fix some 32/64-bit compiler warnings

Some bits of code don't do well on a 32-bit system with 64-bit ints
(-Duse64bitint)

In particular:

_MEM_WRAP_NEEDS_RUNTIME_CHECK:
    if sizeof(MEM_SIZE) > sizeof(n), then the shift count could be
        negative

S_regmatch:
    ln and n were two different sizes and signesses, so comparing them
    warned. Since they were being mis-used as two convenient temporary
    booleans anyway, just use temporary booleans instead.

Perl_sv_vcatpvfn_flags:
    the test/assertion (IV)elen < 0 was (I think) being used to test for
    signed/unsigned conversion wrap-around. elen is of type STRLEN which
    is a pointer-based type, so can be 32-bit while IV is 64-bit. Instead
    compare it to half the maximum value of a STRLEN var to see if it may
    have wrapped.

1 files changed, 6 insertions, 4 deletions

diff --git a/sv.c b/sv.c
index dc2ba8be39..feca75879a 100644
--- a/sv.c
+++ b/sv.c
@@ -11444,9 +11444,10 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
 		   is safe. */
 		is_utf8 = (bool)va_arg(*args, int);
 		elen = va_arg(*args, UV);
-                if ((IV)elen < 0) {
-                    /* check if utf8 length is larger than 0 when cast to IV */
-                    assert( (IV)elen >= 0 ); /* in DEBUGGING build we want to crash */
+                /* if utf8 length is larger than 0x7ffff..., then it might
+                 * have been a signed value that wrapped */
+                if (elen  > ((~(STRLEN)0) >> 1)) {
+                    assert(0); /* in DEBUGGING build we want to crash */
                     elen= 0; /* otherwise we want to treat this as an empty string */
                 }
 		eptr = va_arg(*args, char *);
@@ -12690,7 +12691,8 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
 	    }
 	}
 
-        assert((IV)elen >= 0); /* here zero elen is fine */
+        /* signed value that's wrapped? */
+        assert(elen  <= ((~(STRLEN)0) >> 1));
 	have = esignlen + zeros + elen;
 	if (have < zeros)
 	    croak_memory_wrap();