<div dir="ltr">I believe the compiler will generate a .debug_ranges section if you use -ffunction-sections, since the addresses of sections will be non-contiguous. From there, you should be able to edit the .debug_ranges assembly as needed (replace references to symbols with 0s in the .debug_ranges content) to get the exact behaviour you want (I'm assuming you don't want to have to hand-edit a .debug_abbrev/.debug_info data structure to manually create a .debug_ranges).<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, 26 Apr 2020 at 22:17, Greg Clayton via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;">Personally I generate DWARF with a python DWARF generator I wrote so I can make minimal test cases. I often can't get the compiler to emit what I need to test with DWARF. For example, I needed to create a compile unit with three functions: two of the functions need to look like they are dead stripped (with an address of zero) and they need to come first in the compile unit DW_AT_ranges. Also the compile unit needs to use a DW_AT_ranges attribute for the address ranges of each of the functions and I need to control the ordering. If I compile something like this from a source file, the compiler users a DW_AT_low_pc and DW_AT_high_pc and I have no DW_AT_ranges on the compile unit.<div><br></div><div>I was reproducing a bug in "llvm-dwarfdump --verify" and I fixed it and in order to check in a test case for this that isn't the huge example I started with I need to create exact DWARF that is as I detailed above. I can't get a .S file for my linked executable, and producing such an executable in the first place is not easy. So I find generating hand crafted DWARF easier. Then I just obj2yaml it, and I have my reduced test case. So it can be hard to get the compiler to emit test cases that are close enough to what I need in order to modify them at the .S file level.</div><div><br></div><div>That being said, the whole reason I wrote a DWARF generator was because the yaml stuff doesn't allow you to create a yaml file and edit it freely for reasons everyone else mentioned already (offsets mismatch, section sizes can't change easily, can't add attributes easily).</div><div><br></div><div>Does anyone have a way to create the kind of binary in a .S file that I mentioned above? The DWARF I need is in <a href="https://reviews.llvm.org/D78782" target="_blank">https://reviews.llvm.org/D78782</a> in the llvm/test/tools/obj2yaml/macho-DWARF-debug-ranges.yaml file on line 6 through line 31.</div><div><br></div><div>Greg</div><div><br></div><div><div><div><br><blockquote type="cite"><div>On Apr 24, 2020, at 6:21 AM, Pavel Labath <<a href="mailto:pavel@labath.sk" target="_blank">pavel@labath.sk</a>> wrote:</div><br><div><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">(Reviving this thread because a code review reminded me I want to reply</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">here. Sorry for the extremely long turnaround).</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">On 31/03/2020 20:22, Fangrui Song wrote:</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><blockquote type="cite" style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none">On 2020-03-31, Adrian Prantl via llvm-dev wrote:<br><blockquote type="cite"><br><br><blockquote type="cite">On Mar 31, 2020, at 10:55 AM, David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>> wrote:<br><br>+1 to all that & cc'ing a few of the usual suspects as FYI<br><br>On Tue, Mar 31, 2020 at 10:36 AM Pavel Labath via llvm-dev<br><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a> <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">mailto:llvm-dev@lists.llvm.org</a>>> wrote:<br><br><br>For me personally, the ability to write/edit syntactically correct dwarf<br>easily is much more important than being able to generate "incorrect"<br>dwarf -- I'm perfectly happy to continue to write the latter in<br>assembly, but there is a lot that could be improved about the experience<br>of writing "correct" dwarf. Ideally, I'd have a mode where I can just<br></blockquote><br>Do we think that yaml2obj is the best format for this, or would<br>high-level DWARF DIE assembler directives be a more useful abstraction<br>level? If you think about the .loc directive, there is actually some<br>prior art in assembler.<br><br>-- adrian<br></blockquote><br>I also find YAML tests unwieldy but for some tests (especiall malformed)<br>we may have to use them because it is diffult for an assembly directive<br>to produce invalid output (invalid offset/relocation/string table/etc).<br><br>An assembly syntax can be conciser than its YAML counterpart, e.g. to<br>describe a section:<br><br> <span> </span>assembly: .section .foo,"a",@progbits<br> <span> </span>YAML: - Name: foo<br> <span> </span>Type: SHT_PROGBITS<br> <span> </span>Flags: [ SHF_ALLOC ]<br><br>A symbol table entry is similar. A YAML entry usually takes several<br>lines of code.<br><br>Another advantage of assembly syntax is that it is composable. To define a<br>local symbol:<br><br> <span> </span>label:<br><br>To make it global:<br><br> <span> </span>.globl label<br> <span> </span>label:<br><br>Some directives are more expressive, e.g. .file .loc<br>An assembler even supports some meta programming features (macros). The<br>syntax may be strange.<br><br>We do need some composable directives to make DWARF tests easier to<br>write/read.<br></blockquote><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">I am agree with David that we shouldn't add first class DWARF-generation</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">directives to the assembler just for the sake of writing tests.</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">However, I do see the appeal of assembler metaprogramming, and I have</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">used it on occasion when generating some DWARF. A separate utility with</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">some (meta-)programming facilities could be interesting, though it would</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">be an additional burden to maintain, and I am not sure it is really</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">needed (in tests, repetition is often better than complex control flow).</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">I am curious about your comment on invalid relocations et al. I can see</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">how that is interesting for testing binary utilities (and I don't think</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">anyone wants to take that away), but I am not sure how useful is that in</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">the context of DWARF testing, except maybe in a couple of low-level</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">DWARF tests (which could be done in the traditional elf yaml and the</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">DWARF could be written as a blob of bytes). If you have some examples</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">like that, I'd very much like to about it.</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">regards,</span><br style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><span style="font-family:Menlo-Regular;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;float:none;display:inline">pl</span></div></blockquote></div><br></div></div></div>_______________________________________________<br>
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