implement scanf("%2$i", &int1, &int2)
Jeff Johnston
jjohnstn@redhat.com
Wed May 23 20:33:00 GMT 2007
Eric Blake wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> OK to apply? I used printf as a model, but positional args in scanf
> turned out to be a lot easier than positional arguments in printf :)
>
>
Ok to apply.
> Also, I noticed that printf (and thus my scanf patch) goes to great
> lengths to ensure it does not overflow the internal array of MAX_POS_ARGS
> stored arguments, as well as trying to support mixed positional and
> non-positional arguments; however, POSIX is clear that behavior is
> undefined if positional and non-positional arguments are mixed in the same
> format string, or if more than NL_ARGMAX indices are requested. Is it
> worth trying to simplify the code here by allowing array overflow on
> non-compliant format strings, rather than trying to be accommodating?
>
>
I don't see a real point. The platforms that really care about the
space will likely not enable positional args.
Thanks for doing this.
-- Jeff J.
> 2007-05-21 Eric Blake <ebb9@byu.net>
>
> * libc/stdio/vfscanf.c (__SVFSCANF_R): Support scanf(%1$s).
> Avoid warning when !FLOATING_POINT.
> * libc/stdio/vfprintf.c (_VFPRINTF_R): Simplify _NO_POS_ARGS
> slightly.
>
> - --
> Don't work too hard, make some time for fun as well!
>
> Eric Blake ebb9@byu.net
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> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
>
> iD8DBQFGUZW+84KuGfSFAYARAtz/AJ4oN5pKXJYeKvidIzcmHECfq5wcnACcD+D8
> xNL/2XMaNg7H0gDzPFDKBcI=
> =Hda6
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>
> ------------------------------------------------------------------------
>
> Index: libc/stdio/vfprintf.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdio/vfprintf.c,v
> retrieving revision 1.60
> diff -u -p -r1.60 vfprintf.c
> --- libc/stdio/vfprintf.c 18 May 2007 14:33:30 -0000 1.60
> +++ libc/stdio/vfprintf.c 21 May 2007 12:39:02 -0000
> @@ -125,8 +125,8 @@ static char *rcsid = "$Id: vfprintf.c,v
> # endif
> #endif
>
> -#define _NO_POS_ARGS
> -#if defined _WANT_IO_POS_ARGS
> +#define _NO_POS_ARGS
> +#ifdef _WANT_IO_POS_ARGS
> # undef _NO_POS_ARGS
> #endif
>
> @@ -385,9 +385,9 @@ _DEFUN(_VFPRINTF_R, (data, fp, fmt0, ap)
> register struct __siov *iovp;/* for PRINT macro */
> register int flags; /* flags as above */
> char *fmt_anchor; /* current format spec being processed */
> +#ifndef _NO_POS_ARGS
> int N; /* arg number */
> int arg_index; /* index into args processed directly */
> -#ifndef _NO_POS_ARGS
> int numargs; /* number of varargs read */
> char *saved_fmt; /* saved fmt pointer */
> union arg_val args[MAX_POS_ARGS];
> @@ -538,8 +538,8 @@ _DEFUN(_VFPRINTF_R, (data, fp, fmt0, ap)
> uio.uio_resid = 0;
> uio.uio_iovcnt = 0;
> ret = 0;
> - arg_index = 0;
> #ifndef _NO_POS_ARGS
> + arg_index = 0;
> saved_fmt = NULL;
> arg_type[0] = -1;
> numargs = 0;
> @@ -580,8 +580,8 @@ _DEFUN(_VFPRINTF_R, (data, fp, fmt0, ap)
> width = 0;
> prec = -1;
> sign = '\0';
> - N = arg_index;
> #ifndef _NO_POS_ARGS
> + N = arg_index;
> is_pos_arg = 0;
> #endif
>
> @@ -609,9 +609,9 @@ reswitch: switch (ch) {
> flags |= ALT;
> goto rflag;
> case '*':
> - n = N;
> #ifndef _NO_POS_ARGS
> /* we must check for positional arg used for dynamic width */
> + n = N;
> old_is_pos_arg = is_pos_arg;
> is_pos_arg = 0;
> if (is_digit (*fmt)) {
> @@ -661,9 +661,9 @@ reswitch: switch (ch) {
> goto rflag;
> case '.':
> if ((ch = *fmt++) == '*') {
