1Fundamental design decision: 2 3- the sizes of external and internal types are assumed to be the same. 4 This leaves byte ordering aside. While assuming this the code can be 5 greatly simplified and speed increases. Since no change violating this 6 assumption is in sight this is believed to be a worthwhile optimization. 7 8- the ABI of the backend modules is not guaranteed. Really, no guarantee 9 whatsoever. We are enforcing this in the code. The modules and their 10 users must match. No third-party EBL module are supported or allowed. 11 The only reason there are separate modules is to not have the code for 12 all architectures in all the binaries. 13 14- although the public libraries (libasm, libdw) have a stable API and are 15 backwards ABI compatible they, and the elfutils tools, do depend on each 16 others internals, and on internals of libelf to provide their interfaces. 17 So they should always be upgraded in lockstep when packaging the tools 18 and libraries separately. For one example of how to do that, see the 19 config/elfutils.spec. 20 21Some notes: 22 23- old GNU ld's behavior wrt DSOs seems to be severely broken. 24 25 y.o reference foo() 26 y1.o defines foo(), references bar() 27 y2.o defines bar() 28 libbar.so defines bar() 29 30 Running 31 32 gcc -o y y.o -lbar y1.o y2.o 33 34 uses the bar() definition from libbar.so and does not mention the definition 35 in y2.o at all (no duplicate symbol message). Correct is to use the 36 definition in y2.o. 37 38 39 y.o reference foo() 40 y1.o defines foo(), references bar() 41 y2.o in liby2.a defines bar() 42 libbar.so defines bar() 43 44 Running 45 46 gcc -o y y.o -lbar y1.o -ly3 47 48 has to use the definition in -lbar and not pull the definition from liby3.a. 49 50 51- the old linker follows DT_NEEDED entries and adds the objects referenced 52 this way which define a symbol which is needed as a DT_NEEDED to the 53 generated binary. This is wrong since the DT_NEEDED changes the search 54 path in the object (which is breadth first). 55 56 57- the old linker supported extern "C++", extern "java" in version scripts. 58 I believe this implementation is severly broken and needs a redesign 59 (how do wildcards work with these languages*?). Therefore it is left 60 out for now. 61 62 63- what should happen if two sections in different files with the same 64 name have different types and/or the flags are different 65 66 67- section names in input files are mostly irrelevant. Exceptions: 68 69 .comment/SHT_PROGBITS in strip, ld 70 71 .debug \ 72 .line | 73 .debug_srcinfo | 74 .debug_sfnames | 75 .debug_aranges | 76 .debug_pubnames | 77 .debug_info | 78 .debug_abbrev | 79 .debug_line | 80 .debug_abbrev > DWARF sections in ld 81 .debug_line | 82 .debug_frame | 83 .debug_str | 84 .debug_loc | 85 .debug_macinfo | 86 .debug_weaknames | 87 .debug_funcnames | 88 .debug_typenames | 89 .debug_varnames / 90 91 Sections created in output files follow the naming of special section 92 from the gABI. 93 94 In no place is a section solely indentified by its name. Internal 95 references always use the section index. 96