Re: [PATCH] Implement -fsanitize=float-cast-overflow (take 3)

[Konstantin Serebryany <konstantin dot s dot serebryany at gmail dot com>]

On Fri, May 23, 2014 at 6:35 PM, Konstantin Serebryany
<konstantin.s.serebryany@gmail.com> wrote:
> On Fri, May 23, 2014 at 6:28 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>> On Fri, May 23, 2014 at 04:19:00PM +0200, Marek Polacek wrote:
>>> This is the latest patch for -fsanitize=float-cast-overflow.  Since last
>>> version it:
>>> - adds tons of tests written by Jakub;
>>> - patches libubsan so it can handle 96-bit floating-point types
>>>   (that is, long double and __float80 in -m32 mode);
>>
>> CCing Kostya on this one liner, which has been posted to llvm-commits,
>> but nothing has been done yet.  I'm approving this anyway, I don't see
>> anything controversial on it and clang fails without that change the same
>> (supposedly insufficient test coverage on the compiler-rt side).
>
> ubsan is not my domain, but since the patch is so simple let me try to
> handle it.

http://llvm.org/viewvc/llvm-project?view=revision&revision=209516

>
>>
>>> - includes a hack for printing  __float{80,128}/_Decimal* types in
>>>   libubsan.  Since libubsan handles only float/double/long double
>>>   floating-point types, we use TK_Unknown for other types, meaning
>>>   that libubsan prints "<unknown>" instead of the value.
>>
>> I think this is for now good, while in theory I can imagine not very long
>> code to print _Decimal* to string (convert to binary integer format if
>> in the densely packed format (hey, ppc*), print __int128 significand
>> (or do 2x wide long long division/modulo) into string using snprintf,
>> take care of exponent and sign and putting in decimal dot), it is not high
>> prio for me, and for __float128 you can hardly avoid libquadmath or
>> something similarly large, unless you want to print it as C99 hexadecimal
>> float (that would be again pretty easy).
>>
>>> Regtested/bootstrapped on x86_64-linux.  Couldn't test ppc64, as
>>> libsanitizer currently doesn't build on this architecture.
>>>
>>> Ok for trunk?
>>>
>>> 2014-05-23  Marek Polacek  <polacek@redhat.com>
>>>           Jakub Jelinek  <jakub@redhat.com>
>>>
>>>       * builtins.def: Change SANITIZE_FLOAT_DIVIDE to SANITIZE_NONDEFAULT.
>>>       * gcc.c (sanitize_spec_function): Likewise.
>>>       * convert.c (convert_to_integer): Include "ubsan.h".  Add
>>>       floating-point to integer instrumentation.
>>>       * doc/invoke.texi: Document -fsanitize=float-cast-overflow.
>>>       * flag-types.h (enum sanitize_code): Add SANITIZE_FLOAT_CAST and
>>>       SANITIZE_NONDEFAULT.
>>>       * opts.c (common_handle_option): Handle -fsanitize=float-cast-overflow.
>>>       * sanitizer.def (BUILT_IN_UBSAN_HANDLE_FLOAT_CAST_OVERFLOW,
>>>       BUILT_IN_UBSAN_HANDLE_FLOAT_CAST_OVERFLOW_ABORT): Add.
>>>       * ubsan.c: Include "realmpfr.h" and "dfp.h".
>>>       (get_ubsan_type_info_for_type): Handle REAL_TYPEs.
>>>       (ubsan_type_descriptor): Set tkind to 0xffff for types other than
>>>       float/double/long double.
>>>       (ubsan_instrument_float_cast): New function.
>>>       * ubsan.h (ubsan_instrument_float_cast): Declare.
>>> testsuite/
>>>       * c-c++-common/ubsan/float-cast-overflow-1.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-10.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-2.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-3.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-4.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-5.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-6.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-7.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-7.h: New file.
>>>       * c-c++-common/ubsan/float-cast-overflow-8.c: New test.
>>>       * c-c++-common/ubsan/float-cast-overflow-9.c: New test.
>>>       * c-c++-common/ubsan/float-cast.h: New file.
>>>       * g++.dg/ubsan/float-cast-overflow-bf.C: New test.
>>>       * gcc.dg/ubsan/float-cast-overflow-bf.c: New test.
>>> libsanitizer/
>>>       * ubsan/ubsan_value.cc (getFloatValue): Handle 96-bit
>>>       floating-point types.
>>
>> Ok, thanks.
>>
>>         Jakub