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Ian, could you please take a look? I rebased the patch.. thank you, Alexander 2013/3/12 Alexander Ivchenko <aivchenk@gmail.com>: > *ping* > > thanks, > Alexander > > 2013/2/13 Alexander Ivchenko <aivchenk@gmail.com>: >>>The documentation of --sort-section=name for GNU ld is unfortunately >>>tied to the notion of a default linker script, which gold does not >>>share. Still, we ought to be able to come up with some plausible >>>meaning for gold. And restricting the behaviour to .data and .bss >>>does not make sense to me >> >> that's true, e.g for a testcase with .data and .sdata here what ld -M gave me: >> >> .data 0x0000000000600188 0xc >> *(SORT(.data) SORT(.data.*) SORT(.gnu.linkonce.d.*)) >> .data 0x0000000000600188 0x0 section_sorting_name_3.o >> .data 0x0000000000600188 0x0 section_sorting_name_1.o >> .data 0x0000000000600188 0x0 section_sorting_name_2.o >> .data.0001 0x0000000000600188 0x4 section_sorting_name_1.o >> 0x0000000000600188 vdata_0001 >> .data.0002 0x000000000060018c 0x4 section_sorting_name_2.o >> 0x000000000060018c vdata_0002 >> .data.0003 0x0000000000600190 0x4 section_sorting_name_3.o >> 0x0000000000600190 vdata_0003 >> >> .sdata.0003 0x0000000000600194 0x4 >> .sdata.0003 0x0000000000600194 0x4 section_sorting_name_3.o >> 0x0000000000600194 vsdata_0003 >> >> .sdata.0001 0x0000000000600198 0x4 >> .sdata.0001 0x0000000000600198 0x4 section_sorting_name_1.o >> 0x0000000000600198 vsdata_0001 >> >> .sdata.0002 0x000000000060019c 0x4 >> .sdata.0002 0x000000000060019c 0x4 section_sorting_name_2.o >> 0x000000000060019c vsdata_0002 >> >> It seems like there is no particular reason for not sorting .sdata >> sections: just BFD script doesn't do it. Therefore I agree with Sri >> when he said: >> >>>Why not sort all output sections when --sort-section=name is >>>specified? However, for special output sections like ctors, dtors, >>>init_array, fini_array, etc. the original sort compare function will >>>be used. For all other sections, use the new sort compare can be used. >>>No need to hard code any names. >> >> that approach looks reasonable. Also thank you very much, Sri, for >> your fix. I attached the patch with your >> changes and also with updated ChangLog. >> >> thanks, >> Alexander >> >> 2013/2/12 Sriraman Tallam <tmsriram@google.com>: >>> On Tue, Feb 12, 2013 at 10:22 AM, Sriraman Tallam <tmsriram@google.com> wrote: >>>> On Tue, Feb 12, 2013 at 9:21 AM, Ian Lance Taylor <iant@google.com> wrote: >>>>> On Tue, Feb 12, 2013 at 7:01 AM, Alexander Ivchenko <aivchenk@gmail.com> wrote: >>>>>> 2013/2/9 Ian Lance Taylor <iant@google.com>: >>>>>>> On Fri, Feb 8, 2013 at 5:11 PM, Ian Lance Taylor <iant@google.com> wrote: >>>>>>>> On Thu, Feb 7, 2013 at 3:56 AM, Alexander Ivchenko <aivchenk@gmail.com> wrote: >>>>>>>>> thank you for your help, Sri. I fixed help string and deleted warning. >>>>>>>>> >>>>>>>>> Ian, could you please take a look at the attached patch? >>>>>>>> >>>>>>>> As far as I can see, with this patch, when you use >>>>>>>> --sort-section=name, gold will only sort sections that start with >>>>>>>> .data. and .bss. by name. Other sections remain unsorted. This does >>>>>>>> not appear to be what the GNU linker does. The GNU linker appears to >>>>>>>> sort all input sections by name when using --sort-section=name. >>>>>>> >>>>>>> Sorry, I guess that's not quite right. You call the sorting code one >>>>>>> every section. But you only set must_sort_attached_input_sections on >>>>>>> the .data and .bss sections. How can you get away with that? >>>>>>> >>>>>>> Ian >>>>>> >>>>>> You mean from hardcoding those names (.bss and .data) there? I'm not >>>>>> sure so far, >>>>>> but I know that BFD sorts them by name when we have -sort-section=name >>>>>> and at the >>>>>> same time, BFD doesn't sort, say,.sdata and .sbss. >>>>>> Do we need to fully mimic the behavior of BFD for this option? >>>>> >>>>> We do not need to fully mimic GNU ld. However, we need to understand >>>>> how and why GNU ld behaves the way it does. When I look at the GNU ld >>>>> code, I don't see anything that restricts the effect of >>>>> --sort-section=name to the .data and .bss sections. Nor is it >>>>> documented to behave that way. >>>>> >>>>> The documentation of --sort-section=name for GNU ld is unfortunately >>>>> tied to the notion of a default linker script, which gold does not >>>>> share. Still, we ought to be able to come up with some plausible >>>>> meaning for gold. And restricting the behaviour to .data and .bss >>>>> does not make sense to me. >>>> >>>> Why not sort all output sections when --sort-section=name is >>>> specified? However, for special output sections like ctors, dtors, >>>> init_array, fini_array, etc. the original sort compare function will >>>> be used. For all other sections, use the new sort compare can be used. >>>> No need to hard code any names. >>>> >>>>> >>>>> Also, in order for this to work correctly, you must call >>>>> set_may_sort_attached_input_sections when you create the output >>>>> section. You aren't doing that, and I'm surprised that your code is >>>>> working reliably. >>>> >>>> I missed this part completely when I was reviewing his code, sorry!. I >>>> am not surprised his patch works for ".text" because the input >>>> sections are retained as he can piggy back on default text sorting. >>>> But, how does his test pass for bss and data? I will apply his patch >>>> and find out. >>> >>> I figured out how input sections are kept for some ".data" sections. >>> When the first object is seen, the isecn entries for its .data and >>> .bss are not kept. But after the first object, Layout::layout is >>> called which sets must_sort for .data and .bss. From then on, .data >>> and .bss are saved. This is definitely wrong. Infact, this patch does >>> not work correctly on the test case included and produces an assert in >>> reloc.cc:830 when I tried it. This is because some input section >>> entries have isecn and some do not. We encountered an instance of this >>> problem earlier with the text reordering patch. >>> >>> This can be fixed by removing the lines which set_must_sort in >>> Layout::layout and simply set_must_sort to all output sections in >>> Layout::make_output_section. Please note that setting may_sort and >>> then must_sort later is not necessary here since we know for sure that >>> we are going to sort this. >>> >>> I have modified this patch accordingly and attached a new patch that >>> sorts all output sections by name when --sort-section=name is passed. >>> For special output sections like .ctors, it will still use the >>> original sort compare function. I have not special cased if for >>> ".data" and ".bss" but I am not sure if ".sdata" and ".sbss" must be >>> ignored. >>> >>> Thanks >>> Sri >>> >>> >>> >>>> >>>> Sri >>>> >>>>> >>>>> Ian
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enable_sorting_sections_by_name_8.patch
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