https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107952
Bug ID: 107952
Summary: tree-object-size: inconsistent size for flexible
arrays nested in structs
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: siddhesh at gcc dot gnu.org
Target Milestone: ---
With -fstrict-flex-arrays, there is a clearer definition of what constitutes
flexible array members, controlled by the frontend. tree-object-size however
doesn't seem to handle this well enough when the flex array is nested. e.g.:
typedef struct {
char pad;
char data[8];
} F2;
typedef struct {
unsigned pad;
F2 flex;
} S2;
#define NULL (void *) 0
__SIZE_TYPE__
nested_flexarray (__SIZE_TYPE__ n)
{
S2 *p = (S2 *) __builtin_malloc (n);
return __builtin_dynamic_object_size (p->flex.data, 1);
}
__SIZE_TYPE__
nested_flexarray2 (S2 *p)
{
return __builtin_dynamic_object_size (p->flex.data, 1);
}
The current behaviour is to treat data as a flex array and nested_flexarray
returns the size as if it were a flex array. nested_flexarray2 however returns
the subscripted size, thinking of it as a fixed array, which should not be the
expected behaviour with -fstrict-flex-arrays=0. Instead it should return -1
for maximum size and perhaps 8 as minimum size.
If F2 is changed to:
typedef struct {
char pad;
char data[0];
} F2;
the current behaviour ends up returning 0 in both cases, which is incorrect.
Again, it should return the size as if it were a flex array in nested_flexarray
and -1 for maximum size for nested_flexarray2.
I have a patch that does this, but I need to fix up tests that currently expect
older behaviour and wanted to get some consensus before I fixed them up.
