[PATCH] D64130: [LLD][ELF] - Linkerscript: add a support for expressions for section's filling

[Peter Smith via Phabricator via llvm-commits]

peter.smith added a comment.

It looks like gold and bfd disagree on whether a symbol is allowed in practice.

  foo = 0x12345678;
  
  SECTIONS {
   .text : { *(.text) } = foo
  }

With ld.bfd I get an error, even if I use ABSOLUTE(foo)

  ld.bfd fill.o -T fill.lds
  fill.lds:4: nonconstant expression for fill value

With gold the link succeeds

  ld.gold fill.o -T fill.lds

The ld.bfd I used was quite old 2.26.1 so this may have changed in later versions. Trying a later version lead to a ld.bfd segfault in one case.

As I think that this is an improvement and I agree that a symbol is unlikely to be encountered in practice so I think this is worth doing.



================
Comment at: ELF/ScriptParser.cpp:884
 // We are compatible with ld.gold because it's easier to implement.
-std::array<uint8_t, 4> ScriptParser::parseFill(StringRef Tok) {
-  uint32_t V = 0;
-  if (!to_integer(Tok, V))
-    setError("invalid filler expression: " + Tok);
+std::array<uint8_t, 4> ScriptParser::readFill() {
+  uint64_t Value = readExpr()().Val;
----------------
It is worth a comment or FIXME: saying we don't support symbols in fill expressions?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64130/new/

https://reviews.llvm.org/D64130