Also document and unit-test the correct handling of UTF-8

Author: leonerd

ext/XS-APItest/t/sv_streq.t

@@ -1,13 +1,27 @@
 #!perl
 
-use Test::More tests => 7;
+use Test::More tests => 9;
 use XS::APItest;
 
 my $abc = "abc";
 ok  sv_streq($abc, "abc"), '$abc eq "abc"';
 ok !sv_streq($abc, "def"), '$abc ne "def"';
 
-# consider also UTF-8 vs not
+{
+    # U+00E9 = LATIN SMALL LETTER E WITH ACUTE
+    #  UTF-8: \xc3 \xa9
+    my $cafe_LATIN1 = "caf\xe9";
+    utf8::upgrade(my $cafe_UNICODE = "caf\x{00e9}");
+    utf8::encode (my $cafe_UTF8    = "caf\x{00e9}");
+
+    # Latin-1 and Unicode strings should compare equal despite containing
+    # different underlying bytes in the SvPV
+    ok sv_streq($cafe_LATIN1, $cafe_UNICODE), 'sv_streq handles UTF8 strings';
+
+    # UTF-8 and Unicode strings should not compare equal, even though they
+    # contain the same bytes in the SvPV
+    ok !sv_streq($cafe_UTF8, $cafe_UNICODE), 'sv_streq takes UTF8ness into account';
+}
 
 # GMAGIC
 "ABC" =~ m/(\w+)/;

sv.c

@@ -8191,7 +8191,7 @@ Perl_sv_eq_flags(pTHX_ SV *sv1, SV *sv2, const U32 flags)
 Returns a boolean indicating whether the strings in the two SVs are
 identical. If the flags argument has the C<SV_GMAGIC> bit set, it handles
 get-magic too. Will coerce its args to strings if necessary. Treats
-C<NULL> as undef.
+C<NULL> as undef. Correctly handles the UTF8 flag.
 
 If flags does not have the C<SV_SKIP_OVERLOAD> bit set, an attempt to use
 C<eq> overloading will be made. If such overloading does not exist or the