This patch fixes a failure that happens when a structure has a static
member whose type is the same as itself. From the bug report:
Example code:
struct A
{
static A Empty;
int a;
};
int main(void) {
A a;
return 0;
}
Output:
(gdb) ptype/o A
/* offset | size */ type = struct A {
static struct A {
static struct A {
static struct A {
static struct A {
static struct A {
static struct A {
... # infinite loop
The problem here is that GDB is not taking into account the fact that
static members inside a class/struct are not stored in the
class/struct, and therefore they should not be accounted for during
the display of the offsets/sizes. The fix is simple: we just check if
the field we're dealing with (on
c-typeprint.c:c_type_print_base_struct_union) is static, and if it is
then we don't iterate over it.
This patch also adds a new test for this case, and doesn't introduce
any regressions. I believe it is important enough to be included in
the 8.2 branch.
OK?
gdb/ChangeLog:
2018-07-11 Sergio Durigan Junior <sergiodj@redhat.com>
PR c++/23373
* c-typeprint.c (c_type_print_base_struct_union): Don't print
offsets/sizes for static members of a class/struct.
gdb/testsuite/ChangeLog:
2018-07-11 Sergio Durigan Junior <sergiodj@redhat.com>
PR c++/23373
* gdb.base/ptype-offsets.cc (struct static_member): New
struct.
(main) <stmember>: New variable.
* gdb.base/ptype-offsets.exp: Add test for printing a struct
with a static member in it.
This commit implements the pahole-like '/o' option for 'ptype', which
prints the offsets and sizes of struct fields, reporting whenever
there is a hole found.
The output is heavily based on pahole(1), with a few modifications
here and there to adjust it to our reality. Here's an example:
/* offset | size */ type = struct wer : public tuv {
public:
/* 32 | 24 */ struct tyu {
/* 32:31 | 4 */ int a1 : 1;
/* 32:28 | 4 */ int a2 : 3;
/* 32: 5 | 4 */ int a3 : 23;
/* 35: 3 | 1 */ char a4 : 2;
/* XXX 3-bit hole */
/* XXX 4-byte hole */
/* 40 | 8 */ int64_t a5;
/* 48:27 | 4 */ int a6 : 5;
/* 48:56 | 8 */ int64_t a7 : 3;
/* total size (bytes): 24 */
} a1;
/* total size (bytes): 56 */
}
A big part of this patch handles the formatting logic of 'ptype',
which is a bit messy. The code to handle bitfield offsets, however,
took some time to craft. My thanks to Pedro Alves for figuring things
out and pointing me to the right direction, as well as coming up with
a way to inspect the layout of structs with bitfields (see testcase
for comments).
After many discussions both on IRC and at the mailing list, I tried to
implement printing vtables and inherited classes. Unfortunately the
code grew too complex and there were still a few corner cases failing
so I had to drop the attempt. This should be implemented in a future
patch.
This patch is the start of a long-term work I'll do to flush the local
patches we carry for Fedora GDB. In this specific case, I'm aiming at
upstreaming the feature implemented by the 'pahole.py' script that is
shipped with Fedora GDB:
<https://src.fedoraproject.org/rpms/gdb/blob/master/f/gdb-archer.patch#_311>
This has been regression-tested on the BuildBot. There's a new
testcase for it, along with an update to the documentation. I also
thought it was worth mentioning this feature in the NEWS file.
gdb/ChangeLog:
2017-12-15 Sergio Durigan Junior <sergiodj@redhat.com>
Pedro Alves <palves@redhat.com>
PR cli/16224
* NEWS (Changes since GDB 8.0): Mention new '/o' flag.
* c-typeprint.c (OFFSET_SPC_LEN): New define.
(c_type_print_varspec_prefix): New argument 'struct
print_offset_data *'.
(c_type_print_base_1): New function and prototype.
(c_print_type_1): New function, with code from 'c_print_type'.
(c_print_type): Use 'c_print_type_1'.
(c_type_print_varspec_prefix): New argument 'struct
print_offset_data *'. Use it. Call 'c_type_print_base_1'
instead of 'c_print_type_base'.
(print_spaces_filtered_with_print_options): New function.
(output_access_specifier): Take new argument FLAGS. Modify
function to call 'print_spaces_filtered_with_print_options'.
(c_print_type_vtable_offset_marker): New function.
(c_print_type_union_field_offset): New function.
(c_print_type_struct_field_offset): New function.
(c_print_type_no_offsets): New function.
(c_type_print_base_struct_union): New argument 'struct
print_offset_data *'. Print offsets and sizes for
struct/union/class fields.
* typeprint.c (const struct type_print_options
type_print_raw_options): Initialize 'print_offsets'.
(static struct type_print_options default_ptype_flags):
Likewise.
(struct print_offset_data print_offset_default_data): New
variable.
(whatis_exp): Handle '/o' option.
(_initialize_typeprint): Add '/o' flag to ptype's help.
* typeprint.h (struct print_offset_data): New struct.
(struct type_print_options) <print_offsets>: New field.
gdb/testsuite/ChangeLog:
2017-12-15 Sergio Durigan Junior <sergiodj@redhat.com>
PR cli/16224
* gdb.base/ptype-offsets.cc: New file.
* gdb.base/ptype-offsets.exp: New file.
gdb/doc/ChangeLog:
2017-12-15 Sergio Durigan Junior <sergiodj@redhat.com>
PR cli/16224
* gdb.texinfo (ptype): Add documentation for new flag '/o'.
Sergio Durigan Junior
Joel Brobecker