$ gdb --args ~/repository/taglib/build/examples/tagreader taglib_oggflac_segfault.oga 
GNU gdb (Gentoo 7.7.1 p1) 7.7.1
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Reading symbols from /home/cocobo/repository/taglib/build/examples/tagreader...done.
(gdb) r
Starting program: /home/cocobo/repository/taglib/build/examples/tagreader taglib_oggflac_segfault.oga
warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
******************** "taglib_oggflac_segfault.oga" ********************

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7a0c9bc in TagLib::Ogg::FLAC::File::scan (this=0x617cd0)
    at /home/cocobo/repository/taglib/taglib/ogg/flac/oggflacfile.cpp:247
247       char blockType = header[0] & 0x7f;
(gdb) bt full
#0  0x00007ffff7a0c9bc in TagLib::Ogg::FLAC::File::scan (this=0x617cd0)
    at /home/cocobo/repository/taglib/taglib/ogg/flac/oggflacfile.cpp:247
        ipacket = 1
        overhead = 0
        metadataHeader = {_vptr.ByteVector = 0x7ffff7dce5f0 <vtable for TagLib::ByteVector+16>, 
          static null = {_vptr.ByteVector = 0x7ffff7dce5f0 <vtable for TagLib::ByteVector+16>, 
            static null = <same as static member of an already seen type>, d = 0x616b40}, 
          d = 0x6184a0}
        blockType = 90 'Z'
        lastBlock = 255
        length = 0
        header = {_vptr.ByteVector = 0x7ffff7dce5f0 <vtable for TagLib::ByteVector+16>, 
          static null = {_vptr.ByteVector = 0x7ffff7dce5f0 <vtable for TagLib::ByteVector+16>, 
            static null = <same as static member of an already seen type>, d = 0x616b40}, 
          d = 0x6194c0}
#1  0x00007ffff7a0baf4 in TagLib::Ogg::FLAC::File::read (this=0x617cd0, readProperties=true, 
    propertiesStyle=TagLib::AudioProperties::Average)
    at /home/cocobo/repository/taglib/taglib/ogg/flac/oggflacfile.cpp:164
No locals.
#2  0x00007ffff7a0aa45 in TagLib::Ogg::FLAC::File::File (this=0x617cd0, 
    file=0x7fffffffde7e "taglib_oggflac_segfault.oga", readProperties=true, 
    propertiesStyle=TagLib::AudioProperties::Average)
    at /home/cocobo/repository/taglib/taglib/ogg/flac/oggflacfile.cpp:77
No locals.
#3  0x00007ffff7b7aa8c in TagLib::FileRef::create (
    fileName=0x7fffffffde7e "taglib_oggflac_segfault.oga", readAudioProperties=true, 
    audioPropertiesStyle=TagLib::AudioProperties::Average)
    at /home/cocobo/repository/taglib/taglib/fileref.cpp:246
        file = 0x0
        it = 
        ext = {_vptr.String = 0x7ffff7dce4f0 <vtable for TagLib::String+16>, static null = {
            _vptr.String = 0x7ffff7dce4f0 <vtable for TagLib::String+16>, 
            static null = <same as static member of an already seen type>, 
            static WCharByteOrder = TagLib::String::UTF16LE, d = 0x616af0}, 
          static WCharByteOrder = TagLib::String::UTF16LE, d = 0x617db0}
#4  0x00007ffff7b77ad1 in TagLib::FileRef::FileRef (this=0x7fffffffd8d0, 
    fileName=0x7fffffffde7e "taglib_oggflac_segfault.oga", readAudioProperties=true, 
    audioPropertiesStyle=TagLib::AudioProperties::Average)
    at /home/cocobo/repository/taglib/taglib/fileref.cpp:83
No locals.
#5  0x00000000004048a7 in main (argc=2, argv=0x7fffffffda58)
    at /home/cocobo/repository/taglib/examples/tagreader.cpp:41
        f = {_vptr.FileRef = 0x7ffff7dd0610 <vtable for TagLib::FileRef+16>, d = 0x404792 <main+34>}
        i = 1
#6  0x00007ffff6c76dc5 in __libc_start_main () from /lib64/libc.so.6
No symbol table info available.
#7  0x00000000004046a9 in _start ()
No symbol table info available.
(gdb) list
242       //    ..
243       //    4 : VORBIS_COMMENT
244       //    ..
245       // <24> Length of metadata to follow
246
247       char blockType = header[0] & 0x7f;
248       bool lastBlock = (header[0] & 0x80) != 0;
249       uint length = header.toUInt(1, 3, true);
250       overhead += length;
251
(gdb) print header.size()
$1 = 0