[LLD][ELF] Extract temporary state used in assignAddresses()

[peter.smith]

Summary

The assignAddresses() function accumulates state in the LinkerScript that prevents it from being called multiple times. This change moves the state into a separate structure AddressState that is created at the start of the function and disposed of at the end.

CurAddressState is used rather than passing a reference to the state as a parameter to the functions used by assignAddresses(). This is because the getSymbolValue function needs to be executed in the context of AddressState but it is stored in ScriptParser when AddressState is not available.

The AddressState is also used in a limited context by processCommands()

[peter.smith]

This is patch 4/11 of range thunks although it can be applied independently.

[peter.smith]

I've updated to follow Rafael's suggestion to extract the state into a separate struct. The diff is mostly a replace Cur<State> with CurAddressState-><State>.

[mehdi_amini]

lld/trunk/ELF/LinkerScript.cpp

377 ↗

(On Diff #105598)

Coverity flags this as suspicious (and I agree):

>>>     CID 1377401:  Memory - illegal accesses  (WRAPPER_ESCAPE)
>>>     The internal representation of local "State" escapes into "this->CurAddressState", but is destroyed when it exits scope.

If this is intended, please add a comment.

[mehdi_amini]

lld/trunk/ELF/LinkerScript.cpp

846 ↗

(On Diff #105598)

Same here actually

ELF/LinkerScript.h

public:
   std::vector<PhdrEntry> createPhdrs();
   bool ignoreInterpSection();
 
   bool hasLMA(OutputSection *Sec);
   bool shouldKeep(InputSectionBase *S);
   void assignOffsets(OutputSectionCommand *Cmd);
   void createOrphanCommands();
   void processNonSectionCommands();
+  void resetAddressState();
   void assignAddresses();
   void allocateHeaders(std::vector<PhdrEntry> &Phdrs);
   void addSymbol(SymbolAssignment *Cmd);
   void processCommands(OutputSectionFactory &Factory);
 
   // Parsed linker script configurations are set to this struct.
   ScriptConfiguration Opt;
 };
 
 extern LinkerScript *Script;
 
 } // end namespace elf
 } // end namespace lld
 
 #endif // LLD_ELF_LINKER_SCRIPT_H

ELF/LinkerScript.cpp

void LinkerScript::allocateHeaders(std::vector<PhdrEntry> &Phdrs) {
   auto PhdrI = std::find_if(Phdrs.begin(), Phdrs.end(), [](const PhdrEntry &E) {
     return E.p_type == PT_PHDR;
   });
   if (PhdrI != Phdrs.end())
     Phdrs.erase(PhdrI);
   return;
 }
 
+// Reset the members associated with address assigment to their initial values
+// this permits addressAssignment to be run again.
+void LinkerScript::resetAddressState() {
+  LMAOffset = 0;
+  CurOutSec = nullptr;
+  CurMemRegion = nullptr;
+  ThreadBssOffset = 0;
+  for (auto &MRI : Opt.MemoryRegions) {
+    MemoryRegion &MR = MRI.second;
+    MR.Offset = MR.Origin;
+  }
+}
+
 void LinkerScript::assignAddresses() {
   // Assign addresses as instructed by linker script SECTIONS sub-commands.
   Dot = 0;
+  resetAddressState();
   ErrorOnMissingSection = true;
   switchTo(Aether);
 
   for (BaseCommand *Base : Opt.Commands) {
     if (auto *Cmd = dyn_cast<SymbolAssignment>(Base)) {
       assignSymbol(Cmd, false);
       continue;
     }