> - n = N;
> #ifndef _NO_POS_ARGS
> /* we must check for positional arg used for dynamic width */
> + n = N;
> old_is_pos_arg = is_pos_arg;
> is_pos_arg = 0;
> if (is_digit (*fmt)) {
> Index: libc/stdio/vfscanf.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdio/vfscanf.c,v
> retrieving revision 1.36
> diff -u -p -r1.36 vfscanf.c
> --- libc/stdio/vfscanf.c 18 May 2007 14:33:30 -0000 1.36
> +++ libc/stdio/vfscanf.c 21 May 2007 12:39:03 -0000
> @@ -113,11 +113,8 @@ Supporting OS subroutines required:
> #include <limits.h>
> #include <wchar.h>
> #include <string.h>
> -#ifdef _HAVE_STDC
> #include <stdarg.h>
> -#else
> -#include <varargs.h>
> -#endif
> +#include <errno.h>
> #include "local.h"
>
> #ifdef INTEGER_ONLY
> @@ -169,6 +166,18 @@ extern _LONG_DOUBLE _strtold _PARAMS((ch
> # undef _NO_LONGLONG
> #endif
>
> +#define _NO_POS_ARGS
> +#ifdef _WANT_IO_POS_ARGS
> +# undef _NO_POS_ARGS
> +# ifdef NL_ARGMAX
> +# define MAX_POS_ARGS NL_ARGMAX
> +# else
> +# define MAX_POS_ARGS 32
> +# endif
> +
> +static void * get_arg (int, va_list *, int *, void **);
> +#endif /* _WANT_IO_POS_ARGS */
> +
> /*
> * Flags used during conversion.
> */
> @@ -276,6 +285,13 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> register char *p0; /* saves original value of p when necessary */
> int nassigned; /* number of fields assigned */
> int nread; /* number of characters consumed from fp */
> +#ifndef _NO_POS_ARGS
> + int N; /* arg number */
> + int arg_index = 0; /* index into args processed directly */
> + int numargs = 0; /* number of varargs read */
> + void *args[MAX_POS_ARGS]; /* positional args read */
> + int is_pos_arg; /* is current format positional? */
> +#endif
> int base = 0; /* base argument to strtol/strtoul */
> int nbytes = 1; /* number of bytes read from fmt string */
> wchar_t wc; /* wchar to use to read format string */
> @@ -291,9 +307,11 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> char *cp;
> short *sp;
> int *ip;
> +#ifdef FLOATING_POINT
> float *flp;
> _LONG_DOUBLE *ldp;
> double *dp;
> +#endif
> long *lp;
> #ifndef _NO_LONGLONG
> long long *llp;
> @@ -303,6 +321,22 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> static _CONST short basefix[17] =
> {10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16};
>
> + /* Macro to support positional arguments */
> +#ifndef _NO_POS_ARGS
> +# define GET_ARG(n, ap, type) \
> + ((type) (is_pos_arg \
> + ? (n < numargs \
> + ? args[n] \
> + : get_arg (n, &ap, &numargs, args)) \
> + : (arg_index++ < numargs \
> + ? args[n] \
> + : (numargs < MAX_POS_ARGS \
> + ? args[numargs++] = va_arg (ap, void *) \
> + : va_arg (ap, void *)))))
> +#else
> +# define GET_ARG(n, ap, type) (va_arg (ap, type))
> +#endif
> +
> _flockfile (fp);
>
> nassigned = 0;
> @@ -332,6 +366,10 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> goto literal;
> width = 0;
> flags = 0;
> +#ifndef _NO_POS_ARGS
> + N = arg_index;
> + is_pos_arg = 0;
> +#endif
>
> /*
> * switch on the format. continue if done; break once format
> @@ -439,6 +477,19 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> width = width * 10 + c - '0';
> goto again;
>
> +#ifndef _NO_POS_ARGS
> + case '$':
> + if (width <= MAX_POS_ARGS)
> + {
> + N = width - 1;
> + is_pos_arg = 1;
> + width = 0;
> + goto again;
> + }
> + rptr->_errno = EINVAL;
> + goto input_failure;
> +#endif /* !_NO_POS_ARGS */
> +
> /*
> * Conversions. Those marked `compat' are for
> * 4.[123]BSD compatibility.
