[PATCH] D69997: [llvm-objdump] Print relocation addends in hexadecimal

[Dave Bozier via Phabricator via llvm-commits]

davidb marked 5 inline comments as done.
davidb added inline comments.


================
Comment at: llvm/tools/llvm-objdump/ELFDump.cpp:113
+      if (Addend < 0)
+        Addend = -Addend;
+
----------------
MaskRay wrote:
> davidb wrote:
> > jhenderson wrote:
> > > davidb wrote:
> > > > jhenderson wrote:
> > > > > davidb wrote:
> > > > > > jhenderson wrote:
> > > > > > > davidb wrote:
> > > > > > > > jhenderson wrote:
> > > > > > > > > Won't this fail for minimum int64_t?
> > > > > > > > Yes. Is there a better abs implementation or function in LLVM that works around this case?
> > > > > > > I'm not aware of one, unfortunately, but do you need it?
> > > > > > > 
> > > > > > > My reading of the code is that format(AddendFmt, Addend) combined with the PRIx64 (which uses a signed integer type) you used above should be sufficient.
> > > > > > Yes, I need the absolute value for the string representation so `foo-0x4` rather than `foo+0xfffffffc`....
> > > > > Right, of course, sorry.
> > > > > 
> > > > > The answer to [[ https://stackoverflow.com/questions/17313579/is-there-a-safe-way-to-get-the-unsigned-absolute-value-of-a-signed-integer-with | this stack overflow post ]] suggests the way to do it is to cast the type to the unsigned equivalent and then negating it (rather than the other way around). I haven't tested that this works though. You should add a test case for it.
> > > > Might be tricky given that objtoyaml can't seem to parse large signed integers,
> > > yaml2obj can handle the following yaml fine for me (the integer is 0x8000000000000000):
> > > 
> > > ```
> > > --- !ELF
> > > FileHeader:
> > >   Class:   ELFCLASS64
> > >   Data:    ELFDATA2LSB
> > >   Type:    ET_REL
> > >   Machine: EM_X86_64
> > > Sections:
> > >   - Name:    .foo
> > >     Type:    SHT_PROGBITS
> > >   - Name:    .rela.foo
> > >     Type:    SHT_RELA
> > >     Info:    .foo
> > >     Relocations:
> > >       - Offset: 0
> > >         Symbol: foo
> > >         Type: R_X86_64_NONE
> > >         Addend: -9223372036854775808
> > > Symbols:
> > >   - Name: foo
> > > ```
> > Yeah, strange.... maybe I had a typo in my Addend... working now.
> I think std::abs is very inconvenient here.
> 
> Probably just use `Addend < 0 ? -(uint64_t)Addend : (uint64_t)Addend`
> 
> `(uint64_t)INT64_MIN` is implementation-defined before C++20 and defined since C++20. "implementation-defined" does not matter, because there is so much code that relies on similar implementation defined behaviors.
Good to know, thank you!


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69997/new/

https://reviews.llvm.org/D69997