Do not open .gcda/.gcno files in write mode unnecessarily.

[Neil Vachharajani]

Ping?

On Tue, Sep 22, 2009 at 10:01 AM, Neil Vachharajani <nvachhar@google.com> wrote:
> On Tue, Sep 22, 2009 at 5:26 AM, Nathan Sidwell <nathan@codesourcery.com> wrote:
>> Neil Vachharajani wrote:
>>>
>>> GCC currently always opens .gcda/.gcno files in write mode.  This
>>> leads to permission denied errors when opening these files if the
>>> files are read-only.  Having read-only .gcda files is useful to ensure
>>> that one does not unintentionally modify profile data (by default, an
>>> instrumented binary will append to .gcda files).  This patch modifies
>>> the behavior of gcov_open to only open the file in write mode if the
>>> MODE argument is >= 0.
>>>
>>> Bootstrapped/regtested on x86_64-linux and i686-linux.  Verified that
>>> FDO still works.  Ok for trunk?
>>>
>>> 2009-09-17  Neil Vachharajani  <nvachhar@gmail.com>
>>>
>>>        * gcov-io.c (gcov_open): Open files read-only when MODE < 0
>>
>> Can you protect the new read-only code with #if !IN_LIBGCOV, so we don't
>> unnecessarily bloat that?  It looks like that's the locking calls as the
>> open call is already in such a #if block.
>
> I'm not quite sure I follow.  While the textual change looks large,
> the patch changes only 2 things.  First, if GCOV_LOCKED is true, then
> s_flock.l_type is set conditionally rather than unconditionally (note
> the if statement guarding that assignment already existed guarding two
> different calls to open).  Second, instead of always passing "r+b" to
> fopen (or fdopen) the parameter is now selected with ?: on mode.
>
> If IN_LIBGCOV is true, mode is set to 0 in the function itself (mode
> is not an argument in that case).  I believe that this constant will
> be propagated to all the conditions on mode and the generated code
> will not at all be bloated by the read-only code as it will be dead
> code eliminated away.
>
> Apologies in advance if I am missing something
>
> Neil
>
>>
>> nathan
>>
>> --
>> Nathan Sidwell    ::   http://www.codesourcery.com   ::         CodeSourcery
>>
>>
>
>
>
> --
> Neil Vachharajani
> Google
> 650-214-1804
>



-- 
Neil Vachharajani
Google
650-214-1804