X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/ef058b33cd10c03cc5704ec5447df1d23fe3b48b..ec5bd2262bb4e28f0dc6a0a3edb9b1f1b5befa2f:/sv.h

diff --git a/sv.h b/sv.h
index 2b68682..bfda6bf 100644
--- a/sv.h
+++ b/sv.h
@@ -467,7 +467,7 @@ perform the upgrade if necessary.  See C<L</svtype>>.
 /* PVHV */
 #define SVphv_HASKFLAGS	0x80000000  /* keys have flag byte after hash */
 /* PVGV when SVpbm_VALID is true */
-#define SVpbm_TAIL	0x80000000
+#define SVpbm_TAIL	0x80000000  /* string has a fake "\n" appended */
 /* RV upwards. However, SVf_ROK and SVp_IOK are exclusive  */
 #define SVprv_WEAKREF   0x80000000  /* Weak reference */
 /* pad name vars only */
@@ -838,7 +838,7 @@ Set the current length of the string which is in the SV.  See C<L</SvCUR>>
 and C<SvIV_set>>.
 
 =for apidoc Am|void|SvLEN_set|SV* sv|STRLEN len
-Set the actual length of the string which is in the SV.  See C<L</SvIV_set>>.
+Set the size of the string buffer for the SV. See C<L</SvLEN>>.
 
 =cut
 */
@@ -949,7 +949,7 @@ in gv.h: */
 
 #define SvOOK(sv)		(SvFLAGS(sv) & SVf_OOK)
 #define SvOOK_on(sv)		(SvFLAGS(sv) |= SVf_OOK)
-#define SvOOK_off(sv)		((void)(SvOOK(sv) && sv_backoff(sv)))
+#define SvOOK_off(sv)		((void)(SvOOK(sv) && (sv_backoff(sv),0)))
 
 #define SvFAKE(sv)		(SvFLAGS(sv) & SVf_FAKE)
 #define SvFAKE_on(sv)		(SvFLAGS(sv) |= SVf_FAKE)
@@ -1473,10 +1473,9 @@ attention to precisely which outputs are influenced by which inputs.
 
 #define SvTAINT(sv)			\
     STMT_START {			\
-	if (UNLIKELY(TAINTING_get)) {	\
-	    if (UNLIKELY(TAINT_get))	\
-		SvTAINTED_on(sv);	\
-	}				\
+        assert(TAINTING_get || !TAINT_get); \
+        if (UNLIKELY(TAINT_get))	\
+            SvTAINTED_on(sv);	        \
     } STMT_END
 
 /*
@@ -2261,5 +2260,39 @@ Evaluates C<sv> more than once.  Sets C<len> to 0 if C<SvOOK(sv)> is false.
 #define SV_CONSTS_COUNT 35
 
 /*
+ * Bodyless IVs and NVs!
+ *
+ * Since 5.9.2, we can avoid allocating a body for SVt_IV-type SVs.
+ * Since the larger IV-holding variants of SVs store their integer
+ * values in their respective bodies, the family of SvIV() accessor
+ * macros would  naively have to branch on the SV type to find the
+ * integer value either in the HEAD or BODY. In order to avoid this
+ * expensive branch, a clever soul has deployed a great hack:
+ * We set up the SvANY pointer such that instead of pointing to a
+ * real body, it points into the memory before the location of the
+ * head. We compute this pointer such that the location of
+ * the integer member of the hypothetical body struct happens to
+ * be the same as the location of the integer member of the bodyless
+ * SV head. This now means that the SvIV() family of accessors can
+ * always read from the (hypothetical or real) body via SvANY.
+ *
+ * Since the 5.21 dev series, we employ the same trick for NVs
+ * if the architecture can support it (NVSIZE <= IVSIZE).
+ */
+
+/* The following two macros compute the necessary offsets for the above
+ * trick and store them in SvANY for SvIV() (and friends) to use. */
+
+#ifdef PERL_CORE
+#  define SET_SVANY_FOR_BODYLESS_IV(sv) \
+	SvANY(sv) =   (XPVIV*)((char*)&(sv->sv_u.svu_iv) \
+                    - STRUCT_OFFSET(XPVIV, xiv_iv))
+
+#  define SET_SVANY_FOR_BODYLESS_NV(sv) \
+	SvANY(sv) =   (XPVNV*)((char*)&(sv->sv_u.svu_nv) \
+                    - STRUCT_OFFSET(XPVNV, xnv_u.xnv_nv))
+#endif
+
+/*
  * ex: set ts=8 sts=4 sw=4 et:
  */