Fix for #71506: work around possible gcc bug

When memcpy() is used on a long double pointer with gcc 4.4 in some
cases it seems to treat it as a long double assignment, copying only
the first 12 bytes.  Use unions so the types we're copying into the
pack output or from the unpack input are unsigned char[], to avoid the
apparent bug.

diff --git a/pp_pack.c b/pp_pack.c
index 03eaf7f..0670548 100644 (file)
--- a/pp_pack.c
+++ b/pp_pack.c
@@ -70,6 +70,18 @@ typedef struct tempsym {
        (symptr)->previous = NULL;      \
    } STMT_END
 
+typedef union {
+    NV nv;
+    U8 bytes[sizeof(NV)];
+} NV_bytes;
+
+#if defined(HAS_LONG_DOUBLE) && defined(USE_LONG_DOUBLE)
+typedef union {
+    long double ld;
+    U8 bytes[sizeof(long double)];
+} ld_bytes;
+#endif
+
 #if PERL_VERSION >= 9
 # define PERL_PACK_CAN_BYTEORDER
 # define PERL_PACK_CAN_SHRIEKSIGN
@@ -146,17 +158,20 @@ typedef struct tempsym {
 #define PUSH32(utf8, cur, p) PUSH_BYTES(utf8, cur, OFF32(p), SIZE32)
 
 /* Only to be used inside a loop (see the break) */
-#define SHIFT_VAR(utf8, s, strend, var, datumtype)     \
+#define SHIFT_BYTES(utf8, s, strend, buf, len, datumtype)      \
 STMT_START {                                           \
     if (utf8) {                                                \
         if (!uni_to_bytes(aTHX_ &s, strend,            \
-            (char *) &var, sizeof(var), datumtype)) break;\
+         (char *) (buf), len, datumtype)) break;       \
     } else {                                           \
-        Copy(s, (char *) &var, sizeof(var), char);     \
-        s += sizeof(var);                              \
+        Copy(s, (char *) (buf), len, char);            \
+        s += len;                                      \
     }                                                  \
 } STMT_END
 
+#define SHIFT_VAR(utf8, s, strend, var, datumtype)     \
+       SHIFT_BYTES(utf8, s, strend, &(var), sizeof(var), datumtype)
+
 #define PUSH_VAR(utf8, aptr, var)      \
        PUSH_BYTES(utf8, aptr, &(var), sizeof(var))
 
@@ -2085,25 +2100,25 @@ S_unpack_rec(pTHX_ tempsym_t* symptr, const char *s, const char *strbeg, const c
            break;
        case 'F':
            while (len-- > 0) {
-               NV anv;
-               SHIFT_VAR(utf8, s, strend, anv, datumtype);
-               DO_BO_UNPACK_N(anv, NV);
+               NV_bytes anv;
+               SHIFT_BYTES(utf8, s, strend, anv.bytes, sizeof(anv.bytes), datumtype);
+               DO_BO_UNPACK_N(anv.nv, NV);
                if (!checksum)
-                   mPUSHn(anv);
+                   mPUSHn(anv.nv);
                else
-                   cdouble += anv;
+                   cdouble += anv.nv;
            }
            break;
 #if defined(HAS_LONG_DOUBLE) && defined(USE_LONG_DOUBLE)
        case 'D':
            while (len-- > 0) {
-               long double aldouble;
-               SHIFT_VAR(utf8, s, strend, aldouble, datumtype);
-               DO_BO_UNPACK_N(aldouble, long double);
+               ld_bytes aldouble;
+               SHIFT_BYTES(utf8, s, strend, aldouble.bytes, sizeof(aldouble.bytes), datumtype);
+               DO_BO_UNPACK_N(aldouble.ld, long double);
                if (!checksum)
-                   mPUSHn(aldouble);
+                   mPUSHn(aldouble.ld);
                else
-                   cdouble += aldouble;
+                   cdouble += aldouble.ld;
            }
            break;
 #endif
@@ -3156,26 +3171,26 @@ extern const double _double_constants[];
            }
            break;
        case 'F': {
-           NV anv;
+           NV_bytes anv;
            Zero(&anv, 1, NV); /* can be long double with unused bits */
            while (len-- > 0) {
                fromstr = NEXTFROM;
-               anv = SvNV(fromstr);
+               anv.nv = SvNV(fromstr);
                DO_BO_PACK_N(anv, NV);
-               PUSH_VAR(utf8, cur, anv);
+               PUSH_BYTES(utf8, cur, anv.bytes, sizeof(anv.bytes));
            }
            break;
        }
 #if defined(HAS_LONG_DOUBLE) && defined(USE_LONG_DOUBLE)
        case 'D': {
-           long double aldouble;
+           ld_bytes aldouble;
            /* long doubles can have unused bits, which may be nonzero */
            Zero(&aldouble, 1, long double);
            while (len-- > 0) {
                fromstr = NEXTFROM;
-               aldouble = (long double)SvNV(fromstr);
+               aldouble.ld = (long double)SvNV(fromstr);
                DO_BO_PACK_N(aldouble, long double);
-               PUSH_VAR(utf8, cur, aldouble);
+               PUSH_BYTES(utf8, cur, aldouble.bytes, sizeof(aldouble.bytes));
            }
            break;
        }