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qsort isn't guaranteed to be a stable sort, that is, elements comparing equal according to the comparison function may be reordered relative to their original ordering. Of course sometimes you may not care, but even in those cases it is good to force some ordering (ie. not have the comparison function return 0) so that linker output is reproducible over different libc qsort implementations. One way to make qsort stable (which the glibc manual incorrectly says is the only way) is to augment the elements being sorted with a monotonic counter of some kind, and use that counter as the final arbiter of ordering in the comparison function. Another way is to set up an array of pointers into the array of elements, first pointer to first element, second pointer to second element and so so, and sort the pointer array rather than the element array. Final arbiter in the comparison function then is the pointer difference. This works well with, for example, the symbol pointers returned by _bfd_elf_canonicalize_symtab which point into a symbol array. This patch fixes a few places where sorting by symbol pointers is appropriate, and adds comments where qsort stability is a non-issue. * elf-strtab.c (strrevcmp): Comment. * merge.c (strrevcmp): Likewise. * elf64-ppc.c (compare_symbols): Correct final pointer comparison. Comment on why comparing pointers ensures a stable sort. * elflink.c (struct elf_symbol): Add void* to union. (elf_sort_elf_symbol): Ensure a stable sort with pointer comparison. (elf_sym_name_compare): Likewise. (bfd_elf_match_symbols_in_sections): Style fix. (elf_link_sort_cmp1): Comment.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.