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>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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