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

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).

> - 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  <>
> 	    Jakub Jelinek  <>
> 	* 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
> 	* opts.c (common_handle_option): Handle -fsanitize=float-cast-overflow.
> 	* 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/ (getFloatValue): Handle 96-bit
> 	floating-point types.

Ok, thanks.


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