Does not work in perl 5.20.1

[GoogleCodeExporter]

What steps will reproduce the problem?

1. Patch protobuf-perlxs-1.1/examples/embedded with the following:
Index: examples/embedded/test.pl
===================================================================
--- examples/embedded/test.pl   (revision 191663)
+++ examples/embedded/test.pl   (working copy)
@@ -84,6 +84,8 @@
     my $packed  = $error->pack;
     my $length  = length($packed);
     my $elapsed = tv_interval($now);
+    $error->clear();
+    $error->unpack($packed);

     print "Built/packed error of $length bytes in $elapsed seconds\n";

@@ -116,6 +118,8 @@
     my $packed  = $error->pack;
     my $length  = length($packed);
     my $elapsed = tv_interval($now);
+    $error->clear();
+    $error->unpack($packed);

     print "Built/packed error of $length bytes in $elapsed seconds\n";

2. perl Makefile.PL && make && make test

What is the expected output? What do you see instead?
I see output like this:

        Built/packed error of 141 bytes in 6.8e-05 seconds
        $VAR1 = {
                  'datetime' => 1415276412,
                  'severity' => 3,
                  'message' => 'Here iing"

        test'
                };
        Built/packed error of 141 bytes in 6.2e-05 seconds
        $VAR1 = {
                  'message' => 'Here iing"

        test',
                  'datetime' => 1415276412,
                  'severity' => 3
                };

instead of

        Built/packed error of 173 bytes in 7.7e-05 seconds
        $VAR1 = {
                  'pid' => 29231,
                  'message' => 'Here is a warning',
                  'trace' => [
                               {
                                 'file' => 'test.pl',
                                 'line' => 51
                               },
                               {
                                 'line' => 43,
                                 'file' => 'test.pl'
                               },
                               {
                                 'line' => 39,
                                 'file' => 'test.pl'
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 35
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 31
                               },
                               {
                                 'line' => 27,
                                 'file' => 'test.pl'
                               },
                               {
                                 'line' => 23,
                                 'file' => 'test.pl'
                               },
                               {
                                 'line' => 19,
                                 'file' => 'test.pl'
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 15
                               },
                               {
                                 'line' => 11,
                                 'file' => 'test.pl'
                               }
                             ],
                  'hostname' => 'spider-man',
                  'severity' => 3,
                  'datetime' => 1415276538
                };
        Built/packed error of 173 bytes in 6.1e-05 seconds
        $VAR1 = {
                  'pid' => 29231,
                  'message' => 'Here is a warning',
                  'trace' => [
                               {
                                 'file' => 'test.pl',
                                 'line' => 51
                               },
                               {
                                 'line' => 43,
                                 'file' => 'test.pl'
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 39
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 35
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 31
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 27
                               },
                               {
                                 'line' => 23,
                                 'file' => 'test.pl'
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 19
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 15
                               },
                               {
                                 'file' => 'test.pl',
                                 'line' => 12
                               }
                             ],
                  'datetime' => 1415276538,
                  'severity' => 3,
                  'hostname' => 'spider-man'
                };

What version of the product are you using? On what operating system?
- protobuf-perlxs-1.1
- Ubuntu 14.10
- $ perl -v

        This is perl 5, version 20, subversion 1 (v5.20.1) built for x86_64-linux-gnu-thread-multi
        (with 37 registered patches, see perl -V for more detail)

Please provide any additional information below.
I fixed this by that patch:
Index: src/google/protobuf/compiler/perlxs/perlxs_generator.cc
===================================================================
--- src/google/protobuf/compiler/perlxs/perlxs_generator.cc (revision 191667)
+++ src/google/protobuf/compiler/perlxs/perlxs_generator.cc (working copy)
@@ -123,21 +123,19 @@
   printer.Print("class $base$_OutputStream :\n"
        "  public google::protobuf::io::ZeroCopyOutputStream {\n"
        "public:\n"
+       "  explicit $base$_OutputStream(SV * sv) : sv_(sv) {}\n"
-       "  explicit $base$_OutputStream(SV * sv) :\n"
-       "  sv_(sv), len_(0) {}\n"
        "  ~$base$_OutputStream() {}\n"
        "\n"
        "  bool Next(void** data, int* size)\n"
        "  {\n"
+       "    STRLEN byteCount = SvCUR(sv_);\n"
+       "    STRLEN available = SvLEN(sv_) - byteCount;\n"
+       "    if (available <= 16)\n"
+       "    {\n"
+       "      SvGROW(sv_, 2 * byteCount);\n"
+       "      available = SvLEN(sv_) - byteCount;\n"
+       "    }\n"
+       "    SvCUR_set(sv_, byteCount + available);\n"
+       "    *data = SvPVX(sv_) + byteCount;\n"
+       "    *size = available;\n"
-       "    STRLEN nlen = len_ << 1;\n"
-       "\n"
-       "    if ( nlen < 16 ) nlen = 16;\n"
-       "    SvGROW(sv_, nlen);\n"
-       "    *data = SvEND(sv_) + len_;\n"
-       "    *size = SvLEN(sv_) - len_;\n"
-       "    len_ = nlen;\n"
        "\n"
        "    return true;\n"
        "  }\n"
@@ -147,7 +145,11 @@
        "    SvCUR_set(sv_, SvLEN(sv_) - count);\n"
        "  }\n"
        "\n"
+       "  void Sync() {}\n"
-       "  void Sync() {\n"
-       "    if ( SvCUR(sv_) == 0 ) {\n"
-       "      SvCUR_set(sv_, len_);\n"
-       "    }\n"
-       "  }\n"
        "\n"
        "  int64_t ByteCount() const\n"
        "  {\n"
@@ -156,6 +158,7 @@
        "\n"
        "private:\n"
        "  SV * sv_;\n"
-       "  STRLEN len_;\n"
        "\n"
        "  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS($base$_OutputStream);\n"
        "};\n"

Original issue reported on code.google.com by s2...@land.ru on 6 Nov 2014 at 12:32