Date: Sat, 12 Aug 2017 14:53:48 -0700 From: "Ngie Cooper (yaneurabeya)" <yaneurabeya@gmail.com> To: Ryan Libby <rlibby@FreeBSD.org> Cc: Ian Lepore <ian@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org, Bruce Evans <brde@optusnet.com.au> Subject: Re: svn commit: r322418 - head/lib/msun/src Message-ID: <A6C8FE24-3458-474D-B05D-FEABFFF7F6EB@gmail.com> In-Reply-To: <5672BE7A-0640-4C8B-9B41-44AD83D7B59E@gmail.com> References: <201708112241.v7BMfP5X028262@repo.freebsd.org> <1502555191.47886.30.camel@freebsd.org> <CAHgpiFx=pDQA-dHNQJwqDQ%2B2iXJDkvVNsdmyBZG2EL%2BVJQCU4g@mail.gmail.com> <CAHgpiFwAAs8=pcpuwVCx-hNdPp3OXFESVdZ6=9fJ8kPwZiqVCg@mail.gmail.com> <5672BE7A-0640-4C8B-9B41-44AD83D7B59E@gmail.com>
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> On Aug 12, 2017, at 14:45, Ngie Cooper (yaneurabeya) <yaneurabeya@gmail.com> wrote:
>
>>
>> On Aug 12, 2017, at 10:55, Ryan Libby <rlibby@FreeBSD.org> wrote:
>
> …
>
>> A few possible quick fixes:
>>
>> - Change the {arm64,riscv,sparc64}/include/float.h LDBL_MAX_EXP
>> definitions from (+16384) to 16384.
>>
>> - Change HALF_LDBL_MAX from
>> #define HALF_LDBL_MAX __CONCAT(__CONCAT(0x0.8p, LDBL_MAX_EXP), L)
>> to
>> #if LDBL_MAX_EXP != 0x4000
>> #error "Unsupported long double format"
>> #endif
>> #define HALF_LDBL_MAX 0x0.8p16384L
>>
>> - Change the HALF_LDBL_MAX constant to a variable constructed with
>> LD80C(), I think with
>> LD80C(0x8000000000000000, 16383, 5.9486574767861588254e+4931L)
>> but this also requires #error for LDBL_MAX_EXP != 0x4000, so not
>> really any better than the above.
>>
>> I think I will back the patch out for now and go back to review.
>
> The issue is an inconsistency with how LDBL_MAX_EXP is defined in the MD headers:
* is an -> is due to an
> $ grep -r LDBL_MAX_EXP sys/sparc64/
> sys/sparc64/include/float.h:#define LDBL_MAX_EXP (+16384)
> $ grep -r LDBL_MAX_EXP sys/x86/
> sys/x86/include/float.h:#define LDBL_MAX_EXP 16384
Here are the full gamut of definitions for LDBL_MAX_EXP. It seems that sparc64 isn’t the only architecture using this pattern:
$ grep -r DBL_MAX_EXP sys/*/include
sys/arm/include/float.h:#define DBL_MAX_EXP 1024
sys/arm/include/float.h:#define LDBL_MAX_EXP DBL_MAX_EXP
sys/arm64/include/float.h:#define DBL_MAX_EXP 1024
sys/arm64/include/float.h:#define LDBL_MAX_EXP (+16384)
sys/mips/include/float.h:#define DBL_MAX_EXP 1024
sys/mips/include/float.h:#define LDBL_MAX_EXP DBL_MAX_EXP
sys/powerpc/include/float.h:#define DBL_MAX_EXP 1024
sys/powerpc/include/float.h:#define LDBL_MAX_EXP DBL_MAX_EXP
sys/riscv/include/float.h:#define DBL_MAX_EXP 1024
sys/riscv/include/float.h:#define LDBL_MAX_EXP (+16384)
sys/sparc64/include/float.h:#define DBL_MAX_EXP 1024
sys/sparc64/include/float.h:#define LDBL_MAX_EXP (+16384)
sys/x86/include/float.h:#define DBL_MAX_EXP 1024
sys/x86/include/float.h:#define LDBL_MAX_EXP 16384
It might also be an inconsistency with how clang vs gcc [4.2.1] handles __CONCAT, and what -std= flags are passed to ${CC} in the Makefile, since the implementation is predicated by whether or not it’s C++ or __STDC__ is defined. There might be an update that we can grab from NetBSD (since the macro originated there).
I don’t understand [right now] why the (+foo) form is used *shrugs*.
Cheers,
-Ngie
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