break;
}
- /*determine the radix point len, e.g. length(".") in "1.2" */
+ /* Determine the buffer size needed for the various
+ * floating-point formats.
+ *
+ * The basic possibilities are:
+ *
+ * <---P--->
+ * %f 1111111.123456789
+ * %e 1.111111123e+06
+ * %a 0x1.0f4471f9bp+20
+ * %g 1111111.12
+ * %g 1.11111112e+15
+ *
+ * where P is the value of the precision in the format, or 6
+ * if not specified. Note the two possible output formats of
+ * %g; in both cases the number of significant digits is <=
+ * precision.
+ *
+ * For most of the format types the maximum buffer size needed
+ * is precision, plus: any leading 1 or 0x1, the radix
+ * point, and an exponent. The difficult one is %f: for a
+ * large positive exponent it can have many leading digits,
+ * which needs to be calculated specially. Also %a is slightly
+ * different in that in the absence of a specified precision,
+ * it uses as many digits as necessary to distinguish
+ * different values.
+ *
+ * First, here are the constant bits. For ease of calculation
+ * we over-estimate the needed buffer size, for example by
+ * assuming all formats have an exponent and a leading 0x1.
+ */
+
+ float_need = 1 /* possible unary minus */
+ + 4 /* "0x1" plus very unlikely carry */
+ + 2 /* "e-", "p+" etc */
+ + 6 /* exponent: up to 16383 (quad fp) */
+ + 1; /* \0 */
+
+
+ /* determine the radix point len, e.g. length(".") in "1.2" */
radix_len = 1; /* assume '.' */
#ifdef USE_LOCALE_NUMERIC
/* note that we may either explicitly use PL_numeric_radix_sv
}
RESTORE_LC_NUMERIC();
#endif
- float_need = radix_len;
-
- /* frexp() (or frexpl) has some unspecified behaviour for
- * nan/inf/-inf, so lucky we've already handled them above */
- if (isALPHA_FOLD_NE(c, 'e')) {
+ /* this can't wrap unless PL_numeric_radix_sv is a string
+ * consuming virtually all the 32-bit or 64-bit address space
+ */
+ float_need += radix_len;
+
+ if (isALPHA_FOLD_EQ(c, 'f')) {
+ /* Determine how many digits before the radix point
+ * might be emitted. frexp() (or frexpl) has some
+ * unspecified behaviour for nan/inf/-inf, so lucky we've
+ * already handled them above */
+ STRLEN digits;
int i = PERL_INT_MIN;
(void)Perl_frexp((NV)fv, &i);
if (i == PERL_INT_MIN)
Perl_die(aTHX_ "panic: frexp: %" FV_GF, fv);
- hexfp = isALPHA_FOLD_EQ(c, 'a');
- if (UNLIKELY(hexfp)) {
- /* This seriously overshoots in most cases, but
- * better the undershooting. Firstly, all bytes
+
+ if (i > 0) {
+ digits = BIT_DIGITS(i);
+ if (float_need >= ((STRLEN)~0) - digits)
+ croak_memory_wrap();
+ float_need += digits;
+ }
+ }
+ else if (UNLIKELY(isALPHA_FOLD_EQ(c, 'a'))) {
+ hexfp = TRUE;
+ if (!has_precis) {
+ /* %a in the absence of precision may print as many
+ * digits as needed to represent the entire mantissa
+ * bit pattern.
+ * This estimate seriously overshoots in most cases,
+ * but better the undershooting. Firstly, all bytes
* of the NV are not mantissa, some of them are
* exponent. Secondly, for the reasonably common
* long doubles case, the "80-bit extended", two
- * or six bytes of the NV are unused. */
- float_need +=
- (fv < 0) ? 1 : 0 + /* possible unary minus */
- 2 + /* "0x" */
- 1 + /* the very unlikely carry */
- 1 + /* "1" */
- 1 + /* "." */
- 2 * NVSIZE + /* 2 hexdigits for each byte */
- 2 + /* "p+" */
- 6 + /* exponent: sign, plus up to 16383 (quad fp) */
- 1; /* \0 */
+ * or six bytes of the NV are unused. Also, we'll
+ * still pick up an extra +6 from the default
+ * precision calculation below. */
+ STRLEN digits =
#ifdef LONGDOUBLE_DOUBLEDOUBLE
- /* However, for the "double double", we need more.
- * Since each double has their own exponent, the
- * doubles may float (haha) rather far from each
- * other, and the number of required bits is much
- * larger, up to total of DOUBLEDOUBLE_MAXBITS bits.
- * See the definition of DOUBLEDOUBLE_MAXBITS.
- *
- * Need 2 hexdigits for each byte. */
- float_need += (DOUBLEDOUBLE_MAXBITS/8 + 1) * 2;
- /* the size for the exponent already added */
+ /* For the "double double", we need more.
+ * Since each double has their own exponent, the
+ * doubles may float (haha) rather far from each
+ * other, and the number of required bits is much
+ * larger, up to total of DOUBLEDOUBLE_MAXBITS bits.
+ * See the definition of DOUBLEDOUBLE_MAXBITS.
+ *
+ * Need 2 hexdigits for each byte. */
+ (DOUBLEDOUBLE_MAXBITS/8 + 1) * 2;
+#else
+ NVSIZE * 2; /* 2 hexdigits for each byte */
#endif
+ if (float_need >= ((STRLEN)~0) - digits)
+ croak_memory_wrap();
+ float_need += digits;
}
- else if (i > 0) {
- float_need = BIT_DIGITS(i);
- } /* if i < 0, the number of digits is hard to predict. */
}
{
#endif /* HAS_LDBL_SPRINTF_BUG */
- if (float_need >= ((STRLEN)~0) - 40)
+/* We should have correctly calculated (or indeed over-estimated) the
+ * buffer size, but you never know what strange floating-point systems
+ * there are out there. So for production use, add a little extra overhead.
+ * Under debugging don't, as it means we more more likely to quickly spot
+ * issues during development.
+ */
+#ifndef DEBUGGING
+ if (float_need >= ((STRLEN)~0) - 20)
croak_memory_wrap();
- float_need += 40; /* fudge factor */
+ float_need += 20; /* safety fudge factor */
+#endif
+
if (PL_efloatsize < float_need) {
Safefree(PL_efloatbuf);
PL_efloatsize = float_need;
https://perl5.git.perl.org / perl5.git / commitdiff