flac decoder output buffer alignment

Hello,

I want to process the output from libflac with SSE/AVX. Unfortunately it
seems that libflac always allocates the output buffer itself and there
is no way to provide a buffer by the application.
 From my understanding of the code flac is using it's own functions in
share/alloc.h for allocations, and those use plain malloc. I assume the
only way to force aligned output buffers is to modify the alloc.h and
then link libflac statically and not use a system provided version?

I'm also open for any other flac decoding library (written in C or with
C header) that has the following features:

-Support seeking (with fast seeking using seektables if available)
-Support Ogg FLAC
-Fast decoding
-Should be able to handle *very long* flac files (like 2^40 samples).
libavcodec/ffmpeg fails at this, as some internal counter overflows

Best regards
Stefan