Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Control: clone -1 -2 Control: retitle -2 diffoscope: readelf(1): Ignore data/instruction addresses that are de facto line numbers Control: retitle -1 diffoscope: readelf(1): Reduce noise from deltas of offsets embedded in instructions Daniel Shahaf wrote on Tue, Sep 20, 2016 at 18:47:31 +: > However, in the .text section, each disassembled instruction is preceded > by its address. I think it would make sense to have the diff ignore > those addresses: they serve a purpose similar to line numbers, and > ignoring them cannot cause a difference to be missed. flexc++ has a difference on *every* line of several sections (.rodata, .eh_frame, others) because the sections start 0xc0 bytes later in the second build than in the first build: │ │ │ │ │ - 0x0043a320 01000200 623a423a 633a433a b:B:c:C: │ │ │ │ │ - 0x0043a330 64663a46 68693a49 3a4b6c3a 4c3a6d3a df:Fhi:I:Kl:L:m: ⋮ │ │ │ │ │ + 0x0043a3e0 01000200 623a423a 633a433a b:B:c:C: │ │ │ │ │ + 0x0043a3f0 64663a46 68693a49 3a4b6c3a 4c3a6d3a df:Fhi:I:Kl:L:m: Hence, filing this as a separate issue. #838260 can remain about offsets embedded in instructions. (It's safe to ignore these addresses because the start/end of the section already appear elsewhere in the diffed output.) ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Processed: Re: Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Processing control commands: > clone -1 -2 Bug #838260 [diffoscope] diffoscope: Reduce noise from offsets deltas in readelf(1) diffs Bug 838260 cloned as bug 838569 > retitle -2 diffoscope: readelf(1): Ignore data/instruction addresses that are > de facto line numbers Bug #838569 [diffoscope] diffoscope: Reduce noise from offsets deltas in readelf(1) diffs Changed Bug title to 'diffoscope: readelf(1): Ignore data/instruction addresses that are de facto line numbers' from 'diffoscope: Reduce noise from offsets deltas in readelf(1) diffs'. > retitle -1 diffoscope: readelf(1): Reduce noise from deltas of offsets > embedded in instructions Bug #838260 [diffoscope] diffoscope: Reduce noise from offsets deltas in readelf(1) diffs Changed Bug title to 'diffoscope: readelf(1): Reduce noise from deltas of offsets embedded in instructions' from 'diffoscope: Reduce noise from offsets deltas in readelf(1) diffs'. -- 838260: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=838260 838569: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=838569 Debian Bug Tracking System Contact ow...@bugs.debian.org with problems ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
> I was thinking of something like the HTML tag. In my browser, > foo renders «foo» with a dotted underline > whose raison d'être is your concern (a) Even so, you can't search the page with CTRL+F and, of course, it makes the output too different between --text and --html :) Anyway, small issue ... Regards, -- ,''`. : :' : Chris Lamb `. `'` la...@debian.org / chris-lamb.co.uk `- ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Chris Lamb wrote on Tue, Sep 20, 2016 at 20:58:29 +0100: > Daniel Shahaf wrote: > > > Example output: > > Alas I'm not very learned in ELF, so I will trust the specifics are fine, > but just to check: > I'm not too familiar with ELF either. I know a little about which C variables live in which section, e.g., .rodata is storage for string literals. > > > > .rodata#1 is 0xA70 > > .rodata#2 is 0xA80 > > … would be displayed (when different, of course!) as *something* like: > > - .rodata#1 is 0xA70 > + .rodata#1 is 0xA71 Yes. > > The actual hex values could be displayed as a tooltip on the 'lea' line, > > or appended to that line as a '# comment' > > So, tooltips are not only HTML-specific that would also hide data, > particularly > for a) users who do not even know they need to run their mouse over something, > b) users who generally drive their browser via a keyboard (probably more > common > for users of diffoscope!) and c) users with accessibility requirements. I was thinking of something like the HTML tag. In my browser, foo renders «foo» with a dotted underline whose raison d'être is your concern (a). I assume the user agents of people in categories (b) and (c) have similar solutions. In any case, displaying the values in a comment is probably better since it makes the information available without a user action. (As I said in my last email, the comment should be exempted from being diffed.) ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Daniel Shahaf wrote: > Example output: Alas I'm not very learned in ELF, so I will trust the specifics are fine, but just to check: > > .rodata#1 is 0xA70 > .rodata#2 is 0xA80 … would be displayed (when different, of course!) as *something* like: - .rodata#1 is 0xA70 + .rodata#1 is 0xA71 > The actual hex values could be displayed as a tooltip on the 'lea' line, > or appended to that line as a '# comment' So, tooltips are not only HTML-specific that would also hide data, particularly for a) users who do not even know they need to run their mouse over something, b) users who generally drive their browser via a keyboard (probably more common for users of diffoscope!) and c) users with accessibility requirements. Anyway, great idea - love it. Regards, -- ,''`. : :' : Chris Lamb `. `'` la...