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Re: lib/57250: dtoa mishandles infinite doubles on 32bit big endian machines
The following reply was made to PR lib/57250; it has been noted by GNATS.
From: Havard Eidnes <he%NetBSD.org@localhost>
To: gnats-bugs%netbsd.org@localhost, martin%duskware.de@localhost
Cc: lib-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
netbsd-bugs%netbsd.org@localhost, martin%NetBSD.org@localhost
Subject: Re: lib/57250: dtoa mishandles infinite doubles on 32bit big
endian machines
Date: Tue, 04 Apr 2023 20:49:25 +0200 (CEST)
...and after Christos massaged the code to do more code sharing
(and delete some now-un-needed code), and fixing the
non-WIDE_DOUBLE build issues, this is the resulting diff.
- Havard
------------------------------
Index: include/extern.h
===================================================================
RCS file: /cvsroot/src/lib/libc/include/extern.h,v
retrieving revision 1.26
diff -u -p -r1.26 extern.h
--- include/extern.h 15 May 2020 14:37:21 -0000 1.26
+++ include/extern.h 4 Apr 2023 18:44:22 -0000
@@ -49,11 +49,17 @@ struct sigaction;
int __sigaction_sigtramp(int, const struct sigaction *,
struct sigaction *, const void *, int);
+/* is "long double" and "double" different? */
+#if (__LDBL_MANT_DIG__ != __DBL_MANT_DIG__) || \
+ (__LDBL_MAX_EXP__ != __DBL_MAX_EXP__)
+#define WIDE_DOUBLE
+#endif
+
#ifdef WIDE_DOUBLE
-char *__hdtoa(double, const char *, int, int *, int *, char **);
char *__hldtoa(long double, const char *, int, int *, int *, char **);
char *__ldtoa(long double *, int, int, int *, int *, char **);
#endif
+char *__hdtoa(double, const char *, int, int *, int *, char **);
#ifndef __LIBC12_SOURCE__
struct syslog_data;
Index: stdio/Makefile.inc
===================================================================
RCS file: /cvsroot/src/lib/libc/stdio/Makefile.inc,v
retrieving revision 1.47
diff -u -p -r1.47 Makefile.inc
--- stdio/Makefile.inc 29 Dec 2015 17:55:23 -0000 1.47
+++ stdio/Makefile.inc 4 Apr 2023 18:44:22 -0000
@@ -4,8 +4,6 @@
# stdio sources
.PATH: ${.CURDIR}/stdio
-CPPFLAGS+=-DWIDE_DOUBLE
-
SRCS+= clrerr.c dprintf.c fclose.c fdopen.c feof.c ferror.c \
fflush.c fgetc.c fgetln.c fgetpos.c fgets.c fgetstr.c fgetwc.c \
fgetwln.c fgetws.c fileno.c findfp.c flags.c flockfile.c fopen.c \
Index: stdio/vfwprintf.c
===================================================================
RCS file: /cvsroot/src/lib/libc/stdio/vfwprintf.c,v
retrieving revision 1.39
diff -u -p -r1.39 vfwprintf.c
--- stdio/vfwprintf.c 19 Apr 2022 20:32:16 -0000 1.39
+++ stdio/vfwprintf.c 4 Apr 2023 18:44:22 -0000
@@ -581,9 +581,6 @@ WDECL(vf,printf_l)(FILE * __restrict fp,
#define DEFPREC 6
static int exponent(CHAR_T *, int, int);
-#ifndef WIDE_DOUBLE
-static char *cvt(double, int, int, char *, int *, int, int *);
-#endif
#endif /* !NO_FLOATING_POINT */
@@ -650,16 +647,15 @@ WDECL(__vf,printf_unlocked_l)(FILE *fp,
*/
char *decimal_point; /* locale specific decimal point */
#ifdef WIDE_DOUBLE
- int signflag; /* true if float is negative */
union { /* floating point arguments %[aAeEfFgG] */
double dbl;
long double ldbl;
} fparg;
- char *dtoaend; /* pointer to end of converted digits */
#else
double _double; /* double precision arguments %[eEfgG] */
- char softsign; /* temporary negative sign for floats */
#endif
+ int signflag; /* true if float is negative */
+ char *dtoaend; /* pointer to end of converted digits */
char *dtoaresult; /* buffer allocated by dtoa */
int expt; /* integer value of exponent */
char expchar; /* exponent character: [eEpP\0] */
@@ -1058,7 +1054,6 @@ reswitch: switch (ch) {
base = 10;
goto number;
#ifndef NO_FLOATING_POINT