> @@ -540,31 +591,31 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> #ifdef _WANT_IO_C99_FORMATS
> if (flags & CHAR)
> {
> - cp = va_arg (ap, char *);
> + cp = GET_ARG (N, ap, char *);
> *cp = nread;
> }
> else
> #endif
> if (flags & SHORT)
> {
> - sp = va_arg (ap, short *);
> + sp = GET_ARG (N, ap, short *);
> *sp = nread;
> }
> else if (flags & LONG)
> {
> - lp = va_arg (ap, long *);
> + lp = GET_ARG (N, ap, long *);
> *lp = nread;
> }
> #ifndef _NO_LONGLONG
> else if (flags & LONGDBL)
> {
> - llp = va_arg (ap, long long*);
> + llp = GET_ARG (N, ap, long long*);
> *llp = nread;
> }
> #endif
> else
> {
> - ip = va_arg (ap, int *);
> + ip = GET_ARG (N, ap, int *);
> *ip = nread;
> }
> continue;
> @@ -626,7 +677,7 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> if (flags & LONG)
> {
> if ((flags & SUPPRESS) == 0)
> - wcp = va_arg (ap, wchar_t *);
> + wcp = GET_ARG (N, ap, wchar_t *);
> else
> wcp = NULL;
> n = 0;
> @@ -690,7 +741,7 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> }
> else
> {
> - size_t r = fread ((_PTR) va_arg (ap, char *), 1, width, fp);
> + size_t r = fread ((_PTR) GET_ARG (N, ap, char *), 1, width, fp);
>
> if (r == 0)
> goto input_failure;
> @@ -724,7 +775,7 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> }
> else
> {
> - p0 = p = va_arg (ap, char *);
> + p0 = p = GET_ARG (N, ap, char *);
> while (ccltab[*fp->_p])
> {
> fp->_r--;
> @@ -755,7 +806,7 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> {
> /* Process %S and %ls placeholders */
> if ((flags & SUPPRESS) == 0)
> - wcp = va_arg (ap, wchar_t *);
> + wcp = GET_ARG (N, ap, wchar_t *);
> else
> wcp = &wc;
> n = 0;
> @@ -814,7 +865,7 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> }
> else
> {
> - p0 = p = va_arg (ap, char *);
> + p0 = p = GET_ARG (N, ap, char *);
> while (!isspace (*fp->_p))
> {
> fp->_r--;
> @@ -993,22 +1044,22 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> *p = 0;
> res = (*ccfn) (rptr, buf, (char **) NULL, base);
> if (flags & POINTER)
> - *(va_arg (ap, _PTR *)) = (_PTR) (unsigned _POINTER_INT) res;
> + *(GET_ARG (N, ap, _PTR *)) = (_PTR) (unsigned _POINTER_INT) res;
> #ifdef _WANT_IO_C99_FORMATS
> else if (flags & CHAR)
> {
> - cp = va_arg (ap, char *);
> + cp = GET_ARG (N, ap, char *);
> *cp = res;
> }
> #endif
> else if (flags & SHORT)
> {
> - sp = va_arg (ap, short *);
> + sp = GET_ARG (N, ap, short *);
> *sp = res;
> }
> else if (flags & LONG)
> {
> - lp = va_arg (ap, long *);
> + lp = GET_ARG (N, ap, long *);
> *lp = res;
> }
> #ifndef _NO_LONGLONG
> @@ -1019,13 +1070,13 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
> resll = _strtoull_r (rptr, buf, (char **) NULL, base);
> else
> resll = _strtoll_r (rptr, buf, (char **) NULL, base);
> - llp = va_arg (ap, long long*);
> + llp = GET_ARG (N, ap, long long*);
> *llp = resll;
> }
> #endif
> else
> {
> - ip = va_arg (ap, int *);
> + ip = GET_ARG (N, ap, int *);
> *ip = res;
> }
> nassigned++;
> @@ -1257,17 +1308,17 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap
>
> if (flags & LONG)
> {
> - dp = va_arg (ap, double *);
> + dp = GET_ARG (N, ap, double *);
> *dp = res;
> }
> else if (flags & LONGDBL)
> {
> - ldp = va_arg (ap, _LONG_DOUBLE *);
> + ldp = GET_ARG (N, ap, _LONG_DOUBLE *);
> *ldp = QUAD_RES;
> }
> else
> {
> - flp = va_arg (ap, float *);
> + flp = GET_ARG (N, ap, float *);
> if (isnan (res))
> *flp = nanf (NULL);
> else
> @@ -1288,3 +1339,18 @@ all_done:
> _funlockfile (fp);
> return nassigned;
> }
> +
> +#ifndef _NO_POS_ARGS
> +/* Process all intermediate arguments. Fortunately, with scanf, all
> + intermediate arguments are sizeof(void*), so we don't need to scan
> + ahead. */
> +static void *
> +get_arg (int n, va_list *ap, int *numargs_p, void **args)
> +{
> + int numargs = *numargs_p;
> + while (n >= numargs)
> + args[numargs++] = va_arg (*ap, void *);
> + *numargs_p = numargs;
> + return args[n];
> +}
> +#endif /* !_NO_POS_ARGS */
>
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