[PATCH] implement __builtin_offsetof()

From: Al Viro
Date: Tue Jun 26 2007 - 16:06:32 EST

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Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
evaluate.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
expand.c | 1 +
expression.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++
expression.h | 10 +++++++
ident-list.h | 1 +
inline.c | 18 +++++++++++-
lib.c | 1 -
show-parse.c | 1 +
8 files changed, 181 insertions(+), 2 deletions(-)

diff --git a/evaluate.c b/evaluate.c
index 07ebf0c..c702ac4 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -2608,6 +2608,87 @@ static struct symbol *evaluate_call(struct expression *expr)
return expr->ctype;
}

+static struct symbol *evaluate_offsetof(struct expression *expr)
+{
+ struct expression *e = expr->down;
+ struct symbol *ctype = expr->in;
+ int class;
+
+ if (expr->op == '.') {
+ struct symbol *field;
+ int offset = 0;
+ if (!ctype) {
+ expression_error(expr, "expected structure or union");
+ return NULL;
+ }
+ examine_symbol_type(ctype);
+ class = classify_type(ctype, &ctype);
+ if (class != TYPE_COMPOUND) {
+ expression_error(expr, "expected structure or union");
+ return NULL;
+ }
+
+ field = find_identifier(expr->ident, ctype->symbol_list, &offset);
+ if (!field) {
+ expression_error(expr, "unknown member");
+ return NULL;
+ }
+ ctype = field;
+ expr->type = EXPR_VALUE;
+ expr->value = offset;
+ expr->ctype = size_t_ctype;
+ } else {
+ if (!ctype) {
+ expression_error(expr, "expected structure or union");
+ return NULL;
+ }
+ examine_symbol_type(ctype);
+ class = classify_type(ctype, &ctype);
+ if (class != (TYPE_COMPOUND | TYPE_PTR)) {
+ expression_error(expr, "expected array");
+ return NULL;
+ }
+ ctype = ctype->ctype.base_type;
+ if (!expr->index) {
+ expr->type = EXPR_VALUE;
+ expr->value = 0;
+ expr->ctype = size_t_ctype;
+ } else {
+ struct expression *idx = expr->index, *m;
+ struct symbol *i_type = evaluate_expression(idx);
+ int i_class = classify_type(i_type, &i_type);
+ if (!is_int(i_class)) {
+ expression_error(expr, "non-integer index");
+ return NULL;
+ }
+ unrestrict(idx, i_class, &i_type);
+ idx = cast_to(idx, size_t_ctype);
+ m = alloc_const_expression(expr->pos,
+ ctype->bit_size >> 3);
+ m->ctype = size_t_ctype;
+ expr->type = EXPR_BINOP;
+ expr->left = idx;
+ expr->right = m;
+ expr->op = '*';
+ expr->ctype = size_t_ctype;
+ }
+ }
+ if (e) {
+ struct expression *copy = __alloc_expression(0);
+ *copy = *expr;
+ if (e->type == EXPR_OFFSETOF)
+ e->in = ctype;
+ if (!evaluate_expression(e))
+ return NULL;
+ expr->type = EXPR_BINOP;
+ expr->op = '+';
+ expr->ctype = size_t_ctype;
+ expr->left = copy;
+ expr->right = e;
+ }
+ return size_t_ctype;
+}
+
struct symbol *evaluate_expression(struct expression *expr)
{
if (!expr)
@@ -2688,6 +2769,9 @@ struct symbol *evaluate_expression(struct expression *expr)
expr->ctype = &type_ctype;
return &type_ctype;

+ case EXPR_OFFSETOF:
+ return evaluate_offsetof(expr);
+
/* These can not exist as stand-alone expressions */
case EXPR_INITIALIZER:
case EXPR_IDENTIFIER:
diff --git a/expand.c b/expand.c
index a46f1c2..c6d188e 100644
--- a/expand.c
+++ b/expand.c
@@ -968,6 +968,7 @@ static int expand_expression(struct expression *expr)
case EXPR_SIZEOF:
case EXPR_PTRSIZEOF:
case EXPR_ALIGNOF:
+ case EXPR_OFFSETOF:
expression_error(expr, "internal front-end error: sizeof in expansion?");
return UNSAFE;
}
diff --git a/expression.c b/expression.c
index a40ab2b..0108224 100644
--- a/expression.c
+++ b/expression.c
@@ -152,6 +152,69 @@ static struct token *builtin_types_compatible_p_expr(struct token *token,
return token;
}