-#ifdef WIDE_DOUBLE
case 'a':
case 'A':
if (ch == 'a') {
@@ -1072,6 +1067,7 @@ reswitch: switch (ch) {
}
if (prec >= 0)
prec++;
+#ifdef WIDE_DOUBLE
if (flags & LONGDBL) {
fparg.ldbl = GETARG(long double);
dtoaresult =
@@ -1083,6 +1079,12 @@ reswitch: switch (ch) {
__hdtoa(fparg.dbl, xdigs, prec,
&expt, &signflag, &dtoaend);
}
+#else
+ _double = GETARG(double);
+ dtoaresult =
+ __hdtoa(_double, xdigs, prec,
+ &expt, &signflag, &dtoaend);
+#endif /* WIDE_DOUBLE */
if (dtoaresult == NULL)
goto oomem;
@@ -1127,6 +1129,7 @@ reswitch: switch (ch) {
fp_begin:
if (prec < 0)
prec = DEFPREC;
+#ifdef WIDE_DOUBLE
if (flags & LONGDBL) {
fparg.ldbl = GETARG(long double);
dtoaresult =
@@ -1140,6 +1143,14 @@ fp_begin:
if (expt == 9999)
expt = INT_MAX;
}
+#else
+ _double = GETARG(double);
+ dtoaresult =
+ __dtoa(_double, expchar ? 2 : 3, prec,
+ &expt, &signflag, &dtoaend);
+ if (expt == 9999)
+ expt = INT_MAX;
+#endif /* WIDE_DOUBLE */
if (dtoaresult == NULL)
goto oomem;
_DIAGASSERT(__type_fit(int, dtoaend - dtoaresult));
@@ -1170,67 +1181,8 @@ fp_common:
flags &= ~ZEROPAD;
break;
}
-#else
- case 'e':
- case 'E':
- case 'f':
- case 'F':
- case 'g':
- case 'G':
- if (prec == -1) {
- prec = DEFPREC;
- } else if ((ch == 'g' || ch == 'G') && prec == 0) {
- prec = 1;
- }
-
- if (flags & LONGDBL) {
- _double = (double) GETARG(long double);
- } else {
- _double = GETARG(double);
- }
-
- /* do this before tricky precision changes */
- if (isinf(_double)) {
- if (_double < 0)
- sign = '-';
- if (ch == 'E' || ch == 'F' || ch == 'G')
- result = STRCONST("INF");
- else
- result = STRCONST("inf");
- size = 3;
- flags &= ~ZEROPAD;
- break;
- }
- if (isnan(_double)) {
- if (ch == 'E' || ch == 'F' || ch == 'G')
- result = STRCONST("NAN");
- else
- result = STRCONST("nan");
- size = 3;
- flags &= ~ZEROPAD;
- break;
- }
flags |= FPT;
- dtoaresult = cvt(_double, prec, flags, &softsign,
- &expt, ch, &ndig);
- if (dtoaresult == NULL)
- goto oomem;
- if (convbuf != NULL)
- free(convbuf);
-#ifndef NARROW
- result = convbuf = __mbsconv(dtoaresult, -1, loc);
-#else
- /*XXX inefficient*/
- result = convbuf = strdup(dtoaresult);
-#endif
- if (result == NULL)
- goto oomem;
- __freedtoa(dtoaresult);
- if (softsign)
- sign = '-';
-#endif
- flags |= FPT;
if (ch == 'g' || ch == 'G') {
if (expt > -4 && expt <= prec) {
/* Make %[gG] smell like %[fF] */
@@ -2001,57 +1953,7 @@ __grow_type_table (size_t nextarg, enum
return 0;
}
-
#ifndef NO_FLOATING_POINT
-#ifndef WIDE_DOUBLE
-static char *
-cvt(double value, int ndigits, int flags, char *sign, int *decpt, int ch,
- int *length)
-{
- int mode, dsgn;
- char *digits, *bp, *rve;
-
- _DIAGASSERT(decpt != NULL);
- _DIAGASSERT(length != NULL);
- _DIAGASSERT(sign != NULL);
-
- if (ch == 'f') {
- mode = 3; /* ndigits after the decimal point */
- } else {
- /* To obtain ndigits after the decimal point for the 'e'
- * and 'E' formats, round to ndigits + 1 significant
- * figures.
- */
- if (ch == 'e' || ch == 'E') {
- ndigits++;
- }
- mode = 2; /* ndigits significant digits */
- }
-
- digits = __dtoa(value, mode, ndigits, decpt, &dsgn, &rve);
- if (digits == NULL)
- return NULL;
- if (dsgn) {
- value = -value;
- *sign = '-';
- } else
- *sign = '\000';
- if ((ch != 'g' && ch != 'G') || flags & ALT) { /* Print trailing zeros */
- bp = digits + ndigits;
- if (ch == 'f') {
- if (*digits == '0' && value)
- *decpt = -ndigits + 1;
- bp += *decpt;
- }
- if (value == 0) /* kludge for __dtoa irregularity */
- rve = bp;
- while (rve < bp)
- *rve++ = '0';
- }
- *length = rve - digits;
- return digits;
-}
-#endif
static int
exponent(CHAR_T *p0, int expo, int fmtch)
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