[PATCH] D81760: [WebAssembly] Add warnings for -shared and -pie

[Dan Gohman via Phabricator via llvm-commits]

sunfish created this revision.
Herald added subscribers: aheejin, jgravelle-google, sbc100, dschuff.
Herald added a project: LLVM.

The meaning of -shared and -pie are expected to be changed in the
future when Module Linking-style libraries are implemented. Begin
issuing warnings to give people a heads-up that they will be changing.

For compatibility with Emscripten, add a --emscripten-pic flag which
disables these warnings.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D81760

Files:
  lld/wasm/Config.h
  lld/wasm/Driver.cpp
  lld/wasm/Options.td


Index: lld/wasm/Options.td
===================================================================
--- lld/wasm/Options.td
+++ lld/wasm/Options.td
@@ -199,3 +199,7 @@
 defm thinlto_cache_policy: Eq<"thinlto-cache-policy", "Pruning policy for the ThinLTO cache">;
 def thinlto_jobs: J<"thinlto-jobs=">,
   HelpText<"Number of ThinLTO jobs. Default to --threads=">;
+
+// Emscripten PIC mode.
+def emscripten_pic: F<"emscripten-pic">,
+  HelpText<"Enable Emscripten-style PIC">;
Index: lld/wasm/Driver.cpp
===================================================================
--- lld/wasm/Driver.cpp
+++ lld/wasm/Driver.cpp
@@ -332,6 +332,7 @@
   config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
   config->disableVerify = args.hasArg(OPT_disable_verify);
   config->emitRelocs = args.hasArg(OPT_emit_relocs);
+  config->emscriptenPic = args.hasArg(OPT_emscripten_pic);
   config->entry = getEntry(args);
   config->exportAll = args.hasArg(OPT_export_all);
   config->exportTable = args.hasArg(OPT_export_table);
@@ -456,6 +457,23 @@
     if (config->sharedMemory)
       error("-r and --shared-memory may not be used together");
   }
+
+  // To begin to prepare for Module Linking-style shared libraries, start
+  // warning about uses of `-shared` and related flags outside of Emscripten
+  // mode, to give anyone using them a heads-up that they will be changing.
+  //
+  // Also, warn about flags which request explicit exports.
+  if (!config->emscriptenPic) {
+    // -shared will change meaning when Module Linking is implemented.
+    if (config->shared) {
+      warn("shared libraries are not yet implemented");
+    }
+
+    // -pie will change meaning when Module Linking is implemented.
+    if (config->pie) {
+      warn("PIE is not yet implemented");
+    }
+  }
 }
 
 // Force Sym to be entered in the output. Used for -u or equivalent.
Index: lld/wasm/Config.h
===================================================================
--- lld/wasm/Config.h
+++ lld/wasm/Config.h
@@ -27,6 +27,7 @@
   bool compressRelocations;
   bool demangle;
   bool disableVerify;
+  bool emscriptenPic;
   bool emitRelocs;
   bool exportAll;
   bool exportDynamic;


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