Perl_magic_setdbline() should clear and set read-only OP slabs.

The debugger implements breakpoints by setting/clearing OPf_SPECIAL on
OP_DBSTATE ops. This means that it is writing to the optree at runtime,
and it falls foul of the enforced read-only OP slabs when debugging with
-DPERL_DEBUG_READONLY_OPS

Avoid this by removing static from Slab_to_rw(), and using it and Slab_to_ro()
in Perl_magic_setdbline() to temporarily make the slab re-write whilst
changing the breakpoint flag.

With this all tests pass with -DPERL_DEBUG_READONLY_OPS (on this system)

1 files changed, 6 insertions, 0 deletions

diff --git a/mg.c b/mg.c
index 3dea5c2ba4..1f6d0626a8 100644
--- a/mg.c
+++ b/mg.c
@@ -2020,11 +2020,17 @@ Perl_magic_setdbline(pTHX_ SV *sv, MAGIC *mg)
     if (svp && SvIOKp(*svp)) {
 	OP * const o = INT2PTR(OP*,SvIVX(*svp));
 	if (o) {
+#ifdef PERL_DEBUG_READONLY_OPS
+	    Slab_to_rw(OpSLAB(o));
+#endif
 	    /* set or clear breakpoint in the relevant control op */
 	    if (i)
 		o->op_flags |= OPf_SPECIAL;
 	    else
 		o->op_flags &= ~OPf_SPECIAL;
+#ifdef PERL_DEBUG_READONLY_OPS
+	    Slab_to_ro(OpSLAB(o));
+#endif
 	}
     }
     return 0;