Module Name: src Committed By: riastradh Date: Thu Aug 1 02:06:31 UTC 2019
Modified Files: src/lib/libc/gdtoa: Makefile.inc gdtoa_fltrnds.h gdtoaimp.h Log Message: Honour the floating-point rounding mode in floating-point formatting. C99, Sec. 7.19.6.1 `The fprintf function', paragraph 13, p. 281: (Recommended practice) For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most DECIMAL_DIG, then the result should be correctly rounded. If the number of significant decimal digits is more than DECIMAL_DIG but the source value is exactly representable with DECIMAL_DIG digits, then the result should be an exact representation with trailing zeros. Otherwise, the source value is bounded by two adjacent decimal strings L < U, both having DECIMAL_DIG significant idgits; the value of the resultant decimal string D should satisfy L <= D <= U, _with the extra stipulation that the error should have a correct sign for the current rounding direction_. [emphasis added] The gdtoa code base already supports respecting the floating-point rounding mode, as long as we compile it with Honor_FLT_ROUNDS defined. However, for this to work, fegetround must be available in libc, which it is not currently -- the fenv logic is in libm. Fortunately, we don't have to move all of fenv from libm to libc -- programs that do not link against libm don't have fesetround, so the rounding mode is always the default (barring asm shenanigans that bypass the API -- tough). So use a weak reference to fegetround; by default, assume FE_TONEAREST if it is not defined. To generate a diff of this commit: cvs rdiff -u -r1.10 -r1.11 src/lib/libc/gdtoa/Makefile.inc cvs rdiff -u -r1.1.1.1 -r1.2 src/lib/libc/gdtoa/gdtoa_fltrnds.h cvs rdiff -u -r1.14 -r1.15 src/lib/libc/gdtoa/gdtoaimp.h Please note that diffs are not public domain; they are subject to the copyright notices on the relevant files.
Modified files: Index: src/lib/libc/gdtoa/Makefile.inc diff -u src/lib/libc/gdtoa/Makefile.inc:1.10 src/lib/libc/gdtoa/Makefile.inc:1.11 --- src/lib/libc/gdtoa/Makefile.inc:1.10 Thu Jan 16 20:31:42 2014 +++ src/lib/libc/gdtoa/Makefile.inc Thu Aug 1 02:06:31 2019 @@ -1,10 +1,14 @@ -# $NetBSD: Makefile.inc,v 1.10 2014/01/16 20:31:42 christos Exp $ +# $NetBSD: Makefile.inc,v 1.11 2019/08/01 02:06:31 riastradh Exp $ # gdtoa sources .PATH: ${.CURDIR}/gdtoa CPPFLAGS+=-I${.CURDIR}/gdtoa -I${.CURDIR}/locale +.if ${MACHINE_ARCH} == "vax" CPPFLAGS+=-DNO_FENV_H +.else +CPPFLAGS+=-DHonor_FLT_ROUNDS +.endif # machine-dependent directory must provide the following: # arith.h gd_qnan.h Index: src/lib/libc/gdtoa/gdtoa_fltrnds.h diff -u src/lib/libc/gdtoa/gdtoa_fltrnds.h:1.1.1.1 src/lib/libc/gdtoa/gdtoa_fltrnds.h:1.2 --- src/lib/libc/gdtoa/gdtoa_fltrnds.h:1.1.1.1 Sat Mar 19 16:26:37 2011 +++ src/lib/libc/gdtoa/gdtoa_fltrnds.h Thu Aug 1 02:06:31 2019 @@ -1,4 +1,5 @@ - FPI *fpi, fpi1; + CONST FPI *fpi; + FPI fpi1; int Rounding; #ifdef Trust_FLT_ROUNDS /*{{ only define this if FLT_ROUNDS really works! */ Rounding = Flt_Rounds; Index: src/lib/libc/gdtoa/gdtoaimp.h diff -u src/lib/libc/gdtoa/gdtoaimp.h:1.14 src/lib/libc/gdtoa/gdtoaimp.h:1.15 --- src/lib/libc/gdtoa/gdtoaimp.h:1.14 Fri Apr 19 10:41:53 2013 +++ src/lib/libc/gdtoa/gdtoaimp.h Thu Aug 1 02:06:31 2019 @@ -1,4 +1,4 @@ -/* $NetBSD: gdtoaimp.h,v 1.14 2013/04/19 10:41:53 joerg Exp $ */ +/* $NetBSD: gdtoaimp.h,v 1.15 2019/08/01 02:06:31 riastradh Exp $ */ /**************************************************************** @@ -200,6 +200,9 @@ THIS SOFTWARE. #include "gd_qnan.h" #ifdef Honor_FLT_ROUNDS #include <fenv.h> +__weakref_visible int __libc_fegetround_ref(void) __weak_reference(fegetround); +#define fegetround() \ + (__libc_fegetround_ref ? __libc_fegetround_ref() : FE_TONEAREST) #endif #ifdef DEBUG