[Lldb-commits] [PATCH] D67390: [LLDB][ELF] Load both, .symtab and .dynsym sections

Konrad Wilhelm Kleine via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Thu Sep 26 21:03:37 PDT 2019

kwk added a comment.

Not all is answered now but please respect: https://reviews.llvm.org/D67390#1683705

Comment at: lldb/source/Plugins/ObjectFile/ELF/ELFHeader.cpp:371-373
+  r.st_name = st_name;
+  return elf::ELFSymbol::operator==(r) &&
+         st_name_string == rhs.st_name_string;
clayborg wrote:
> I would almost just manually compare only the things we care about here. Again, what about st_shndx when comparing a symbol from the main symbol table and one from the .gnu_debugdata symbol table. Are those section indexes guaranteed to match? I would think not. 
@clayborg I explicitly only compare what we care about and therefore always set the name index to  be the same.

Comment at: lldb/source/Plugins/ObjectFile/ELF/ELFHeader.h:289
+struct NamedELFSymbol : ELFSymbol {
+  lldb_private::ConstString st_name_string; ///< Actual name of the ELF symbol
clayborg wrote:
> Do we need a ConstString for the st_shndx as well so we can correctly compare a section from one file to a section from another as in the .gnu_debugdata case?
That is a good point.

Comment at: lldb/source/Plugins/ObjectFile/ELF/ELFHeader.h:440
+    tmp.st_name = 0;
+    std::size_t h1 = std::hash<elf::ELFSymbol>()(tmp);
+    std::size_t h2 = std::hash<const char *>()(s.st_name_string.AsCString());
clayborg wrote:
> Don't we need to hash everything we care about except the st_name? Those indexes can differ if they come from a different string table? Shouldn't this be:
> ```
> std::size_t h1 = std::hash<elf::elf_addr>()(s.st_value);
> std::size_t h2 = std::hash<elf::elf_xword>()(s.st_size);
> // Skip std::size_t h3 = std::hash<elf::elf_word>()(s.st_name);
> std::size_t h4 = std::hash<unsigned char>()(s.st_info);
> std::size_t h5 = std::hash<unsigned char>()(s.st_other);
> std::size_t h6 = std::hash<elf::elf_half>()(s.st_shndx);
> std::size_t h7 = std::hash<const char *>()(s.st_name_string.AsCString());
> return llvm::hash_combine(h1, h2, h4, h5, h6, h7);
> ```
> I left the "h" variables with the same names to show we don't want "h3".
That's why I explicitly set the name to 0 always which effectively ignores it because it has no effect on the hash then. Please see the specialization hash for `NamedELFSymbol`.

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