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2011-11-17Allow refc binaries in literal poolsBjörn Gustavsson
To simplify the implementation of literal pools (constant pools) for the R12 release, a shortcut was taken regarding binaries -- all binaries would be stored as heap binaries regardless of size. To allow a module containing literals to be unloaded, literal terms are copied when sent to another process. That means that huge literal binaries will also be copied if they are sent to another process, which could be surprising. Another problem is that the arity field in the header for the heap object may not be wide enough to handle big binaries. Therefore, bite the bullet and allow refc binaries to be stored in literal pools. In short, the following need to be changed: * Each loaded module needs a MSO list, linking all refc binaries in the literal pool. * When check_process_code/2 copies literals to a process heap, it must link each referenced binary into the MSO list for the process and increment the reference counter for the binary. * purge_module/1 must decrement the reference counter for each refc binary in the literal pool.
2011-11-07beam_asm: Strenghten the calculation of Uniq for funsBjörn Gustavsson
Funs are identified by a triple, <Module,Uniq,Index>, where Module is the module name, Uniq is a 27 bit hash value of some intermediate representation of the code for the fun, and index is a small integer. When a fun is loaded, the triple for the fun will be compared to previously loaded funs. If all elements in the triple in the newly loaded fun are the same, the newly loaded fun will replace the previous fun. The idea is that if Uniq are the same, the code for the fun is also the same. The problem is that Uniq is only based on the intermediate representation of the fun itself. If the fun calls local functions in the same module, Uniq may remain the same even if the behavior of the fun has been changed. See http://erlang.org/pipermail/erlang-bugs/2007-June/000368.htlm for an example. As a long-term plan to fix this problem, the NewIndex and NewUniq fields was added to each fun in the R8 release (where NewUniq is the MD5 of the BEAM code for the module). Unfortunately, it turns out that the compiler does not assign unique value to NewIndex (if it isn't tested, it doesn't work), so we cannot use the <Module,NewUniq,NewIndex> triple as identification. It would be possible to use <Module,NewUniq,Index>, but that seems ugly. Therefore, fix the problem by making Uniq more unique by taking 27 bits from the MD5 for the BEAM code. That only requires a change to the compiler. Also update a test case for cover, which now fails because of the stronger Uniq calculation. (The comment in test case about why the Pid2 process survived is not correct.)
2009-11-20The R13B03 release.OTP_R13B03Erlang/OTP