the array is already partly initialized, we are
* wrong here.
@@ -1144,10 +1261,21 @@ init_array_using_string(tnode_t *tn)
istk->i_type->t_dim = len + 1;
setcomplete(istk->i_type, true);
} else {
+ /*
+ * TODO: check for buffer overflow in the object to be
+ * initialized
+ */
+ /* XXX: double-check for off-by-one error */
if (istk->i_type->t_dim < len) {
/* non-null byte ignored in string initializer */
warning(187);
}
+
+ /*
+ * TODO: C99 6.7.8p14 allows a string literal to be enclosed
+ * in optional redundant braces, just like scalars. Add tests
+ * for this.
+ */
}
/* In every case the array is initialized completely. */
