diff options
Diffstat (limited to 'sv.c')
| -rw-r--r-- | sv.c | 47 |
1 files changed, 10 insertions, 37 deletions
@@ -1165,42 +1165,9 @@ Perl_sv_upgrade(pTHX_ register SV *const sv, svtype new_type) old_body = SvANY(sv); /* Copying structures onto other structures that have been neatly zeroed - has a subtle gotcha. Consider XPVMG - - +------+------+------+------+------+-------+-------+ - | NV | CUR | LEN | IV | MAGIC | STASH | - +------+------+------+------+------+-------+-------+ - 0 4 8 12 16 20 24 28 - - where NVs are aligned to 8 bytes, so that sizeof that structure is - actually 32 bytes long, with 4 bytes of padding at the end: - - +------+------+------+------+------+-------+-------+------+ - | NV | CUR | LEN | IV | MAGIC | STASH | ??? | - +------+------+------+------+------+-------+-------+------+ - 0 4 8 12 16 20 24 28 32 - - so what happens if you allocate memory for this structure: - - +------+------+------+------+------+-------+-------+------+------+... - | NV | CUR | LEN | IV | MAGIC | STASH | GP | NAME | - +------+------+------+------+------+-------+-------+------+------+... - 0 4 8 12 16 20 24 28 32 36 - - zero it, then copy sizeof(XPVMG) bytes on top of it? Not quite what you - expect, because you copy the area marked ??? onto GP. Now, ??? may have - started out as zero once, but it's quite possible that it isn't. So now, - rather than a nicely zeroed GP, you have it pointing somewhere random. - Bugs ensue. - - (In fact, GP ends up pointing at a previous GP structure, because the - principle cause of the padding in XPVMG getting garbage is a copy of - sizeof(XPVMG) bytes from a XPVGV structure in sv_unglob. Right now - this happens to be moot because XPVGV has been re-ordered, with GP - no longer after STASH) - - So we are careful and work out the size of used parts of all the - structures. */ + has a subtle gotcha. The original structure may have unused padding + at the end, which the new structure assigns a meaning to. So we are + careful and work out the size of used parts of all the structures. */ switch (old_type) { case SVt_NULL: @@ -2716,6 +2683,7 @@ Perl_sv_2pv_flags(pTHX_ register SV *const sv, STRLEN *const lp, const I32 flags { dVAR; register char *s; + bool priv = FALSE; if (!sv) { if (lp) @@ -2923,6 +2891,7 @@ Perl_sv_2pv_flags(pTHX_ register SV *const sv, STRLEN *const lp, const I32 flags Move(ptr, s, len, char); s += len; *s = '\0'; + priv = TRUE; } else if (SvNOKp(sv)) { if (SvTYPE(sv) < SVt_PVNV) @@ -2944,6 +2913,7 @@ Perl_sv_2pv_flags(pTHX_ register SV *const sv, STRLEN *const lp, const I32 flags if (s[-1] == '.') *--s = '\0'; #endif + priv = TRUE; } else { if (isGV_with_GP(sv)) { @@ -2987,7 +2957,10 @@ Perl_sv_2pv_flags(pTHX_ register SV *const sv, STRLEN *const lp, const I32 flags *lp = len; SvCUR_set(sv, len); } - SvPOK_on(sv); + if (priv) + SvPOKp_on(sv); + else + SvPOK_on(sv); DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%"UVxf" 2pv(%s)\n", PTR2UV(sv),SvPVX_const(sv))); if (flags & SV_CONST_RETURN) |