Fix diagnostic.pm’s backtraces

Currently a user-defined error message is printed out like this:

-----
Uncaught exception from user code:
	panick:  at -e line 1.
 at -e line 1
	main::baz() called at -e line 1
	main::bar() called at -e line 1
	main::foo() called at -e line 1
-----

Errors generated from perl itself are printed like this:

-----
panic:  at -e line 1 (#1)
    (P) An internal error.

Uncaught exception from user code:
	panic:  at -e line 1.
 at -e line 1
	main::baz() called at -e line 1
	main::bar() called at -e line 1
	main::foo() called at -e line 1
-----

By using Carp::confess(), we end up with a screwy backtrace.  Some-
times it just ends up repeating the error and line number:

-----
panic:  at -e line 1 (#1)
    (P) An internal error.

Uncaught exception from user code:
	panic:  at -e line 1.
 at -e line 1
-----
Uncaught exception from user code:
	panick at -e line 1.
 at -e line 1
-----

This commit cleans these up to print like this:

-----
Uncaught exception from user code:
	panick:  at -e line 1.
	main::baz() called at -e line 1
	main::bar() called at -e line 1
	main::foo() called at -e line 1
-----
panic:  at -e line 1 (#1)
    (P) An internal error.

Uncaught exception from user code:
	panic:  at -e line 1.
	main::baz() called at -e line 1
	main::bar() called at -e line 1
	main::foo() called at -e line 1
-----
panic:  at -e line 1 (#1)
    (P) An internal error.

Uncaught exception from user code:
	panic:  at -e line 1.
-----
Uncaught exception from user code:
	panick at -e line 1.
-----

You might ask:  Why not remove the ‘uncaught exception’ message alto-
gether after an error description.  It’s because the error description
is a diagnostic, which only prints once for each error or warning
encountered.  So you could have eval { die } somewhere else in the
code, which causes a description to be printed.  And later you have a
die() that exits the program, but nothing gets printed.

In other words, the description of the message does not replace
the error.

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/diagnostics.pm b/lib/diagnostics.pm
index dc1a9b0f39..6c166a3b93 100644
--- a/lib/diagnostics.pm
+++ b/lib/diagnostics.pm
@@ -576,7 +576,10 @@ sub death_trap {
     # Have carp skip over death_trap() when showing the stack trace.
     local($Carp::CarpLevel) = 1;
 
-    confess "Uncaught exception from user code:\n\t$exception";
+    die Carp::longmess("__diagnostics__")
+	  =~ s/^__diagnostics__.*?line \d+\.?\n/
+		  "Uncaught exception from user code:\n\t$exception"
+	      /re;
 	# up we go; where we stop, nobody knows, but i think we die now
 	# but i'm deeply afraid of the &$olddie guy reraising and us getting
 	# into an indirect recursion loop