[MachO] Fix incorrect handling of BIND_SPECIAL_DYLIB_*_LOOKUP in chained fixups

These lookup modes are negative values that are encoded in the library
ordinal, an unsigned field, of an import fixup entry. Incorrect sign
extension when converting these ordinals back to signed values led
to them being misinterpreted.

Author: bdash

view/macho/chained_fixups.cpp

@@ -247,7 +247,7 @@ ImportEntry ReadChainedImport32(BinaryReader& reader, std::span<const char> symb
 	return {
 		std::string_view(&symbolData[import.name_offset]),
 		0,
-		static_cast<int32_t>(import.lib_ordinal),
+		static_cast<int8_t>(import.lib_ordinal),
 		(bool)import.weak_import,
 	};
 }
@@ -259,7 +259,7 @@ ImportEntry ReadChainedImportAddend32(BinaryReader& reader, std::span<const char
 	return {
 		std::string_view(&symbolData[import.name_offset]),
 		static_cast<uint32_t>(import.addend),
-		static_cast<int32_t>(import.lib_ordinal),
+		static_cast<int8_t>(import.lib_ordinal),
 		(bool)import.weak_import,
 	};
 }
@@ -271,7 +271,7 @@ ImportEntry ReadChainedImportAddend64(BinaryReader& reader, std::span<const char
 	return {
 		std::string_view(&symbolData[import.name_offset]),
 		import.addend,
-		static_cast<int32_t>(import.lib_ordinal),
+		static_cast<int16_t>(import.lib_ordinal),
 		(bool)import.weak_import,
 	};
 }