Fix PR c++/23373: GDB hangs when printing a struct with a static member of itself
Commit Message
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:
yyyy-mm-dd 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:
yyyy-mm-dd 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.
---
gdb/c-typeprint.c | 2 +-
gdb/testsuite/gdb.base/ptype-offsets.cc | 8 ++++++++
gdb/testsuite/gdb.base/ptype-offsets.exp | 11 +++++++++++
3 files changed, 20 insertions(+), 1 deletion(-)
Comments
On 2018-07-07 05:26 PM, Sergio Durigan Junior wrote:
> 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?
Thanks, LGTM. It would make sense to have it in 8.2 I believe.
Simon
On Tuesday, July 10 2018, Simon Marchi wrote:
> On 2018-07-07 05:26 PM, Sergio Durigan Junior wrote:
>> 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?
>
> Thanks, LGTM. It would make sense to have it in 8.2 I believe.
Thanks, pushed to both master and 8.2:
16ff70ddd430b63ca4dd68bf1d52828f2ed4f030 (master)
ad3c631a762734c39b85086d20ba28940c2fc9b8 (8.2)
@@ -1168,7 +1168,7 @@ c_type_print_base_struct_union (struct type *type, struct ui_file *stream,
int newshow = show - 1;
- if (flags->print_offsets
+ if (!is_static && flags->print_offsets
&& (TYPE_CODE (TYPE_FIELD_TYPE (type, i)) == TYPE_CODE_STRUCT
|| TYPE_CODE (TYPE_FIELD_TYPE (type, i)) == TYPE_CODE_UNION))
{
@@ -177,6 +177,13 @@ struct asd
void *f16;
};
+/* See PR c++/23373. */
+
+struct static_member
+{
+ static static_member Empty;
+ int abc;
+};
int
main (int argc, char *argv[])
@@ -188,6 +195,7 @@ main (int argc, char *argv[])
struct tyu e;
struct asd f;
uint8_t i;
+ static_member stmember;
return 0;
}
@@ -328,3 +328,14 @@ gdb_test_multiple "$test" "$test" {
pass $test
}
}
+
+# Test that printing a struct with a static member of itself doesn't
+# get us into an infinite loop.
+gdb_test "ptype/o static_member" \
+ [multi_line \
+{/\* offset | size \*/ type = struct static_member \{} \
+{ static static_member Empty;} \
+{\/* 0 | 4 \*/ int abc;} \
+{} \
+{ /\* total size \(bytes\): 4 \*/} \
+{ \}}]