[PATCH] D81258: [yaml2obj] - Introduce a 10 Mb limit of the output by default and a --max-size option.

[George Rimar via Phabricator via llvm-commits]

grimar marked an inline comment as done.
grimar added inline comments.


================
Comment at: llvm/test/tools/yaml2obj/ELF/output-limit.yaml:10
+# RUN: yaml2obj %s -DSIZE=0x9FFEC0 --docnum=1 -o /dev/null 2>&1
+# RUN: not yaml2obj %s -DSIZE=0x9FFEC1 --docnum=1 -o /dev/null 2>&1 | \
+# RUN:  FileCheck %s --check-prefix=ERROR
----------------
jhenderson wrote:
> grimar wrote:
> > jhenderson wrote:
> > > I think it would be worthwhile testing a case where there is no section header table at all. This is because the `CBA` is not used to write the elf header and program header table.
> > I'd leave it for a follow-up:
> > 
> > we have an issue currently. Even when all headers are ommitted, we still write them:
> > 
> > ```
> >   State.writeELFHeader(OS, SHOff);
> >   writeArrayData(OS, makeArrayRef(PHeaders));
> >   CBA.writeBlobToStream(OS);
> >   writeArrayData(OS, makeArrayRef(SHeaders));
> >   return true;
> > ```
> > 
> > Instead we should write the number of headers specified in  `e_shnum`. Actually the logic should be even a bit more complex.
> > E.g. when the `e_shnum` (e.g 3) is overriden with the use of `SHNum` (e.g. 1), we should write the number of headers that would be written normally, i.e. 3, I think.
> > 
> > For now the condition I`ve used is intentionally simple and matches the current logic:
> > 
> > ```
> > SHOff + arrayDataSize(makeArrayRef(SHeaders)) > MaxSize
> > ```
> > 
> > This patch should allow to fix this issue nicely (will simplify writing a test).
> Doesn't `Sections: []` result in no sections (and therefore no section headers) at all?
If you mean just:

```
--- !ELF
FileHeader:
  Class:   ELFCLASS64
  Data:    ELFDATA2LSB
  Type:    ET_EXEC
  Machine: EM_X86_64
Sections: []
```

Then - no, the output will contain 2 implicit sections (.strtab and .shstrtab) + the SHF_UNDEF section at index 0.

Sections headers can be omitted with:

```
SectionHeaderTable:
  Sections: []
```

But because of the bug I've described, this only sets the `e_shoff` and `e_shnum` to 0,
but still writes the section header table which consumes the file size.


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  https://reviews.llvm.org/D81258/new/

https://reviews.llvm.org/D81258