mirror of git://git.musl-libc.org/musl
fix integer overflows and uncaught EOVERFLOW in printf core
this patch fixes a large number of missed internal signed-overflow checks and errors in determining when the return value (output length) would exceed INT_MAX, which should result in EOVERFLOW. some of the issues fixed were reported by Alexander Cherepanov; others were found in subsequent review of the code. aside from the signed overflows being undefined behavior, the following specific bugs were found to exist in practice: - overflows computing length of floating point formats with huge explicit precisions, integer formats with prefix characters and huge explicit precisions, or string arguments or format strings longer than INT_MAX, resulted in wrong return value and wrong %n results. - literal width and precision values outside the range of int were misinterpreted, yielding wrong behavior in at least one well-defined case: string formats with precision greater than INT_MAX were sometimes truncated. - in cases where EOVERFLOW is produced, incorrect values could be written for %n specifiers past the point of exceeding INT_MAX. in addition to fixing these bugs, we now stop producing output immediately when output length would exceed INT_MAX, rather than continuing and returning an error only at the end.
This commit is contained in:
Rich Felker
parent
70d2687d85
commit
167dfe9672
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@ -272,6 +272,8 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
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if (s-buf==1 && (y||p>0||(fl&ALT_FORM))) *s++='.';
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} while (y);
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if (p > INT_MAX-2-(ebuf-estr)-pl)
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return -1;
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if (p && s-buf-2 < p)
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l = (p+2) + (ebuf-estr);
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else
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@ -383,17 +385,22 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
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p = MIN(p,MAX(0,9*(z-r-1)+e-j));
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}
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}
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if (p > INT_MAX-1-(p || (fl&ALT_FORM)))
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return -1;
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l = 1 + p + (p || (fl&ALT_FORM));
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if ((t|32)=='f') {
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if (e > INT_MAX-l) return -1;
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if (e>0) l+=e;
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} else {
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estr=fmt_u(e<0 ? -e : e, ebuf);
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while(ebuf-estr<2) *--estr='0';
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*--estr = (e<0 ? '-' : '+');
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*--estr = t;
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if (ebuf-estr > INT_MAX-l) return -1;
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l += ebuf-estr;
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}
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if (l > INT_MAX-pl) return -1;
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pad(f, ' ', w, pl+l, fl);
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out(f, prefix, pl);
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pad(f, '0', w, pl+l, fl^ZERO_PAD);
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@ -437,8 +444,10 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
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static int getint(char **s) {
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int i;
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for (i=0; isdigit(**s); (*s)++)
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i = 10*i + (**s-'0');
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for (i=0; isdigit(**s); (*s)++) {
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if (i > INT_MAX/10U || **s-'0' > INT_MAX-10*i) i = -1;
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else i = 10*i + (**s-'0');
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}
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return i;
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}
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@ -446,12 +455,12 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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{
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char *a, *z, *s=(char *)fmt;
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unsigned l10n=0, fl;
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int w, p;
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int w, p, xp;
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union arg arg;
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int argpos;
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unsigned st, ps;
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int cnt=0, l=0;
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int i;
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size_t i;
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char buf[sizeof(uintmax_t)*3+3+LDBL_MANT_DIG/4];
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const char *prefix;
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int t, pl;
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@ -459,18 +468,19 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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char mb[4];
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for (;;) {
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/* This error is only specified for snprintf, but since it's
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* unspecified for other forms, do the same. Stop immediately
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* on overflow; otherwise %n could produce wrong results. */
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if (l > INT_MAX - cnt) goto overflow;
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/* Update output count, end loop when fmt is exhausted */
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if (cnt >= 0) {
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if (l > INT_MAX - cnt) {
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errno = EOVERFLOW;
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cnt = -1;
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} else cnt += l;
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}
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cnt += l;
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if (!*s) break;
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/* Handle literal text and %% format specifiers */
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for (a=s; *s && *s!='%'; s++);
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for (z=s; s[0]=='%' && s[1]=='%'; z++, s+=2);
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if (z-a > INT_MAX-cnt) goto overflow;
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l = z-a;
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if (f) out(f, a, l);
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if (l) continue;
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@ -498,9 +508,9 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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} else if (!l10n) {
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w = f ? va_arg(*ap, int) : 0;
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s++;
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} else return -1;
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} else goto inval;
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if (w<0) fl|=LEFT_ADJ, w=-w;
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} else if ((w=getint(&s))<0) return -1;
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} else if ((w=getint(&s))<0) goto overflow;
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/* Read precision */
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if (*s=='.' && s[1]=='*') {
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@ -511,24 +521,29 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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} else if (!l10n) {
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p = f ? va_arg(*ap, int) : 0;
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s+=2;
