snappy: @1.1.9: buildbot failures for macOS 10.8 through 10.14

[mascguy (Christopher Nielsen)]

This port is failing to build on most of our buildbots, following the 1.1.9 port update:

​https://github.com/macports/macports-ports/commit/14620b1c10dc90e0cb3edc699b5f45feed422569

10.14 fails with:

.../work/snappy-1.1.9/snappy.cc:1033:36: error: invalid output constraint '=@ccz' in asm
      : [tag_type] "+r"(tag_type), "=@ccz"(is_literal));
                                   ^
1 error generated.
make[2]: *** [CMakeFiles/snappy.dir/snappy.cc.o] Error 1

While most of the others fail with this:

work/snappy-1.1.9/snappy.cc:133:35: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
  return std::array<int16_t, 256>{LengthMinusOffset(seq)...};
                                  ^~~~~~~~~~~~~~~~~~~~~~
                                  {                     }
work/snappy-1.1.9/snappy.cc:141:12: note: in instantiation of function template specialization 'snappy::(anonymous namespace)::MakeTable<0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255>' requested here
} table = {MakeTable(make_index_sequence<256>{}), {0, 0xFF, 0xFFFF, 0}};
           ^
work/snappy-1.1.9/snappy.cc:245:11: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
  return {static_cast<char>((index_offset + indexes) % pattern_size)...};
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          {                                                         }
work/snappy-1.1.9/snappy.cc:255:11: note: in instantiation of function template specialization 'snappy::(anonymous namespace)::MakePatternMaskBytes<0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15>' requested here
  return {MakePatternMaskBytes(
          ^
work/snappy-1.1.9/snappy.cc:255:11: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
  return {MakePatternMaskBytes(
          ^~~~~~~~~~~~~~~~~~~~~
          {
work/snappy-1.1.9/snappy.cc:265:5: note: in instantiation of function template specialization 'snappy::(anonymous namespace)::MakePatternMaskBytesTable<0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15>' requested here
    MakePatternMaskBytesTable(
    ^
work/snappy-1.1.9/snappy.cc:1033:36: error: invalid output constraint '=@ccz' in asm
      : [tag_type] "+r"(tag_type), "=@ccz"(is_literal));
                                   ^
4 errors generated.
make[2]: *** [CMakeFiles/snappy.dir/snappy.cc.o] Error 1

Do we need to blacklist older compilers, and/or declare a newer C/C++ standard?

[mascguy (Christopher Nielsen)]

Of note, buildbot builds are failing, across a range of macOS releases. Interestingly enough, though, it is compiling on 10.6 and 10.7, but failing on 10.8 through 10.14. So I'm wondering if we need to force a newer Clang version across-the-board (like Clang 9).

​https://ports.macports.org/port/snappy/builds

[mascguy (Christopher Nielsen)]

EDIT: Updated the description with latest info; this comment now obsolete.