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Fix dereference behavior on mixed subscript and arrow / dot operators #182

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merged 1 commit into from
Mar 24, 2025
+76 −18
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Fix dereference behavior on mixed subscript and arrow / dot operators #182

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4 changes: 1 addition & 3 deletions src/globals.c
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Original file line number Diff line number Diff line change
Expand Up @@ -250,9 +250,7 @@ void hashmap_free(hashmap_t *map)
next = cur->next;
free(cur->key);
free(cur->val);
/* FIXME: Remove this if-clause will cause double free error */
if (cur != map->buckets[0])
free(cur);
free(cur);
cur = next;
}
}
Expand Down
47 changes: 32 additions & 15 deletions src/parser.c
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Original file line number Diff line number Diff line change
Expand Up @@ -750,7 +750,7 @@ void read_lvalue(lvalue_t *lvalue,
var_t *var,
block_t *parent,
basic_block_t **bb,
int eval,
bool eval,
opcode_t op);

/* Maintain a stack of expression values and operators, depending on next
Expand Down Expand Up @@ -805,7 +805,7 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)

lex_peek(T_identifier, token);
var_t *var = find_var(token, parent);
read_lvalue(&lvalue, var, parent, bb, 0, OP_generic);
read_lvalue(&lvalue, var, parent, bb, false, OP_generic);

if (!lvalue.is_reference) {
ph1_ir = add_ph1_ir(OP_address_of);
Expand All @@ -825,7 +825,7 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)
int open_bracket = lex_accept(T_open_bracket);
lex_peek(T_identifier, token);
var_t *var = find_var(token, parent);
read_lvalue(&lvalue, var, parent, bb, 1, OP_generic);
read_lvalue(&lvalue, var, parent, bb, true, OP_generic);
if (open_bracket)
lex_expect(T_close_bracket);

Expand Down Expand Up @@ -962,7 +962,7 @@ void read_expr_operand(block_t *parent, basic_block_t **bb)
} else if (var) {
/* evalue lvalue expression */
lvalue_t lvalue;
read_lvalue(&lvalue, var, parent, bb, 1, prefix_op);
read_lvalue(&lvalue, var, parent, bb, true, prefix_op);

/* is it an indirect call with function pointer? */
if (lex_peek(T_open_bracket, NULL)) {
Expand Down Expand Up @@ -1234,13 +1234,13 @@ void read_lvalue(lvalue_t *lvalue,
var_t *var,
block_t *parent,
basic_block_t **bb,
int eval,
bool eval,
opcode_t prefix_op)
{
ph1_ir_t *ph1_ir;
var_t *vd;
int is_address_got = 0;
int is_member = 0;
bool is_address_got = false;
bool is_member = false;

/* already peeked and have the variable */
lex_expect(T_identifier);
Expand All @@ -1260,6 +1260,23 @@ void read_lvalue(lvalue_t *lvalue,
while (lex_peek(T_open_square, NULL) || lex_peek(T_arrow, NULL) ||
lex_peek(T_dot, NULL)) {
if (lex_accept(T_open_square)) {
/* if subscripted member's is not yet resolved, dereference to
* resolve base address.
* e.g., dereference of "->" in "data->raw[0]" would be performed
* here.
*/
if (lvalue->is_reference && lvalue->is_ptr && is_member) {
ph1_ir = add_ph1_ir(OP_read);
ph1_ir->src0 = opstack_pop();
vd = require_var(parent);
strcpy(vd->var_name, gen_name());
ph1_ir->dest = vd;
opstack_push(vd);
ph1_ir->size = 4;
add_insn(parent, *bb, OP_read, ph1_ir->dest, ph1_ir->src0, NULL,
ph1_ir->size, NULL);
}

/* var must be either a pointer or an array of some type */
if (var->is_ptr == 0 && var->array_size == 0)
error("Cannot apply square operator to non-pointer");
Expand Down Expand Up @@ -1303,8 +1320,8 @@ void read_lvalue(lvalue_t *lvalue,
ph1_ir->src1, 0, NULL);

lex_expect(T_close_square);
is_address_got = 1;
is_member = 1;
is_address_got = true;
is_member = true;
lvalue->is_reference = true;
} else {
char token[MAX_ID_LEN];
Expand All @@ -1313,7 +1330,7 @@ void read_lvalue(lvalue_t *lvalue,
/* resolve where the pointer points at from the calculated
* address in a structure.
*/
if (is_member == 1) {
if (is_member) {
ph1_ir = add_ph1_ir(OP_read);
ph1_ir->src0 = opstack_pop();
vd = require_var(parent);
Expand All @@ -1327,7 +1344,7 @@ void read_lvalue(lvalue_t *lvalue,
} else {
lex_expect(T_dot);

if (is_address_got == 0) {
if (!is_address_got) {
ph1_ir = add_ph1_ir(OP_address_of);
ph1_ir->src0 = opstack_pop();
vd = require_var(parent);
Expand All @@ -1337,7 +1354,7 @@ void read_lvalue(lvalue_t *lvalue,
add_insn(parent, *bb, OP_address_of, ph1_ir->dest,
ph1_ir->src0, NULL, 0, NULL);

is_address_got = 1;
is_address_got = true;
}
}

Expand Down Expand Up @@ -1376,8 +1393,8 @@ void read_lvalue(lvalue_t *lvalue,
add_insn(parent, *bb, OP_add, ph1_ir->dest, ph1_ir->src0,
ph1_ir->src1, 0, NULL);

is_address_got = 1;
is_member = 1;
is_address_got = true;
is_member = true;
}
}

Expand Down Expand Up @@ -1860,7 +1877,7 @@ bool read_body_assignment(char *token,
int size = 0;

/* has memory address that we want to set */
read_lvalue(&lvalue, var, parent, bb, 0, OP_generic);
read_lvalue(&lvalue, var, parent, bb, false, OP_generic);
size = lvalue.size;

if (lex_accept(T_increment)) {
Expand Down
43 changes: 43 additions & 0 deletions tests/driver.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,49 @@ int main() {
}
EOF

# Mixed subscript and arrow / dot operators,
# excerpted and modified from issue #165
try_output 0 "DDDDDDMMMEEE1" << EOF
#include <stdlib.h>
#include <string.h>
char a[100];
typedef struct {
char *raw;
} data_t;
int main() {
strcpy(a, "DATA");
data_t *data = malloc(sizeof(data_t));
data->raw = a;
data_t data2;
data2.raw = a;
char *raw = data->raw;
char *raw2 = data2.raw;
/* mixed arrow / dot with subscript operators dereference */
printf("%c", a[0]);
printf("%c", raw[0]);
printf("%c", data->raw[0]);
printf("%c", a[0]);
printf("%c", raw2[0]);
printf("%c", data2.raw[0]);
/* mixed arrow / dot with subscript operators assignment */
data2.raw[0] = 'M';
data->raw[1] = 'E';
printf("%c", a[0]);
printf("%c", raw[0]);
printf("%c", data->raw[0]);
printf("%c", a[1]);
printf("%c", raw2[1]);
printf("%c", data2.raw[1]);
/* their addresses should be same */
printf("%d", &data2.raw[0] == &data->raw[0]);
free(data);
return 0;
}
EOF

# global initialization
try_ 20 << EOF
int a = 5 * 2;
Expand Down