Carp: Avoid run-time mods; StrVal workarounds

Carp needs to avoid loading modules while reporting errors, because
it may be invoked via $SIG{__DIE__} after a syntax error, when BEGIN
blocks are forbidden.

Before this commit (as of v5.27.8-360-gc99363a) it was doing just that
for reference arguments within stack traces.

That means we either need to load overload.pm at start-up so that
overload::StrVal is already available, or avoid overload::StrVal
altogether.

It turns out that various versions of overload::StrVal have
their own problems that prevent Carp from using them (out-
lined in the comments added to Carp.pm and also described at
<https://rt.perl.org/Ticket/Display.html?id=132902#txn-1535564>).

So we now follow two approaches:  If overloading.pm is available, use
that; otherwise, use a hideous workaround inspired by ancient imple-
entations of overload::StrVal and Scalar::Util::blessed, while avoid-
ing the bugs in those old versions.

1 files changed, 1 insertions, 0 deletions

diff --git a/MANIFEST b/MANIFEST
index acc1bcba7f..b054110b65 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -2975,6 +2975,7 @@ dist/Carp/t/errno.t		See if Carp preserves $! and $^E
 dist/Carp/t/heavy.t		See if Carp::Heavy works
 dist/Carp/t/heavy_mismatch.t		See if Carp::Heavy catches version mismatch
 dist/Carp/t/rt52610_crash.t		Test that we can gracefully handle serializing the stack with stack-refcounting bugs
+dist/Carp/t/stack_after_err.t	Test stack traces after syntax errors
 dist/Carp/t/stash_deletion.t		See if Carp handles stash deletion
 dist/Carp/t/swash.t		See if Carp avoids breaking swash loading
 dist/Carp/t/vivify_gv.t		See if Carp leaves utf8:: stuff alone