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} else return -1;
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} else goto inval;
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xp = (p>=0);
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} else if (*s=='.') {
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s++;
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p = getint(&s);
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} else p = -1;
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xp = 1;
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} else {
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p = -1;
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xp = 0;
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}
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/* Format specifier state machine */
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st=0;
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do {
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if (OOB(*s)) return -1;
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if (OOB(*s)) goto inval;
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ps=st;
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st=states[st]S(*s++);
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} while (st-1<STOP);
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if (!st) return -1;
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if (!st) goto inval;
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/* Check validity of argument type (nl/normal) */
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if (st==NOARG) {
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if (argpos>=0) return -1;
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if (argpos>=0) goto inval;
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} else {
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if (argpos>=0) nl_type[argpos]=st, arg=nl_arg[argpos];
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else if (f) pop_arg(&arg, st, ap);
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@ -584,6 +599,7 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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case 'u':
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a = fmt_u(arg.i, z);
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}
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if (xp && p<0) goto overflow;
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if (p>=0) fl &= ~ZERO_PAD;
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if (!arg.i && !p) {
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a=z;
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@ -599,9 +615,9 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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if (1) a = strerror(errno); else
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case 's':
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a = arg.p ? arg.p : "(null)";
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z = memchr(a, 0, p);
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if (!z) z=a+p;
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else p=z-a;
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z = a + strnlen(a, p<0 ? INT_MAX : p);
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if (p<0 && *z) goto overflow;
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p = z-a;
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fl &= ~ZERO_PAD;
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break;
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case 'C':
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@ -611,8 +627,9 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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p = -1;
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case 'S':
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ws = arg.p;
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for (i=l=0; i<0U+p && *ws && (l=wctomb(mb, *ws++))>=0 && l<=0U+p-i; i+=l);
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for (i=l=0; i<p && *ws && (l=wctomb(mb, *ws++))>=0 && l<=p-i; i+=l);
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if (l<0) return -1;
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if (i > INT_MAX) goto overflow;
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p = i;
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pad(f, ' ', w, p, fl);
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ws = arg.p;
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@ -623,12 +640,16 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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continue;
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case 'e': case 'f': case 'g': case 'a':
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case 'E': case 'F': case 'G': case 'A':
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if (xp && p<0) goto overflow;
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l = fmt_fp(f, arg.f, w, p, fl, t);
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if (l<0) goto overflow;
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continue;
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}
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if (p < z-a) p = z-a;
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if (p > INT_MAX-pl) goto overflow;
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if (w < pl+p) w = pl+p;
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if (w > INT_MAX-cnt) goto overflow;
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pad(f, ' ', w, pl+p, fl);
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out(f, prefix, pl);
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@ -646,8 +667,15 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
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for (i=1; i<=NL_ARGMAX && nl_type[i]; i++)
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pop_arg(nl_arg+i, nl_type[i], ap);
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for (; i<=NL_ARGMAX && !nl_type[i]; i++);
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if (i<=NL_ARGMAX) return -1;
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if (i<=NL_ARGMAX) goto inval;
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return 1;
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inval:
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errno = EINVAL;
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return -1;
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overflow:
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errno = EOVERFLOW;
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return -1;
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}
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int vfprintf(FILE *restrict f, const char *restrict fmt, va_list ap)
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@ -154,8 +154,10 @@ static void out(FILE *f, const wchar_t *s, size_t l)
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static int getint(wchar_t **s) {
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int i;
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for (i=0; iswdigit(**s); (*s)++)
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i = 10*i + (**s-'0');
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for (i=0; iswdigit(**s); (*s)++) {
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if (i > INT_MAX/10U || **s-'0' > INT_MAX-10*i) i = -1;
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else i = 10*i + (**s-'0');
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}
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return i;
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}
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@ -168,8 +170,8 @@ static const char sizeprefix['y'-'a'] = {
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static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_arg, int *nl_type)
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{
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wchar_t *a, *z, *s=(wchar_t *)fmt;
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unsigned l10n=0, litpct, fl;
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int w, p;
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unsigned l10n=0, fl;
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int w, p, xp;
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union arg arg;
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int argpos;
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unsigned st, ps;
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@ -181,20 +183,19 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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wchar_t wc;
