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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2020-08-12 22:26:28 +0200 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2020-08-17 00:38:46 +0200 |
| commit | 8b3cbf54ad42c68f5ea2fa5bc2cef5ce9e608571 (patch) | |
| tree | d415ba8c9847ce463b0f967878d663737f6e9084 /evaluate.c | |
| parent | 8b5d92da3b1919f574decb542d93fde82693fe71 (diff) | |
| download | sparse-dev-8b3cbf54ad42c68f5ea2fa5bc2cef5ce9e608571.tar.gz | |
union-cast: teach sparse about union casts
A cast to union type is a GCC extension similar to a compound
literal just for union, using the syntax of a cast.
However, sparse doesn't know about them and treats them like
other casts to non-scalars.
So, teach sparse about them, convert them to the corresponding
compound literal and add a warning flag to enable/disable the
associated warning: -W[no-]union-cast.
Note: a difference between union casts and compound literals
is that the union casts yield rvalues while compound
literals are lvalues but this distinction is not yet done
in this series.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Diffstat (limited to 'evaluate.c')
| -rw-r--r-- | evaluate.c | 47 |
1 files changed, 46 insertions, 1 deletions
@@ -2948,6 +2948,26 @@ static int cast_flags(struct expression *expr, struct expression *old) return flags; } +/// +// check if a type matches one of the members of a union type +// @utype: the union type +// @type: to type to check +// @return: to identifier of the matching type in the union. +static struct symbol *find_member_type(struct symbol *utype, struct symbol *type) +{ + struct symbol *t, *member; + + if (utype->type != SYM_UNION) + return NULL; + + FOR_EACH_PTR(utype->symbol_list, member) { + classify_type(member, &t); + if (type == t) + return member; + } END_FOR_EACH_PTR(member); + return NULL; +} + static struct symbol *evaluate_compound_literal(struct expression *expr, struct expression *source) { struct expression *addr = alloc_expression(expr->pos, EXPR_SYMBOL); @@ -2973,6 +2993,7 @@ static struct symbol *evaluate_cast(struct expression *expr) struct expression *source = expr->cast_expression; struct symbol *ctype; struct symbol *ttype, *stype; + struct symbol *member; int tclass, sclass; struct ident *tas = NULL, *sas = NULL; @@ -3022,8 +3043,32 @@ static struct symbol *evaluate_cast(struct expression *expr) if (expr->type == EXPR_FORCE_CAST) goto out; - if (tclass & (TYPE_COMPOUND | TYPE_FN)) + if (tclass & (TYPE_COMPOUND | TYPE_FN)) { + /* + * Special case: cast to union type (GCC extension) + * The effect is similar to a compound literal except + * that the result is a rvalue. + */ + if ((member = find_member_type(ttype, stype))) { + struct expression *item, *init; + + if (Wunion_cast) + warning(expr->pos, "cast to union type"); + + item = alloc_expression(source->pos, EXPR_IDENTIFIER); + item->expr_ident = member->ident; + item->ident_expression = source; + + init = alloc_expression(source->pos, EXPR_INITIALIZER); + add_expression(&init->expr_list, item); + + // FIXME: this should be a rvalue + evaluate_compound_literal(expr, init); + return ctype; + } + warning(expr->pos, "cast to non-scalar"); + } if (sclass & TYPE_COMPOUND) warning(expr->pos, "cast from non-scalar"); |