+static struct token *builtin_offsetof_expr(struct token *token,
+ struct expression **tree)
+{
+ struct expression *expr = NULL;
+ struct expression **p = &expr;
+ struct symbol *sym;
+ int op = '.';
+
+ token = token->next;
+ if (!match_op(token, '('))
+ return expect(token, '(', "after __builtin_offset");
+
+ token = token->next;
+ token = typename(token, &sym);
+ if (sym->ident)
+ sparse_error(token->pos,
+ "type expression should not include identifier "
+ "\"%s\"", sym->ident->name);
+
+ if (!match_op(token, ','))
+ return expect(token, ',', "in __builtin_offset");
+
+ while (1) {
+ struct expression *e;
+ switch (op) {
+ case ')':
+ expr->in = sym;
+ *tree = expr;
+ default:
+ return expect(token, ')', "at end of __builtin_offset");
+ case SPECIAL_DEREFERENCE:
+ e = alloc_expression(token->pos, EXPR_OFFSETOF);
+ e->op = '[';
+ *p = e;
+ p = &e->down;
+ /* fall through */
+ case '.':
+ token = token->next;
+ e = alloc_expression(token->pos, EXPR_OFFSETOF);
+ e->op = '.';
+ if (token_type(token) != TOKEN_IDENT) {
+ sparse_error(token->pos, "Expected member name");
+ return token;
+ }
+ e->ident = token->ident;
+ token = token->next;
+ break;
+ case '[':
+ token = token->next;
+ e = alloc_expression(token->pos, EXPR_OFFSETOF);
+ e->op = '[';
+ token = parse_expression(token, &e->index);
+ token = expect(token, ']',
+ "at end of array dereference");
+ if (!e->index)
+ return token;
+ }
+ *p = e;
+ p = &e->down;
+ op = token_type(token) == TOKEN_SPECIAL ? token->special : 0;
+ }
+}
+
static struct token *string_expression(struct token *token, struct expression *expr)
{
struct string *string = token->string;
@@ -359,6 +422,10 @@ struct token *primary_expression(struct token *token, struct expression **tree)
token = builtin_types_compatible_p_expr(token, &expr);
break;
}
+ if (token->ident == &__builtin_offsetof_ident) {
+ token = builtin_offsetof_expr(token, &expr);
+ break;
+ }
} else if (sym->enum_member) {
expr = alloc_expression(token->pos, EXPR_VALUE);
*expr = *sym->initializer;
diff --git a/expression.h b/expression.h
index 1bf02c4..19e0302 100644
--- a/expression.h
+++ b/expression.h
@@ -44,6 +44,7 @@ enum expression_type {
EXPR_POS, // position in initializer
EXPR_FVALUE,
EXPR_SLICE,
+ EXPR_OFFSETOF,
};

struct expression {
@@ -127,6 +128,15 @@ struct expression {
unsigned int init_offset, init_nr;
struct expression *init_expr;
};
+ // EXPR_OFFSETOF
+ struct {
+ struct symbol *in;
+ struct expression *down;
+ union {
+ struct ident *ident;
+ struct expression *index;
+ };
+ };
};
};

diff --git a/ident-list.h b/ident-list.h
index 0f654bf..b183eac 100644
--- a/ident-list.h
+++ b/ident-list.h
@@ -29,6 +29,7 @@ IDENT(asm); IDENT_RESERVED(__asm); IDENT_RESERVED(__asm__);
IDENT(alignof); IDENT_RESERVED(__alignof); IDENT_RESERVED(__alignof__);
IDENT_RESERVED(__sizeof_ptr__);
IDENT_RESERVED(__builtin_types_compatible_p);
+IDENT_RESERVED(__builtin_offsetof);

/* Attribute names */
IDENT(packed); IDENT(__packed__);
diff --git a/inline.c b/inline.c
index f80403c..061261a 100644
--- a/inline.c
+++ b/inline.c
@@ -237,7 +237,23 @@ static struct expression * copy_expression(struct expression *expr)
expr->init_expr = val;
break;
}
-
+ case EXPR_OFFSETOF: {
+ struct expression *val = copy_expression(expr->down);
+ if (expr->op == '.') {
+ if (expr->down != val) {
+ expr = dup_expression(expr);
+ expr->down = val;
+ }
+ } else {
+ struct expression *idx = copy_expression(expr->index);
+ if (expr->down != val || expr->index != idx) {
+ expr = dup_expression(expr);
+ expr->down = val;
+ expr->index = idx;
+ }
+ }
+ break;
+ }
default:
warning(expr->pos, "trying to copy expression type %d", expr->type);
}
diff --git a/lib.c b/lib.c
index 7f6334c..7fea474 100644
--- a/lib.c
+++ b/lib.c
@@ -609,7 +609,6 @@ void create_builtin_stream(void)
add_pre_buffer("#define __builtin_va_arg_incr(x) ((x) + 1)\n");
add_pre_buffer("#define __builtin_va_copy(dest, src) ({ dest = src; (void)0; })\n");
add_pre_buffer("#define __builtin_va_end(arg)\n");
- add_pre_buffer("#define __builtin_offsetof(type, name) ((__SIZE_TYPE__)&((type *)(0ul))->name)\n");

/* FIXME! We need to do these as special magic macros at expansion time! */
add_pre_buffer("#define __BASE_FILE__ \"base_file.c\"\n");
diff --git a/show-parse.c b/show-parse.c
index 0bef01c..07ee763 100644
--- a/show-parse.c
+++ b/show-parse.c
@@ -1049,6 +1049,7 @@ int show_expression(struct expression *expr)
case EXPR_SIZEOF:
case EXPR_PTRSIZEOF:
case EXPR_ALIGNOF:
+ case EXPR_OFFSETOF:
warning(expr->pos, "invalid expression after evaluation");
return 0;
case EXPR_CAST:
--
1.5.0-rc2.GIT

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Next message: david: "Re: Dual-Licensing Linux Kernel with GPL V2 and GPL V3"
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