[PATCH] D108006: [lld][ELF] Add --no-search-static-libs-for-shlib-undefined flag

[Pirama Arumuga Nainar via Phabricator via llvm-commits]

pirama created this revision.
pirama added reviewers: peter.smith, MaskRay, srhines.
Herald added subscribers: dang, arichardson, emaste.
pirama requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This change addresses PR43554.

Android platform builds have two properties:

- Always build executables and libraries with -Wl,--no-undefined
- Several util libraries linked as statically or as a shared object

across executables and libraries.

This flag will make ld.lld not open static libraries to provide
undefined symbols from a shared library.  In Android, those symbols are
guaranteed to be available at runtime (because of -Wl,--no-undefined).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108006

Files:
  lld/ELF/Config.h
  lld/ELF/Driver.cpp
  lld/ELF/Options.td
  lld/ELF/Symbols.cpp


Index: lld/ELF/Symbols.cpp
===================================================================
--- lld/ELF/Symbols.cpp
+++ lld/ELF/Symbols.cpp
@@ -479,6 +479,10 @@
       return;
     }
 
+    if (other.file && dyn_cast<SharedFile>(other.file) &&
+        !config->searchStaticLibForShlibUndefined)
+      return;
+
     // Do extra check for --warn-backrefs.
     //
     // --warn-backrefs is an option to prevent an undefined reference from
Index: lld/ELF/Options.td
===================================================================
--- lld/ELF/Options.td
+++ lld/ELF/Options.td
@@ -298,6 +298,9 @@
 def no_omagic: F<"no-omagic">, MetaVarName<"<magic>">,
   HelpText<"Do not set the text data sections to be writable, page align sections (default)">;
 
+def no_search_static_libs_for_shlib_undefined: F<"no-search-static-libs-for-shlib-undefined">,
+  HelpText<"Do not search static libraries for undefined symbols in shared libraries">;
+
 def no_undefined: F<"no-undefined">,
   HelpText<"Report unresolved symbols even if the linker is creating a shared library">;
 
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -1099,6 +1099,8 @@
       args.hasFlag(OPT_mmap_output_file, OPT_no_mmap_output_file, true);
   config->nmagic = args.hasFlag(OPT_nmagic, OPT_no_nmagic, false);
   config->noinhibitExec = args.hasArg(OPT_noinhibit_exec);
+  config->searchStaticLibForShlibUndefined =
+      !args.hasArg(OPT_no_search_static_libs_for_shlib_undefined, false);
   config->nostdlib = args.hasArg(OPT_nostdlib);
   config->oFormatBinary = isOutputFormatBinary(args);
   config->omagic = args.hasFlag(OPT_omagic, OPT_no_omagic, false);
Index: lld/ELF/Config.h
===================================================================
--- lld/ELF/Config.h
+++ lld/ELF/Config.h
@@ -211,6 +211,7 @@
   bool symbolic;
   bool isStatic = false;
   bool sysvHash = false;
+  bool searchStaticLibForShlibUndefined = true;
   bool target1Rel;
   bool trace;
   bool thinLTOEmitImportsFiles;


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