r177164 - Force column info only for direct inlined functions. This should strike

[Adrian Prantl]

On Mar 15, 2013, at 11:26 AM, David Blaikie <dblaikie at gmail.com> wrote:

> On Fri, Mar 15, 2013 at 10:46 AM, Adrian Prantl <aprantl at apple.com> wrote:
>> 
>> On Mar 15, 2013, at 10:25 AM, David Blaikie <dblaikie at gmail.com> wrote:
>> 
>>> On Fri, Mar 15, 2013 at 10:09 AM, Adrian Prantl <aprantl at apple.com> wrote:
>>>> Author: adrian
>>>> Date: Fri Mar 15 12:09:05 2013
>>>> New Revision: 177164
>>>> 
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=177164&view=rev
>>>> Log:
>>>> Force column info only for direct inlined functions. This should strike
>>>> the balance between expected behavior and compatibility with the gdb
>>>> testsuite.
>>>> 
>>>> (GDB gets confused if we break an expression into multiple debug
>>>> stmts so we enable this behavior only for inlined functions. For the
>>>> full experience people can still use -gcolumn-info.)
>>> 
>>> I'm not sure I understand how this will address the issue... Perhaps
>>> I'm misunderstanding something about this change. I have a few
>>> questions/uncertainties:
>> 
>>> 1) You can't really determine in the frontend if a function will
>>> actually be inlined - trying to predicate debug info on that seems
>>> like we'll get surprising/varying debug behavior based on whether the
>>> backend chooses to inline the function
>> 
>> That is correct. My thinking was that the backend would only inline at >O0 and if you need more precise debug info you could always use -gcolumn-info. But for those cases where function is inlined at O0 (which happens for inline-attributed functions and is done by the frontend) users will get the expected behavior.
>> This is not very elegant, but I’m trying to find a middle ground between not breaking gdb’s testsuite and fixing the debug experience for inlined functions.
> 
> Sure - I'm not suggesting that we should not fix the original bug you
> set out to fix, just that the solution that Eric & I were
> discussing/suggesting wasn't what you've implemented here. I thought
> what we were discussing was changing the backend to not emit separate
> line table entries when the line is the same but the column is
> different. This would be consistent with the debug experience users
> expect (given GDB's lack of column information) in all cases, no
> matter what things were inlined or not inlined, if I'm not mistaken.

As I mentioned earlier, the problem is that for inlined functions we need to do exactly that otherwise a breakpoint at the inlined function (appearing twice on one line) would be hit only once.

— adrian