[Clang][counted_by] Add support for 'counted_by' on struct pointers #127116
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The 'counted_by' attribute is now available for structs. It generates
code for sanity checks as well as __builtin_dynamic_object_size()
calculations. For example:
struct annotated_ptr {
int count;
char *buf __counted_by(count);
};
'counted_by' cannot be applied to a pointer to an incomplete type. So
this is invalid:
struct foo;
struct annotated_ptr {
int count;
struct foo *buf __counted_by(count); /* invalid */
};
The 'count' field member may occur after the pointer. If it does, use
the '-fexperimental-late-parse-attributes' flag (which will hopefully be
made the default in future Clang versions).
Signed-off-by: Bill Wendling <morbo@google.com>
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
We automatically add the appropriate argument to the function call. The
function must be marked either 'pure' or 'const'. There's a small issue
still if the function is marked as 'static'. If it is, add the 'used'
attribute to it.
An example of use:
const unsigned long size = 42;
static const unsigned long inline __attribute__((__pure__, __used__)) buf_size(void *ptr);
struct X {
unsigned int flags;
int *buf __attribute__((counted_by(buf_size)));
int count;
/* int *buf2 __attribute__((counted_by(buf_size((void *)0)))); */
} *ptr;
static const unsigned long inline __attribute__((__pure__, __used__)) buf_size(void *ptr) {
struct X *p = (struct X *)ptr;
return p->count + size;
}
int __attribute__((__noinline__)) foo(struct X *ptr, int index) {
return ptr->buf[index];
}
int main(void) {
struct X p;
p.buf = __builtin_malloc(sizeof(int) * size + 37);
p.count = 37;
p.buf[3] = 927;
__builtin_printf("output = %d\n", foo(&p, 3));
return 0;
}
…ction definition.
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The 'counted_by' attribute is now available for structs. It generates code for sanity checks as well as __builtin_dynamic_object_size() calculations. For example:
struct annotated_ptr {
int count;
char *buf __counted_by(count);
};
'counted_by' cannot be applied to a pointer to an incomplete type. So this is invalid:
struct foo;
struct annotated_ptr {
int count;
struct foo buf __counted_by(count); / invalid */
};
The 'count' field member may occur after the pointer. If it does, use the '-fexperimental-late-parse-attributes' flag (which will hopefully be made the default in future Clang versions).