Hi,

I talked to the gcc team. The summary of the discussion is:

My patch works around the core issue of circular lists being created. It's not a fix in the sense it does not prevent the circular lists from getting formed. I was told to find the root cause of what created the circular lists and provide a patch for that.

Sadly I have not had time to spend on this new investigation.

Meanwhile, using the whole mechanism I have provided in GitHub is something we can use, if that's any help.

Thanks
Reetesh

> On 11-Sep-2017, at 6:54 PM, Tejas Belagod <email address hidden> wrote:
> 
> Hi eDeviser,
> 
> I think it was Reetesh Ranjan's patch (see above) - I don't know if he
> managed to get it submitted upstream to the gcc lists.
> 
> Thanks,
> Tejas.
> 
> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1694644
> 
> Title:
>  Infinite loop in gcov_exit
> 
> Status in GNU ARM Embedded Toolchain:
>  New
> 
> Bug description:
>  Release version: 5-2016-q3-update
>  Using binary package
>  Host: Mac OSX, Windows
> 
>  All other mandatory details are available in the description below:
> 
>  I was trying to do code coverage for my embedded project using
>  5-2016-q3-update and GNU ARM Eclipse
>  (http://gnuarmeclipse.github.io/). I broadly followed the concept of
>  manually breaking into 'gcov_exit' and using 'gdb dump binary' to
>  create the gcda files, as described in
>  https://mcuoneclipse.com/2014/12/26/code-coverage-for-embedded-target-
>  with-eclipse-gcc-and-gcov/. However; gcov_exit hanged infinitely. For
>  a simple project of not more than 25 source files, it would take
>  minutes and won't return. To debug this, I made a copy of respective
>  gcc and libgcc code and tailored it as needed and plugged it into my
>  project so that I could see what the hang is about. It turned out that
>  the 1st instance of these loops "for (gi_ptr = list; gi_ptr; gi_ptr =
>  gi_ptr->next)" just won't finish. On debugging it appeared that the
>  list was circular and not a null-terminated one. I cannot figure it
>  out why that is as I studied gcc code, and __gcov_root.list
>  construction through __gcov_init does not seem to create any circular
>  lists. But it appeared to be so, because when I changed the loops to
>  expect a circular list rather than a null-terminated singly linked
>  list, things worked. Also, I manually debugged the functions called by
>  gcov_exit to see that there are exactly as many gcov_info nodes in the
>  __gcov_root.list as the number of source files covered, and the change
>  to expect a circular list made sense. I had to end up changing 3
>  instances of such loops and then I was able to generated the gcda
>  files.
> 
>  The ported/tailored version of the minimum gcc/libgcc code has been
>  made available at: https://github.com/reeteshranjan/libgcov-embedded
> 
>  I saw that the toolchain is based on
>  svn://gcc.gnu.org/svn/gcc/branches/ARM/; and I picked the code from
>  gcc trunk. However; it seems at least from embedded-6-branch onwards
>  that the gcov source is the same as I could see in gcc trunk that
>  time.
> 
>  I have also attached a patch I made using the embedded-6-branch which
>  clearly shows the for loop changes made.
> 
>  I also did a sample GNU ARM Eclipse project to use the above, which is available at:
>  https://github.com/reeteshranjan/libgcov-embedded-example
> 
>  Steps to reproduce and analyze:
>  - Setup any embedded project using GNU ARM Eclipse. Follow the steps in https://mcuoneclipse.com/2014/12/26/code-coverage-for-embedded-target-with-eclipse-gcc-and-gcov/ to generate coverage data by breaking into gcov_exit or __gcov_flush (whichever is available). The hang in gcov_exit should be reproducible.
>  - Now create another project from scratch without using the stub code as described in https://mcuoneclipse.com/2014/12/26/code-coverage-for-embedded-target-with-eclipse-gcc-and-gcov/
>  - Plugin https://github.com/reeteshranjan/libgcov-embedded using the instructions in README.md provided in this repository into the new project.
>  - In the port/libgcc/libgcov-driver.c file in the above, search for the loops "for (gi_ptr = list; gi_ptr && !(gi_ptr == list && break_loop_counter); gi_ptr = gi_ptr->next, break_loop_counter++)". These are the changes to expect a circular list and not a null-terminated singly linked list. Change these lines to how they are in original gcc code which is "for (gi_ptr = list; gi_ptr; gi_ptr = gi_ptr->next)"
>  - Follow the README instructions on how to break in gcov-io.c to use gdb instructions to manually create gcda files. You won't hit this breakpoint because of the hang in first of these for loops in 'compute_summary' function (now reproducible as we changed the code to use the original libgcc version)
>  - Now revert the for loop changes back
>  - Now the breakpoints should hit once for each source file
> 
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