[ELF] LinkerScript: Don't assign zero to all regular symbols

This fixes an assertion `Align != 0u && "Align can't be 0."'
in llvm::alignTo() when a linker script references a globally
defined variable in an ALIGN() context.

Patch by Alexander Richardson !

Differential revision: https://reviews.llvm.org/D31984

llvm-svn: 300315

1 files changed, 6 insertions, 1 deletions

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index fdd6220c015..5a9e4652b22 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -68,8 +68,13 @@ template <class ELFT> static SymbolBody *addRegular(SymbolAssignment *Cmd) {
   Sym->Binding = STB_GLOBAL;
   ExprValue Value = Cmd->Expression();
   SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
+
+  // We want to set symbol values early if we can. This allows us to use symbols
+  // as variables in linker scripts. Doing so allows us to write expressions
+  // like this: `alignment = 16; . = ALIGN(., alignment)`
+  uint64_t SymValue = Value.isAbsolute() ? Value.getValue() : 0;
   replaceBody<DefinedRegular>(Sym, Cmd->Name, /*IsLocal=*/false, Visibility,
-                              STT_NOTYPE, 0, 0, Sec, nullptr);
+                              STT_NOTYPE, SymValue, 0, Sec, nullptr);
   return Sym->body();
 }