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for (;;) {
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/* This error is only specified for snprintf, but since it's
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* unspecified for other forms, do the same. Stop immediately
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* on overflow; otherwise %n could produce wrong results. */
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if (l > INT_MAX - cnt) goto overflow;
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/* Update output count, end loop when fmt is exhausted */
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if (cnt >= 0) {
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if (l > INT_MAX - cnt) {
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if (!ferror(f)) errno = EOVERFLOW;
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cnt = -1;
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} else cnt += l;
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}
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cnt += l;
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if (!*s) break;
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/* Handle literal text and %% format specifiers */
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for (a=s; *s && *s!='%'; s++);
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litpct = wcsspn(s, L"%")/2; /* Optimize %%%% runs */
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z = s+litpct;
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s += 2*litpct;
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for (z=s; s[0]=='%' && s[1]=='%'; z++, s+=2);
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if (z-a > INT_MAX-cnt) goto overflow;
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l = z-a;
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if (f) out(f, a, l);
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if (l) continue;
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@ -222,9 +223,9 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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} else if (!l10n) {
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w = f ? va_arg(*ap, int) : 0;
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s++;
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} else return -1;
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} else goto inval;
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if (w<0) fl|=LEFT_ADJ, w=-w;
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} else if ((w=getint(&s))<0) return -1;
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} else if ((w=getint(&s))<0) goto overflow;
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/* Read precision */
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if (*s=='.' && s[1]=='*') {
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@ -235,24 +236,29 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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} else if (!l10n) {
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p = f ? va_arg(*ap, int) : 0;
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s+=2;
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} else return -1;
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} else goto inval;
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xp = (p>=0);
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} else if (*s=='.') {
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s++;
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p = getint(&s);
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} else p = -1;
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xp = 1;
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} else {
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p = -1;
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xp = 0;
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}
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/* Format specifier state machine */
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st=0;
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do {
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if (OOB(*s)) return -1;
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if (OOB(*s)) goto inval;
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ps=st;
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st=states[st]S(*s++);
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} while (st-1<STOP);
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if (!st) return -1;
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if (!st) goto inval;
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/* Check validity of argument type (nl/normal) */
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if (st==NOARG) {
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if (argpos>=0) return -1;
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if (argpos>=0) goto inval;
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} else {
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if (argpos>=0) nl_type[argpos]=st, arg=nl_arg[argpos];
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else if (f) pop_arg(&arg, st, ap);
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@ -285,8 +291,9 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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continue;
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case 'S':
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a = arg.p;
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z = wmemchr(a, 0, p);
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if (z) p=z-a;
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z = a + wcsnlen(a, p<0 ? INT_MAX : p);
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if (p<0 && *z) goto overflow;
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p = z-a;
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if (w<p) w=p;
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if (!(fl&LEFT_ADJ)) fprintf(f, "%*s", w-p, "");
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out(f, a, p);
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@ -298,9 +305,9 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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case 's':
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if (!arg.p) arg.p = "(null)";
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bs = arg.p;
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if (p<0) p = INT_MAX;
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for (i=l=0; l<p && (i=mbtowc(&wc, bs, MB_LEN_MAX))>0; bs+=i, l++);
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for (i=l=0; l<(p<0?INT_MAX:p) && (i=mbtowc(&wc, bs, MB_LEN_MAX))>0; bs+=i, l++);
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if (i<0) return -1;
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if (p<0 && *bs) goto overflow;
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p=l;
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if (w<p) w=p;
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if (!(fl&LEFT_ADJ)) fprintf(f, "%*s", w-p, "");
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@ -315,6 +322,7 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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continue;
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}
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if (xp && p<0) goto overflow;
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snprintf(charfmt, sizeof charfmt, "%%%s%s%s%s%s*.*%c%c",
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"#"+!(fl & ALT_FORM),
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"+"+!(fl & MARK_POS),
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@ -341,6 +349,13 @@ static int wprintf_core(FILE *f, const wchar_t *fmt, va_list *ap, union arg *nl_
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for (; i<=NL_ARGMAX && !nl_type[i]; i++);
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if (i<=NL_ARGMAX) return -1;
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return 1;
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inval:
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errno = EINVAL;
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return -1;
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overflow:
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errno = EOVERFLOW;
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return -1;
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}
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int vfwprintf(FILE *restrict f, const wchar_t *restrict fmt, va_list ap)
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