site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com Message: 4 Date: Tue, 14 Sep 2004 00:29:19 -0400 From: "Mike Garey" <random50k@hotmail.com> Subject: Re: need help resolving symbols using twolevel hints table To: darwin-dev@lists.apple.com Message-ID: <BAY18-F35cF63W8qFs50011327d@hotmail.com> Content-Type: text/plain; format=flowed Thanks for the reply Bob, however, I'm still confused as to how you arrived at symbol number 4347 from printf having an itoc of 1854. I was thinking that perhaps the tocoff of libSystem + 1854 should equal 4347, but that's not the case. I've been reading the dyld sources, and it looks like they simply use the itoc as an initial starting position from which to begin a binary search. Although I'm unsure of how they perform a binary search on what seems like an unsorted list of symbols (because the symbol tables for mach-o images are not sorted), and if dyld was to sort its internal symbol list, I can't see how having the itoc would help, as it seems that the itoc is an index into the unsorted symbol table as it appears in the original mach-o image. Actually the symbols are sorted in a very specific way: local symbols sorted by module then by address external defined symbols sorted by module then by name undefined symbols (aka imported) sorted by name So anyways, is this itoc value, 1854, simply a suggesting starting point, and the value 4347 was found by performing a linear search from this index value? dysymtab_command.tocoff -> dylib_table_of_contents[1854].symbol_index == 4347 symtab_command.symoff -> n_list[4347] Also, another strange thing I noticed.. When using otool -Hv on a few different binaries, some show the itoc for printf to be 1854, while some others show the itoc to be 1855.. Any idea why this would happen? I guess maybe it depends on when the binary was built? My thinking is that it should, but you and I may have different system libraries. My libSystem.dylib is: otool -L /usr/lib/libSystem.dylib /usr/lib/libSystem.dylib: /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 71.1.1) /usr/lib/system/libmathCommon.A.dylib (compatibility version 1.0.0, current version 47.1.0) Note if the mach-o file is not a dylib (or is linked in single module mode) then all of the symbols are treated as if they are in a single module so they are only sorted by address. Also the DYSYMTAB contains indexes to the start and number of entries in each of these three groups. Actually it is possible that the local symbols are not normally sorted at all, it might be an artifact of the way I generate the symbol table. At index 1854 in the LC_DYSYMTAB is an entry which has the number 4347 which is an index into the n_list in the LC_SYMTAB: It might be the difference between the standard libSystem dylib vs libSystem_debug dylib (or _profile, or as you indicated being originally build against a different binary). Also I wrote my own Mach-O disassembler 7 years ago, which I use instead of Mach-O (it ships with the Metrowerks tools), so I am not up on all of the options to otool (I use it once in a while), but I sometimes wish otool would print more info (like the index of the entry when dumping the TOC) and it might be that I just am not finding the right option. Also the TOC is in my linker sources is sorted by name (no module) so using the itoc index from the linked application provide a good hint from which to start a binary search looking for the right value. -- Message Classification [x] General Business Information ___________________________________________________________________ Bob Campbell bobc@metrowerks.com 408.991.7490 _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... This email sent to site_archiver@lists.apple.com