Re: [PATCH] gcov: Add __gcov_info_to_gdca()

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 20/11/2020 17:14, Sebastian Huber wrote:

> On 20/11/2020 16:25, Martin Liška wrote:
>
>>>> Apart from these 2 hooks, I bet you will also need gcov_position 
>>>> and gcov_seek functions,
>>>> can be seen in my sent patch.
>>> For what do I need them?
>>>
>>
>> I prefer the way with the 2 extra hooks.
>> Can you please prepare a patch where the newly added functions 
>> __gcov_info_to_gcda and __gcov_fn_info_to_gcda
>> will be used in libgcov (with the hooks equal to fopen and fwrite? 
>
> I am not really sure what I should do. Do you mean that 
> write_one_data() should be rewritten to use __gcov_info_to_gcda() with 
> hooks that use gcov_write_unsigned()?
>
> The write_one_data() also has a const struct gcov_summary *prg_p 
> pointer. What should an external user provide for this pointer? For 
> example &gi_ptr->summary?
>
> The write_one_data() has this code
>
>       if (fn_buffer && fn_buffer->fn_ix == f_ix)
>         {
>           /* Buffered data from another program.  */
>           buffered = 1;
>           gfi_ptr = &fn_buffer->info;
>           length = GCOV_TAG_FUNCTION_LENGTH;
>         }
>
> which uses a global variable
>
> /* buffer for the fn_data from another program.  */
> static struct gcov_fn_buffer *fn_buffer;
>
> For this handling we would need a new hook to do this:
>
>       if (buffered)
>         fn_buffer = free_fn_data (gi_ptr, fn_buffer, GCOV_COUNTERS);
>
> I don't know for what we need seek and position hooks.

Refactoring write_one_data() to use hooks requires that

gcov_write_counter()

gcov_write_tag_length()

gcov_write_summary()

move from gcc/gcov-io.c to libgcc/libgcov-buffer.c. They can be made 
static. I am not sure if the external symbols can be removed

/* In libgcov we need these functions to be extern, so prefix them with
    __gcov.  In libgcov they must also be hidden so that the instance in
    the executable is not also used in a DSO.  */
#define gcov_write_tag_length __gcov_write_tag_length
#define gcov_write_counter __gcov_write_counter
#define gcov_write_summary __gcov_write_summary

without breaking anything? What is the performance impact if only 
gcov_write_unsigned() is used by libgcc/libgcov-driver.c?

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