Remove unnecessary includes from lld/ELF

[yamaguchi]

Summary

These includes are already included in somewhere above the include tree, so we don't have to include them here.

[dblaikie]

Generally, relying on indirect inclusion isn't ideal - if the intermediate headers are later refactored & remove the includes, it may break the build of those depending on that indirect inclusion.

Was there a particular motivation for these changes?

[• espindola]

Some of these seem to be really unused (mutex in InputSection.cpp).

Ideally we would remove just those. Given that this changes just cpp files, I am somewhat tempted to LGTM this. If we want to avoid indirect includes, how dependable is IWYU these days? Would the bots doing module builds find any problems?

[ruiu]

When I'm writing code for lld, I'm trying to maintain the include file list so that a .cpp file includes everything that the file uses, as indirect file inclusion feels somewhat fragile and not explicit. Because I'm doing that by hand, I'm pretty sure that we miss a lot of header files, but the spirit is to make the include list more explicit than implicit (and making things explicit and obvious is probably more "lld-ish", I would say). So I'm included to not do this.

Maybe you now have a question as to why we don't enforce it by a tool then? I think if everybody agrees that we should use a tool and always include what you use, that's fine, but I personally don't have enough motivation to propose that. In addition to that, it is in practice hard to ask everyone (including one-time contributors) to use some tool. So status quo is ok to me. Thank you for your patch anyways!

lld/ELF/Driver.cpp

 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/TarWriter.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstdlib>
-#include <utility>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::sys;
 
 using namespace lld;
 using namespace lld::elf;

lld/ELF/InputSection.cpp

 #include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Memory.h"
 #include "llvm/Object/Decompressor.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/Threading.h"
 #include "llvm/Support/xxhash.h"
-#include <mutex>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::support;
 using namespace llvm::support::endian;
 using namespace llvm::sys;
 

lld/ELF/LTO.cpp

 #include "llvm/LTO/Config.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
-#include <algorithm>
-#include <cstddef>
-#include <memory>
-#include <string>
-#include <system_error>
-#include <vector>
 
 using namespace llvm;
 using namespace llvm::object;
 using namespace llvm::ELF;
 
 using namespace lld;
 using namespace lld::elf;
 

lld/ELF/LinkerScript.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
-#include <algorithm>
-#include <cassert>
-#include <cstddef>
-#include <cstdint>
-#include <iterator>
-#include <limits>
-#include <string>
 #include <vector>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::support::endian;
 using namespace lld;
 using namespace lld::elf;

lld/ELF/MarkLive.cpp

 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "Target.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Strings.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Object/ELF.h"
 #include <functional>
-#include <vector>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::support::endian;
 
 using namespace lld;
 using namespace lld::elf;

lld/ELF/ScriptParser.cpp

 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include <cassert>
 #include <limits>
-#include <vector>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::support::endian;
 using namespace lld;
 using namespace lld::elf;
 
 static bool isUnderSysroot(StringRef Path);

lld/ELF/Thunks.cpp

 #include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Memory.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
 #include <cstdint>
-#include <cstring>
 
 using namespace llvm;
 using namespace llvm::object;
 using namespace llvm::ELF;
 
 namespace lld {
 namespace elf {