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[qfcc] Delay conversion of nil in assignments

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It's not possible to take the address of constants (at this stage) and
trying to use a move instruction with .zero as source would result in
the VM complaining about null pointer access when bounds checking is on.
Thus, don't convert a nil source expression until it is known to be
safe, and use memset when it is not.
This commit is contained in:
Bill Currie 2020-03-11 22:57:48 +09:00
parent be5f11f33a
commit 5d349efe78
3 changed files with 33 additions and 11 deletions
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1
tools/qfcc/include/expr.h
View file

@ -595,6 +595,7 @@ int is_logic (int op) __attribute__((const));
int has_function_call (expr_t *e) __attribute__((pure));
int is_nil (expr_t *e) __attribute__((pure));
int is_string_val (expr_t *e) __attribute__((pure));
int is_float_val (expr_t *e) __attribute__((pure));
int is_vector_val (expr_t *e) __attribute__((pure));

6
tools/qfcc/source/expr.c
View file

@ -882,6 +882,12 @@ constant_expr (expr_t *e)
return new;
}
int
is_nil (expr_t *e)
{
return e->type == ex_nil;
}
int
is_string_val (expr_t *e)
{

23
tools/qfcc/source/expr_assign.c
View file

@ -345,22 +345,23 @@ assign_expr (expr_t *dst, expr_t *src)
}
src_type = get_type (src);
}
if (!is_void (dst_type) && src->type == ex_nil) {
if (!is_struct (dst_type) && is_nil (src)) {
// nil is a type-agnostic 0
// FIXME: assignment to compound types? error or memset?
src_type = dst_type;
convert_nil (src, src_type);
}
if (!is_nil (src)) {
if ((expr = check_types_compatible (dst, src))) {
// expr might be a valid expression, but if so, check_types_compatible
// will take care of everything
// expr might be a valid expression, but if so,
// check_types_compatible will take care of everything
return expr;
}
if ((expr = assign_vector_expr (dst, src))) {
return expr;
}
}
if (is_indirect (dst) && is_indirect (src)) {
debug (dst, "here");
@ -381,9 +382,19 @@ assign_expr (expr_t *dst, expr_t *src)
debug (dst, "here");
if (is_struct (dst_type)) {
dst = address_expr (dst, 0, 0);
if (is_nil (src)) {
int size = type_size (dst_type);
return new_memset_expr (dst, new_integer_expr (0),
new_integer_expr (size));
} else {
src = address_expr (src, 0, 0);
return new_move_expr (dst, src, dst_type, 1);
}
}
if (is_nil (src)) {
src_type = dst_type;
convert_nil (src, src_type);
}
if (dst->type == ex_expr) {
if (get_type (dst->e.expr.e1) == &type_entity) {
dst_type = dst->e.expr.type;
@ -420,6 +431,10 @@ assign_expr (expr_t *dst, expr_t *src)
}
}
if (is_nil (src)) {
src_type = dst_type;
convert_nil (src, src_type);
}
if (is_struct (dst_type)) {
return new_move_expr (dst, src, dst_type, 0);
}