amagic_call: accept a AMGf_force_scalar flag to force scalar context

and use it from the numeric comparison APIs.

Author: tonycoz

gv.c

@@ -3748,8 +3748,20 @@ The operation is done only on just one operand.
 
 The operation changes one of the operands, e.g., $x += 1
 
+=item C<AMGf_force_scalar>
+
+In many cases amagic_call() uses the L</GIMME_V> context of the
+current OP when calling the sub handling the overload.  This flag
+forces amagic_call() to use scalar context.
+
 =back
 
+=for apidoc Amnh||AMGf_noleft
+=for apidoc Amnh||AMGf_noright
+=for apidoc Amnh||AMGf_unary
+=for apidoc Amnh||AMGf_assign
+=for apidoc Amnh||AMGf_force_scalar
+
 =cut
 */
 
@@ -4142,7 +4154,8 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
                  * with the context of individual concats being scalar,
                  * regardless of the overall context of the multiconcat op
                  */
-    U8 gimme = (force_scalar || !PL_op || PL_op->op_type == OP_MULTICONCAT)
+    U8 gimme = (force_scalar || (flags & AMGf_force_scalar)
+                || !PL_op || PL_op->op_type == OP_MULTICONCAT)
                     ? G_SCALAR : GIMME_V;
 
     CATCH_SET(TRUE);

pp.h

@@ -653,14 +653,15 @@ Does not use C<TARG>.  See also C<L</XPUSHu>>, C<L</mPUSHu>> and C<L</PUSHu>>.
             (void)Perl_tmps_grow_p(aTHX_ eMiX);			\
     } STMT_END
 
-#define AMGf_noright	1
-#define AMGf_noleft	2
-#define AMGf_assign	4       /* op supports mutator variant, e.g. $x += 1 */
-#define AMGf_unary	8
-#define AMGf_numeric	0x10	/* for Perl_try_amagic_bin */
-
-#define AMGf_want_list	0x40
-#define AMGf_numarg	0x80
+#define AMGf_noright	  1
+#define AMGf_noleft	  2
+#define AMGf_assign	  4    /* op supports mutator variant, e.g. $x += 1 */
+#define AMGf_unary	  8
+#define AMGf_numeric	  0x0010   /* for Perl_try_amagic_bin */
+
+#define AMGf_want_list	  0x0040
+#define AMGf_numarg	  0x0080
+#define AMGf_force_scalar 0x0100
 
 
 /* do SvGETMAGIC on the stack args before checking for overload */

sv.c

@@ -8723,7 +8723,7 @@ S_sv_numcmp_common(pTHX_ SV **sv1, SV **sv2, const U32 flags,
 
     if(!(flags & SV_SKIP_OVERLOAD) &&
        (SvAMAGIC(*sv1) || SvAMAGIC(*sv2))) {
-        if ((*result = amagic_call(*sv1, *sv2, method, 0)))
+        if ((*result = amagic_call(*sv1, *sv2, method, AMGf_force_scalar)))
             return true;
 
         /* normally handled by try_amagic_bin */