[PATCH] D73269: [llvm-readobj] - Add a few warnings for --gnu-hash-table.

[George Rimar via Phabricator via llvm-commits]

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


================
Comment at: llvm/tools/llvm-readobj/ELFDumper.cpp:2525
+    // vector. We should not report a warning in this case.
+    bool IsEmptyHashTable =
+        GnuHashTable->symndx == NumSyms && BloomFilter.size() == 1 &&
----------------
MaskRay wrote:
> `GnuHashTable->symndx == 1` is probably sufficient.
> 
> The other conditions are redundant.
> GnuHashTable->symndx == 1 is probably sufficient.

It is not, because it can be > 1. For example when we have an object with an
undefined dynamic symbol and use lld:


**1.s:**
.global bar

```
as 1.s -o 1.o
lld 1.o -o 1.so -shared --hash-style=gnu
llvm-readelf --gnu-hash-table 1.so
```

```
GnuHashTable {
  Num Buckets: 1
  First Hashed Symbol Index: 2
  Num Mask Words: 1
  Shift Count: 26
  Bloom Filter: [0x0]
  Buckets: [0]
  Values: []
}
```

For GNU ld the output is different, btw (but it does not seem to be critical to fix LLD here, I guess):

```
ld.bfd 1.o -o 1.so -shared --hash-style=gnu
llvm-readelf --gnu-hash-table 1.so
```

```
GnuHashTable {
  Num Buckets: 1
  First Hashed Symbol Index: 1
  Num Mask Words: 1
  Shift Count: 0
  Bloom Filter: [0x0]
  Buckets: [0]
  Values: [0x0]
}
```



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  https://reviews.llvm.org/D73269/new/

https://reviews.llvm.org/D73269