diff options
Diffstat (limited to 'pp_ctl.c')
| -rw-r--r-- | pp_ctl.c | 34 |
1 files changed, 34 insertions, 0 deletions
@@ -1645,6 +1645,40 @@ Perl_die_unwind(pTHX_ SV *msv) I32 cxix; I32 gimme; + /* + * Historically, perl used to set ERRSV ($@) early in the die + * process and rely on it not getting clobbered during unwinding. + * That sucked, because it was liable to get clobbered, so the + * setting of ERRSV used to emit the exception from eval{} has + * been moved to much later, after unwinding (see just before + * JMPENV_JUMP below). However, some modules were relying on the + * early setting, by examining $@ during unwinding to use it as + * a flag indicating whether the current unwinding was caused by + * an exception. It was never a reliable flag for that purpose, + * being totally open to false positives even without actual + * clobberage, but was useful enough for production code to + * semantically rely on it. + * + * We'd like to have a proper introspective interface that + * explicitly describes the reason for whatever unwinding + * operations are currently in progress, so that those modules + * work reliably and $@ isn't further overloaded. But we don't + * have one yet. In its absence, as a stopgap measure, ERRSV is + * now *additionally* set here, before unwinding, to serve as the + * (unreliable) flag that it used to. + * + * This behaviour is temporary, and should be removed when a + * proper way to detect exceptional unwinding has been developed. + * As of 2010-12, the authors of modules relying on the hack + * are aware of the issue, because the modules failed on + * perls 5.13.{1..7} which had late setting of $@ without this + * early-setting hack. + */ + if (!(in_eval & EVAL_KEEPERR)) { + SvTEMP_off(exceptsv); + sv_setsv(ERRSV, exceptsv); + } + while ((cxix = dopoptoeval(cxstack_ix)) < 0 && PL_curstackinfo->si_prev) { |