RUN_UNDER_VALGRIND statistics for GCC 7

["Martin Liška" <mliska@suse.cz>]

Hello.

I've tried to apply the same patch for the current trunk and tried to separate
reported errors to a different categories by a simple script ([1]).

There are number (complete report: [2]):

SECTION: gfortran 
  error types: 3534, total errors: 113282
  error types: 90.15%, total errors: 27.11%
SECTION: c++ 
  error types: 161, total errors: 7260
  error types: 4.11%, total errors: 1.74%
SECTION: c 
  error types: 90, total errors: 6320
  error types: 2.30%, total errors: 1.51%
SECTION: c-common 
  error types: 39, total errors: 205033
  error types: 0.99%, total errors: 49.06%
SECTION: Other 
  error types: 96, total errors: 86037
  error types: 2.45%, total errors: 20.59%

Type in the dump means a back trace, while 'total errors' represent total # of errors.
The second line shows a percentage ratio compared to all errors seen.

As seen fortran has very big variety of back traces. Well, it shows that we have multiple PRs reported,
they are references in the following PR: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68800

C++ FE looks quite good, same as C. c-common contains very interesting group:

are possibly lost: 204032 occurences
  malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
  xmalloc (xmalloc.c:148)
  new_buff (lex.c:3158)
  _cpp_get_buff (lex.c:3191)
  cpp_create_reader(c_lang, ht*, line_maps*) (init.c:251)
  c_common_init_options(unsigned int, cl_decoded_option*) (c-opts.c:219)
  toplev::main(int, char**) (toplev.c:2070)
  main (main.c:39)

(which is in fact majority of errors in the section). That's something I'm going to look at.

The last category (called Other) is dominated by

are definitely lost: 20740 occurences
  calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
  xcalloc (xmalloc.c:163)
  main (collect2.c:975)

which is probably option handling allocation stuff. Apart from that, there are just ~90 types of different
back traces. It's doable to remove majority of these in this stage1. OTOH as I'm not familiar with a FE (mainly Fortran),
solving Fortran FE would be not trivial.

Note: The dump comes from one week old build.

Martin

[1] https://github.com/marxin/script-misc/blob/master/valgrind-grep.py
[2] https://drive.google.com/open?id=0B0pisUJ80pO1M1VOd2pObUVXSEU