Fundamental design decision: - the sizes of external and internal types are assumed to be the same.  This leaves byte ordering aside.  While assuming this the code can be  greatly simplified and speed increases.  Since no change violating this  assumption is in sight this is believed to be a worthwhile optimization. - the ABI of the backend modules is not guaranteed.  Really, no guarantee  whatsoever.  We are enforcing this in the code.  The modules and their  users must match.  No third-party EBL module are supported or allowed.  The only reason there are separate modules is to not have the code for  all architectures in all the binaries. - although the public libraries (libasm, libdw) have a stable API and are  backwards ABI compatible they, and the elfutils tools, do depend on each  others internals, and on internals of libelf to provide their interfaces.  So they should always be upgraded in lockstep when packaging the tools  and libraries separately. For one example of how to do that, see the  config/elfutils.spec. Some notes: - old GNU ld's behavior wrt DSOs seems to be severely broken.      y.o reference foo()     y1.o defines foo(), references bar()     y2.o defines bar()     libbar.so defines bar()   Running      gcc -o y y.o -lbar y1.o y2.o   uses the bar() definition from libbar.so and does not mention the definition  in y2.o at all (no duplicate symbol message).  Correct is to use the  definition in y2.o.       y.o reference foo()     y1.o defines foo(), references bar()     y2.o in liby2.a defines bar()     libbar.so defines bar()   Running      gcc -o y y.o -lbar y1.o -ly3   has to use the definition in -lbar and not pull the definition from liby3.a.  - the old linker follows DT_NEEDED entries and adds the objects referenced  this way which define a symbol which is needed as a DT_NEEDED to the  generated binary.  This is wrong since the DT_NEEDED changes the search  path in the object (which is breadth first).  - the old linker supported extern "C++", extern "java" in version scripts.  I believe this implementation is severly broken and needs a redesign  (how do wildcards work with these languages*?).  Therefore it is left  out for now.  - what should happen if two sections in different files with the same  name have different types and/or the flags are different  - section names in input files are mostly irrelevant.  Exceptions:   .comment/SHT_PROGBITS		in strip, ld   .debug		\  .line			|  .debug_srcinfo	|  .debug_sfnames	|  .debug_aranges	|  .debug_pubnames	|  .debug_info		|  .debug_abbrev		|  .debug_line		|  .debug_abbrev		 >	DWARF sections in ld  .debug_line		|  .debug_frame		|  .debug_str		|  .debug_loc		|  .debug_macinfo	|  .debug_weaknames	|  .debug_funcnames	|  .debug_typenames	|  .debug_varnames	/   Sections created in output files follow the naming of special section  from the gABI.   In no place is a section solely indentified by its name.  Internal  references always use the section index.