psyq-obj-parser: Handle comm symbols properly

Convert .comm symbols into the proper ELF equivalent, instead of
converting them to local symbol in the .bss segment.

This makes it possible use the converted PSY-Q libraries to recreate a
bit-exact executable of Frogger - without proper comm symbol support
controlling the order of some .bss symbols in the libraries is
impossible.

Even though this is more correct than before there is a chance some
users of psyq-obj-parser are relying on the old behaviour thus this
could be a breaking change for them. If so command line option could be
added to control between old and new behaviour.

Author: dezgeg

tools/psyq-obj-parser/psyq-obj-parser.cc

@@ -283,25 +283,6 @@ std::unique_ptr<PsyqLnkFile> PsyqLnkFile::parse(PCSX::IO<PCSX::File> file, bool
                         ret->symbolsList.push_back(&symbol);
                     }
                 }
-                // Determine bss symbol placement
-                // This has to be done after parsing the whole psyq object, as bss may be out of order in the file.
-                // Doing it here ensures that we process symbols in their id order, instead of by psyq object file
-                // order, if the user requested ordering by id - otherwise, it'll indeed be order of appearance.
-                for (auto& symbol : ret->symbolsList) {
-                    // Static bss symbols will be represented as a ZEROES opcode instead of UNINITIALIZED.
-                    // This will cause them to have a size of zero, so ignore size zero symbols here.
-                    // Their relocs will resolve to an offset of the local .bss instead, so this causes no issues.
-                    if (symbol.size > 0) {
-                        auto section = ret->sections.find(symbol.sectionIndex);
-                        if (section != ret->sections.end() && section->isBss()) {
-                            auto align = std::min((uint32_t)section->alignment, symbol.size) - 1;
-                            section->uninitializedOffset += align;
-                            section->uninitializedOffset &= ~align;
-                            symbol.offset = section->uninitializedOffset;
-                            section->uninitializedOffset += symbol.size;
-                        }
-                    }
-                }
                 return ret;
             }
             case (uint8_t)PsyqOpcode::BYTES: {
@@ -970,7 +951,9 @@ bool PsyqLnkFile::Symbol::generateElfSymbol(PsyqLnkFile* psyq, ELFIO::string_sec
     bool isWeak = false;
 
     fmt::print("    :: Generating symbol {} {} {}\n", name, getOffset(psyq), sectionIndex);
-    if (symbolType != Type::IMPORTED) {
+    if (symbolType == Type::UNINITIALIZED) {
+        elfSectionIndex = ELFIO::SHN_COMMON;
+    } else if (symbolType != Type::IMPORTED) {
         auto section = psyq->sections.find(sectionIndex);
         if (section == psyq->sections.end()) {
             psyq->setElfConversionError("Couldn't find section index {} for symbol {} ('{}')", sectionIndex, getKey(),
@@ -1387,7 +1370,8 @@ bool PsyqLnkFile::Relocation::generateElf(ElfRelocationPass pass, const std::str
                     psyq->setElfConversionError("Couldn't find symbol {} for relocation.", expr->symbolIndex);
                     return false;
                 }
-                if (symbol->symbolType != PsyqLnkFile::Symbol::Type::IMPORTED) {
+                if (symbol->symbolType != PsyqLnkFile::Symbol::Type::IMPORTED &&
+                    symbol->symbolType != PsyqLnkFile::Symbol::Type::UNINITIALIZED) {
                     return localSymbolReloc(symbol->sectionIndex, symbol->getOffset(psyq) + addend);
                 }
                 if (pass == ElfRelocationPass::PASS1) {