[llvm-commits] PATCH: Fix ELFObjectFile::getSymbolAddress which make llvm-nm work incorrectly on executables

[Alexey Samsonov]

Hi!

libObject seems to incorrectly implement
ELFObjectFile::getSymbolAddress. See this reproducer:
$ cat main.cc
int main() {
  return 0;
}
$ g++ main.cc -o main.out
$ nm main.out | grep main
                 U __libc_start_main@@GLIBC_2.2.5
00000000004004b4 T main
$ llvm-nm main.out | grep main
         U __libc_start_main@@GLIBC_2.2.5
00800884 T main

Let's try to get what's wrong:
800884 - 4004b4 = 4003d0
$ objdump -h main.out | grep .text
 11 .text         000001c8  00000000004003d0  00000000004003d0  000003d0
 2**4

So, the symbol address is incorrectly incremented by the section offset. To
my understanding, attached patch should be applied to fix this. Please
check if this is ok to apply.
getSymbolFileOffset in the same file seems to be fine, at least according
to this quote from ELF specs:

Symbol table entries for different object file types have slightly
different interpretations for the st_value member.
<...>
* In relocatable files, st_value holds a section offset for a defined
symbol. That is, st_value is an offset from the beginning of the section
that st_shndx identifies.
* In executable and shared object files, st_value holds a virtual address.
[...]

-- 
Alexey Samsonov, MSK
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