sort { return foo() } ...

GH #18081

A sub call via return in a sort block was called in void rather than
scalar context, causing the comparison result to be discarded.

This because when a sort block is called it is not a real function
call, even though a sort block can be returned from. Instead, a
CXt_NULL is pushed on the context stack. Because this isn't a sub-ish
context type (unlike CXt_SUB, CXt_EVAL etc) there is no 'caller sub'
on the context stack to be found to retrieve the caller's context
(i.e. cx->cx_gimme).

This commit fixes it by special-casing Perl_gimme_V().

Ideally at some future point, a new context type, CXt_SORT, should be
added. This would be used instead of CXt_NULL when a sort BLOCK is
called. Like other sub-ish context types, it would have an old_cxsubix
field and PL_curstackinfo->si_cxsubix would point to it. This would
eliminate needing special-case handling in places like Perl_gimme_V().

1 files changed, 1 insertions, 1 deletions

diff --git a/inline.h b/inline.h
index a8240efb9c..6fbd5abfea 100644
--- a/inline.h
+++ b/inline.h
@@ -2086,7 +2086,7 @@ Perl_gimme_V(pTHX)
         return gimme;
     cxix = PL_curstackinfo->si_cxsubix;
     if (cxix < 0)
-        return G_VOID;
+        return PL_curstackinfo->si_type == PERLSI_SORT ? G_SCALAR: G_VOID;
     assert(cxstack[cxix].blk_gimme & G_WANT);
     return (cxstack[cxix].blk_gimme & G_WANT);
 }