@debian.org / chris-lamb.co.uk `- ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Re: Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Jérémy Bobbio wrote: > Initially, I thought of this as a way to add image comparison as > felt sad not knowing any free software that could easily provide > similar features to what GitHub offers Pff, you don't like my existing image comparison? ;-) Regards, -- ,''`. : :' : Chris Lamb `. `'` la...@debian.org / chris-lamb.co.uk `- ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Daniel Shahaf: > Jérémy Bobbio wrote on Tue, Sep 20, 2016 at 13:18:49 +: >> But why stop with images? In the precise case of the readelf output, >> having line-oriented diff means we are carrying around a useless and >> confusing information: the line numbers are not helpful in anyway to >> locate and undrstand the differences. >> >> But what if we could replace the line numbers by the instruction >> addresses? Then the noise mentioned by Daniel disappears. Meanwhile, the >> actual output will become even more relevant. > > In the example in the OP, the (source code) line numbers and instruction > addresses are the same between both builds. It is the .rodata addresses > embeddded into the instructions that differ. Thanks for pointing this out, I had actually misunderstood the problem at hand. :) -- Lunar.''`. lunar at debian.org : :Ⓐ : # apt-get install anarchism `. `'` `- signature.asc Description: OpenPGP digital signature ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Jérémy Bobbio wrote on Tue, Sep 20, 2016 at 13:18:49 +: > But why stop with images? In the precise case of the readelf output, > having line-oriented diff means we are carrying around a useless and > confusing information: the line numbers are not helpful in anyway to > locate and undrstand the differences. > > But what if we could replace the line numbers by the instruction > addresses? Then the noise mentioned by Daniel disappears. Meanwhile, the > actual output will become even more relevant. In the example in the OP, the (source code) line numbers and instruction addresses are the same between both builds. It is the .rodata addresses embeddded into the instructions that differ. However, in the .text section, each disassembled instruction is preceded by its address. I think it would make sense to have the diff ignore those addresses: they serve a purpose similar to line numbers, and ignoring them cannot cause a difference to be missed. Cheers, Daniel ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Chris Lamb wrote on Tue, Sep 20, 2016 at 10:26:18 +0100: > > > Perhaps there is a perfect solution whereby we would normalise these two > > > offsets to — making it up here! — relative values, but simply need […] > > > > I'm not sure I understand what your idea is. Could you give an example > > of how the output might look? > > Apologies for not explaining myself better - I don't actually have a > concrete idea for the output, but I was just expressing a wish to avoid > a flag to ignore certain things so was using a hypothetical solution. Perhaps the output could replace all offsets into the .rodata section by sequential numbers? For example, if the .rodata section starts at 0xA00 and ends at 0xC00, and the output references 0xA80, 0xA70, 0xB80, and 0xB70, then those could be translated to .rodata#2, .rodata#1, .rodata#4, and .rodata#3 respectively. To make this lossless, the (.rodata#42 ↦ 0xB53) mapping could be appended to the file and included in the diff. Example output: lea«.rodata#1»(%rip),%rsi ⋮ .rodata#1 is 0xA70 .rodata#2 is 0xA80 The actual hex values could be displayed as a tooltip on the 'lea' line, or appended to that line as a '# comment' that will be considered equal by the unidiff (like 'diff -w' considers space and tab equal). Cheers, Daniel > We already have a few and I wish they would/could disappear! :) > > > Regards, > > -- > ,''`. > : :' : Chris Lamb > `. `'` la...@debian.org / chris-lamb.co.uk >`- ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
Bug#838260: diffoscope: Reduce noise from offsets deltas in readelf(1) diffs
Hi Daniel, > Could these offset differences in readelf(1) output be ignored, at least > optionally? Love the idea! However, my gut cautions against ignoring them. even with an option. Perhaps there is a perfect solution whereby we would normalise these two offsets to — making it up here! — relative values, but simply need to nclude that we have done that once in the diff. That way, we have a) still captured the underlying issue, b) reduced the noise, and c) avoided a cumbersome option flag. Regards, -- ,''`. : :' : Chris Lamb `. `'` la...@debian.org / chris-lamb.co.uk `- ___ Reproducible-builds mailing list Reproducible-builds@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/reproducible-builds
