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• matroskadec : Add sizes to forward declarations

  17 juillet 2019, par Andreas Rheinhardt

  matroskadec : Add sizes to forward declarations
  Unknown-length elements end when an element not allowed in them, but
  
  allowed at a higher level is encountered. In order to check for this,
  
  c1abd95a added a pointer to every syntax level's parent to each
  
  EbmlSyntax. Given that the parent must of course also reference the
  
  child in order to be able to enter said child level, one needs to use
  
  forward declarations.
  
  These forward declarations constitute tentative definitions and tentative
  
  definitions with internal linkage (like our syntaxes) must not be an
  
  incomplete type. Yet they were an incomplete type and while GCC and
  
  Clang did not even warn about this (on default warning levels), it
  
  broke compilation with MSVC. Therefore this commit adds the sizes.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c

• oggparsedaala : reject too large gpshift

  29 décembre 2015, par Andreas Cadhalpun

  oggparsedaala : reject too large gpshift
  Also use a unsigned constant for the shift calculation, as 1 << 31 is
  
  undefined for int32_t. This is also fixed oggparsetheora.
  This fixes ubsan runtime error : shift exponent is too large for
  
  32-bit type ’int’
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
  

  • [DH] libavformat/oggparsedaala.c
  • [DH] libavformat/oggparsetheora.c

• avformat/matroskaenc : Make ebml_num_size() more robust

  2 avril 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Make ebml_num_size() more robust
  Matroska (or actually EBML) uses variable-length numbers where only
  
  seven bits of every byte is usable for the length ; the other bits encode
  
  the length of the variable-length number. So in order to find out how
  
  many bytes one needs to encode a given number one can use a loop like
  
  while (num >> 7 * bytes) bytes++ ; the Matroska muxer effectively did this.
  Yet it has a disadvantage : It is impossible for the result of a single
  
  right shift of an unsigned number with most significant bit set to be
  
  zero, because one can only shift by 0..(width - 1). On some
  
  architectures like x64 it is not even possible to do it with undefined
  
  right shifts in which case this leads to an infinite loop.
  This can be easily avoided by switching to a loop whose condition is
  
  (num >>= 7). The maximum value the so modified function can return
  
  is 10 ; any value > 8 is invalid and will now lead to an assert in
  
  put_ebml_num() or in start_ebml_master() (or actually in
  
  put_ebml_size_unknown()).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c