Comment 3 for bug 1694644

Hi Tejas,

This is my first ever gcc contrib. I am not sure what you expect me to send to the patches email? Should I send the whole description to them again?

Thanks,
Reetesh

> On 31-May-2017, at 6:29 PM, Tejas Belagod <email address hidden> wrote:
>
> Hi Reetesh,
>
> Thanks for suggesting the patch.
>
> I suggest you post a patch against trunk to <email address hidden> and
> get it reviewed by GCOV maintainers upstream.
>
> 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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