[WebAssembly] Remove used --sysroot option

[sbc100]

• remove from .td file

[sunfish]

Sysroot is a useful feature on other platforms. What is the reason for removing it, rather than implementing it :-)?

[sbc100]

I'm not removing --sysroot from the toolchain (i.e. clang and the driver), only from lld. In lld only the ELF driver supports sysroot and the only thing is provides is that ability for the user to pass special -L flag with = at the start. i.e. -L=/path/in/sysroot. Do you think this is useful feature? Normally the sysroot library paths are constructed by clang based on the --sysroot you pass to it, and are fully expanded by the time the linker sees them.

[sbc100]

It allows one to write:

lld --sysroot=/foo -L=/usr/lib -L=/usr/local/lib

as shorthand for:

lld -L/foo/usr/lib -L/foo/usr/local/lib

(although in this case is actually shorter to write the latter).

I've need seen this used in practice and its not used by the clang driver.

[sbc100]

I would argue that we can always add this feature if the future, but implementing now seems unnecessary.

[sunfish]

Ok, cool. Yeah, I was mainly thinking about --sysroot in clang.

[ruiu]

I'm happy to see it's gone. LGTM

wasm/Config.h

struct Configuration {
   bool StripAll;
   bool StripDebug;
   uint32_t GlobalBase;
   uint32_t InitialMemory;
   uint32_t MaxMemory;
   uint32_t ZStackSize;
   llvm::StringRef Entry;
   llvm::StringRef OutputFile;
-  llvm::StringRef Sysroot;
 
   llvm::StringSet<> AllowUndefinedSymbols;
   std::vector<llvm::StringRef> SearchPaths;
   std::vector<std::pair<Symbol *, WasmGlobal>> SyntheticGlobals;
 };
 
 // The only instance of Configuration struct.
 extern Configuration *Config;
 
 } // namespace wasm
 } // namespace lld
 
 #endif

wasm/Driver.cpp

void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
   Config->Entry = Args.getLastArgValue(OPT_entry);
   Config->ImportMemory = Args.hasArg(OPT_import_memory);
   Config->OutputFile = Args.getLastArgValue(OPT_o);
   Config->Relocatable = Args.hasArg(OPT_relocatable);
   Config->SearchPaths = args::getStrings(Args, OPT_L);
   Config->StripAll = Args.hasArg(OPT_strip_all);
   Config->StripDebug = Args.hasArg(OPT_strip_debug);
-  Config->Sysroot = Args.getLastArgValue(OPT_sysroot);
   errorHandler().Verbose = Args.hasArg(OPT_verbose);
   ThreadsEnabled = Args.hasFlag(OPT_threads, OPT_no_threads, true);
 
   Config->InitialMemory = args::getInteger(Args, OPT_initial_memory, 0);
   Config->GlobalBase = args::getInteger(Args, OPT_global_base, 1024);
   Config->MaxMemory = args::getInteger(Args, OPT_max_memory, 0);
   Config->ZStackSize =
       args::getZOptionValue(Args, OPT_z, "stack-size", WasmPageSize);

wasm/Options.td

 def relocatable: F<"relocatable">, HelpText<"Create relocatable object file">;
 
 def emit_relocs: F<"emit-relocs">, HelpText<"Generate relocations in output">;
 
 def strip_all: F<"strip-all">, HelpText<"Strip all symbols">;
 
 def strip_debug: F<"strip-debug">, HelpText<"Strip debugging information">;
 
-def sysroot: J<"sysroot=">, HelpText<"Set the system root">;
-
 def z: JoinedOrSeparate<["-"], "z">, MetaVarName<"<option>">,
   HelpText<"Linker option extensions">;
 
 def entry: S<"entry">, MetaVarName<"<entry>">,
   HelpText<"Name of entry point symbol">;
 
 def error_limit: J<"error-limit=">,
   HelpText<"Maximum number of errors to emit before stopping (0 = no limit)">;