Re: [patch] ptype: show members of an unnamed struct inside an union

Carlos Eduardo Seo
2007-08-24T16:02:00Z

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Joel

Here's a testcase. In order to see the issue, do the following:

1. Compile it with -g flag
2. Run gdb
3. b main
4. ptype struct my_page

You'll see:

type = struct my_page {
union {
struct {...};
};
}

Using the proposed patch, you'll see:

type = struct my_page {
union {
struct {int mapping; };
};
}

If you want, you may use a more complex union, such as:

struct my_page {
union {
struct {
int mapping;
long foo;
char *pointer;
};
struct {
char blah;
int test;
};
struct {
char blahblah;
};
struct {
};
};
};

Any questions, feel free to contact me.

Thanks and regards,

- --
Carlos Eduardo Seo
Software Engineer
IBM Linux Technology Center

Joel Brobecker wrote:
> Carlos,
>
>> The attached patched fixes an issue described on this post:
>>
>> http://sourceware.org/ml/gdb-patches/2002-04/msg01114.html
>
>> 2007-08-16 Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
>>
>> gdb/c-typeprint.c (c_type_print_base): check value of
>> TYPE_NFIELDS (type) when displaying members of an
>> unnamed struct inside an union.
>
> Could you add a testcase for this issue? Being new at reviewing
> other people's patches, it's sometimes hard for me to understand
> what you are trying to do. A testcase would help in two ways: not
> only ensure that we do not regress in the future, but also help
> me understand clearly what it is that we're trying to fix.
>
> Thank you!
>
>> Index: src-git/gdb/c-typeprint.c
>> ===================================================================
>> --- src-git.orig/gdb/c-typeprint.c 2007-08-16 15:28:04.000000000 -0700
>> +++ src-git/gdb/c-typeprint.c 2007-08-16 15:29:07.000000000 -0700
>> @@ -735,7 +735,7 @@
>> fputs_filtered (" ", stream);
>> }
>> wrap_here (" ");
>> - if (show < 0)
>> + if ((show < 0) && (TYPE_NFIELDS (type) == 0))
>> {
>> /* If we just printed a tag name, no need to print anything
else. */
>> if (TYPE_TAG_NAME (type) == NULL)
>

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struct my_page {
union {
struct {
int mapping;
};
};
};

main()
{
struct my_page mypage;
}

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