Warn when --version-script has no effect

include/eld/Diagnostics/DiagLDScript.inc

@@ -65,6 +65,12 @@ DIAG(reading_dynamic_list, DiagnosticEngine::Verbose, "Dynamic List[%0] : %1")
 DIAG(reading_extern_list, DiagnosticEngine::Verbose, "Extern List[%0] : %1")
 DIAG(error_parsing_version_script, DiagnosticEngine::Error,
      "Error parsing version script %0")
+DIAG(warn_version_script_no_dynsym, DiagnosticEngine::Warning,
+     "%0: warning: version script has no effect: static executable does not "
+     "emit a dynamic symbol table")
+DIAG(warn_version_script_no_effect_relocatable, DiagnosticEngine::Warning,
+     "%0: warning: version script has no effect: relocatable output (-r) does "
+     "not emit a dynamic symbol table")
 DIAG(fatal_divide_by_zero, DiagnosticEngine::Fatal,
      "%0: division by zero in expression %1")
 DIAG(fatal_modulo_by_zero, DiagnosticEngine::Fatal,

lib/Object/ObjectLinker.cpp

@@ -367,6 +367,18 @@ bool ObjectLinker::parseVersionScript() {
     // Record the dynamic list script in the Map file.
     if (layoutInfo)
       layoutInfo->recordVersionScript(List);
+    // Warn if the version script will have no effect because no dynamic
+    // symbol table will be emitted.
+    if (ThisConfig.isLinkPartial()) {
+      // Relocatable output (-r) never emits .dynsym.
+      ThisConfig.raise(Diag::warn_version_script_no_effect_relocatable)
+          << VersionScriptInput->decoratedPath();
+    } else if (ThisConfig.isCodeStatic() && !ThisConfig.options().isPIE() &&
+               !ThisConfig.options().forceDynamic()) {
+      // Static executable without PIE or --force-dynamic doesn't emit .dynsym.
+      ThisConfig.raise(Diag::warn_version_script_no_dynsym)
+          << VersionScriptInput->decoratedPath();
+    }
     // Read the dynamic List file
     ScriptFile VersionScriptReader(
         ScriptFile::VersionScript, *ThisModule,

test/Common/standalone/VersionScript/VersionScriptNoEffect.test

@@ -0,0 +1,34 @@
+# Test that version scripts emit warnings when they have no effect
+# (i.e., when no dynamic symbol table will be created)
+
+# RUN 1: Static executable should warn
+RUN: %clang %clangopts -c -O2 %p/Inputs/1.c -o %t1.o
+RUN: %link %linkopts -static --entry=main --version-script=%p/Inputs/vs1 -o %t_static.out %t1.o 2>&1 | %filecheck --check-prefix=WARN-STATIC %s
+
+WARN-STATIC: warning: version script has no effect: static executable does not emit a dynamic symbol table
+
+# RUN 2: Relocatable output should warn
+RUN: %link %linkopts -r --version-script=%p/Inputs/vs1 -o %t_reloc.o %t1.o 2>&1 | %filecheck --check-prefix=WARN-RELOC %s
+
+WARN-RELOC: warning: version script has no effect: relocatable output (-r) does not emit a dynamic symbol table
+
+# RUN 3: PIE executable should NOT warn (has .dynsym)
+RUN: %clang %clangopts -c -fpic -O2 %p/Inputs/1.c -o %t1_pic.o
+RUN: %link %linkopts -pie --entry=main --version-script=%p/Inputs/vs1 -o %t_pie.out %t1_pic.o 2>&1 | %filecheck --allow-empty --check-prefix=NO-WARN-PIE %s
+
+NO-WARN-PIE-NOT: warning: version script has no effect
+
+# RUN 4: Shared library should NOT warn (has .dynsym)
+RUN: %link %linkopts -shared --version-script=%p/Inputs/vs1 -o %t_shared.so %t1_pic.o 2>&1 | %filecheck --allow-empty --check-prefix=NO-WARN-SHARED %s
+
+NO-WARN-SHARED-NOT: warning: version script has no effect
+
+# RUN 5: Static with --force-dynamic should NOT warn (forces .dynsym)
+RUN: %link %linkopts -static --force-dynamic --entry=main --version-script=%p/Inputs/vs1 -o %t_force.out %t1.o 2>&1 | %filecheck --allow-empty --check-prefix=NO-WARN-FORCE %s
+
+NO-WARN-FORCE-NOT: warning: version script has no effect
+
+# RUN 6: Verify the warnings include the version script path
+RUN: %link %linkopts -static --entry=main --version-script=%p/Inputs/vs1 -o %t_path.out %t1.o 2>&1 | %filecheck --check-prefix=CHECK-PATH %s
+
+CHECK-PATH: {{.*}}/Inputs/vs1: warning: version script has no effect