Re: [patch] [gdb/testsuite] include a use of the definition of a type to cause clang to emit debug info

[Doug Evans <dje at google dot com>]

On Wed, Apr 23, 2014 at 5:20 PM, Doug Evans <dje@google.com> wrote:
> David Blaikie writes:
>  > Clang has an optimization that causes a the debug info to only include
>  > the declaration of a type if the type is referenced but never used in
>  > a context that requires a definition (eg: pointers are handed around
>  > but never deferenced).
>  >
>  > This patch introduces a variable to one test file to cause clang to
>  > emit the full definition of the type as well as fixing up a related
>  > typo in the test message of the associated expect file.
>  >
>  > Like the difference between GCC and Clang in the emission of unused
>  > static entities, I think this case is also a matter of degrees - both
>  > GCC and Clang implement other similar optimizations* to the one
>  > outlined here and the GDB test suite has managed to pass without
>  > disabling those optimizations in GCC and I hope it's suitable to do
>  > the same for Clang.
>  >
>  > Though admittedly I don't have much of the context of the history of
>  > the testsuite, its priorities/preferences when it comes to
>  > distinguishing testing compiler behavior versus debugger behavior,
>  > etc.
>  >
>  > * the one I know of involves dynamic types: both GCC and Clang only
>  > emit the debug info definition of such a type in any translation unit
>  > that emits the key function. This means in many contexts where a full
>  > definition is provided in the source only a declaration is provided in
>  > the debug info.
>  > commit 1128f6fb45483d45668d09e0696f4a590334e0c4
>  > Author: David Blaikie <dblaikie@gmail.com>
>  > Date:   Sat Apr 12 23:27:19 2014 -0700
>  >
>  >     Cause clang to emit the definition of a type used only by pointer
>  >
>  >     gdb/testsuite/
>  >      * gdb.stabs/gdb11479.c: introduce a variable to cause clang to
>  >      emit the full definition of type required by the test
>  >      * gdb.stabs/gdb11479.exp: correct a typo in a test message
>
> ChangeLog conventions require one to document more specifically
> where the change occurred.  E.g.,
>
>         * gdb.stabs/gdb11479.c (tag_dummy_enum): New global to cause clang to
>         emit the full definition of type required by the test.
>         * gdb.stabs/gdb11479.exp (do_test): Correct a typo in a test message.
>
> Plus note the capitalization and period.
>
> Plus conventions also say to specify the "why" of things in source
> and not the changelog.  I realize we're not going to the trouble
> of adding comments to every non-static function to document why it
> has to be non-static.  So I don't see a great need to do so here,
> and I'd leave the ChangeLog entry as written.
> I'm just writing this down in case the topic comes up.
>
>  >
>  > diff --git gdb/testsuite/ChangeLog gdb/testsuite/ChangeLog
>  > index 730c116..07ba18e 100644
>  > --- gdb/testsuite/ChangeLog
>  > +++ gdb/testsuite/ChangeLog
>  > @@ -1,3 +1,9 @@
>  > +2014-04-12  David Blaikie  <dblaikie@gmail.com>
>  > +
>  > +        * gdb.stabs/gdb11479.c: introduce a variable to cause clang to
>  > +    emit the full definition of type required by the test
>  > +        * gdb.stabs/gdb11479.exp: correct a typo in a test message
>  > +
>
> Mix of tabs and spaces.  Just use tabs.
>
> Ok with those changes.

Bleah.  Sorry Joel.  I didn't see your earlier mail.

What do you think of adding a testcase that explicitly tests the
user's expectation?
[per Pedro's suggestion]