[PATCH] D47602: Correct aligment computation for shared object symbols

[Han Shen via Phabricator via llvm-commits]

shenhan added inline comments.


================
Comment at: ELF/InputFiles.cpp:899
+  // If no available alignment information from either section or
+  // symbol, return 1.
+  if (!(Sym.st_value || (0 < Sym.st_shndx && Sym.st_shndx < Sections.size())))
----------------
pcc wrote:
> Is that correct? If there is a symbol at virtual address 0 in an unknown section, doesn't that mean that we should error out via the `Ret > UINT32_MAX` code path below since we don't know what alignment to use?
We have quite a few tests that link with libm.so, which has quite a few symbols with st_value as 0 and shndx as "ABS".  Shall we handle symbols with "ABS" shndex separately (if symbols has absolute address, linker does not need to change its address or its address is not relevant, right?) 

   221: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.4
   238: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.2.5
   394: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.15
   399: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.18
  1736: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.15
  1922: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.4
  1953: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.18
  2136: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS GLIBC_2.2.5


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D47602