ppapi: Work around a compiler bug where the PPP_Printing_Dev struct is not zeroed out.

ppapi: Work around a compiler bug where the PPP_Printing_Dev struct is not zeroed out.

BUG=83761
TEST=Print preview always work on Mac

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86676

[Lei Zhang, 2011-05-25 07:09:03]

Take this program, build it with g++ 4.4 and run it under Valgrind. You should
get:

(nil)
(nil)
(nil)
(nil)
0x41414141
0x41414141

repeat with g++ 4.2, and you'll get:

0x41414141
0x41414141
0x41414141
0x41414141
0x41414141
0x41414141

X_X

---

#include <stdio.h>

struct foo {
  void (*Foo)();
  void (*Bar)();
  void (*Qux)();
  void (*Baz)();
};

struct bar : public foo {
  bar() : foo() {
  }

  void (*Quux)();
  void (*Corge)();
};

int main() {
  bar* bbb = new bar;
  printf("%p\n", bbb->Foo);
  printf("%p\n", bbb->Bar);
  printf("%p\n", bbb->Qux);
  printf("%p\n", bbb->Baz);
  printf("%p\n", bbb->Quux);
  printf("%p\n", bbb->Corge);
}

[dmichael(do not use this one), 2011-05-25 13:30:28]

Egads, thanks for finding that. Is it 4.2 or just 4.2 on Darwin, I wonder.
Not important.

LGTM

On May 25, 2011 1:09 AM, <thestig@chromium.org> wrote:
>
> Reviewers: dmichael1, piman,
>
> Message:
> Take this program, build it with g++ 4.4 and run it under Valgrind. You
should
> get:
>
> (nil)
> (nil)
> (nil)
> (nil)
> 0x41414141
> 0x41414141
>
> repeat with g++ 4.2, and you'll get:
>
> 0x41414141
> 0x41414141
> 0x41414141
> 0x41414141
> 0x41414141
> 0x41414141
>
> X_X
>
> ---
>
> #include <stdio.h>
>
> struct foo {
>  void (*Foo)();
>  void (*Bar)();
>  void (*Qux)();
>  void (*Baz)();
> };
>
> struct bar : public foo {
>  bar() : foo() {
>  }
>
>  void (*Quux)();
>  void (*Corge)();
> };
>
> int main() {
>  bar* bbb = new bar;
>  printf("%p\n", bbb->Foo);
>  printf("%p\n", bbb->Bar);
>  printf("%p\n", bbb->Qux);
>  printf("%p\n", bbb->Baz);
>  printf("%p\n", bbb->Quux);
>  printf("%p\n", bbb->Corge);
> }
>
>
> Description:
> ppapi: Work around a compiler bug where the PPP_Printing_Dev struct is not
> zeroed out.
>
> BUG=83761
> TEST=Print preview always work on Mac
>
> Please review this at http://codereview.chromium.org/7031044/
>
> SVN Base: svn://chrome-svn/chrome/trunk/src/
>
> Affected files:
>  M     webkit/plugins/ppapi/ppapi_plugin_instance.h
>
>
> Index: webkit/plugins/ppapi/ppapi_plugin_instance.h
> ===================================================================
> --- webkit/plugins/ppapi/ppapi_plugin_instance.h        (revision 86566)
> +++ webkit/plugins/ppapi/ppapi_plugin_instance.h        (working copy)
> @@ -427,8 +427,12 @@
>     PPP_Printing_Dev_Combined(const PPP_Printing_Dev_0_3& old_if)
>         : PPP_Printing_Dev(),  // NOTE: The parens are important, to zero-
>                                // initialize the struct.
> +                               // Except older version of g++ doesn't!
> +                               // So do it explicitly in the ctor.
>           QuerySupportedFormats_0_3(old_if.QuerySupportedFormats),
>           Begin_0_3(old_if.Begin) {
> +      QuerySupportedFormats = NULL;
> +      Begin = NULL;
>       PrintPages = old_if.PrintPages;
>       End = old_if.End;
>     }
> @@ -439,7 +443,6 @@
>     // The 0.3 version of 'Begin'.
>     int32_t (*Begin_0_3)(PP_Instance instance,
>                          const struct PP_PrintSettings_Dev_0_3*
print_settings);
> -
>   };
>   scoped_ptr<PPP_Printing_Dev_Combined> plugin_print_interface_;
>
>
>

[piman, 2011-05-25 15:48:49]

LGTM

[commit-bot: I haz the power, 2011-05-25 18:14:41]

Commit queue patch verification failed

[commit-bot: I haz the power, 2011-05-25 19:36:17]

Change committed as 86676