Add --warn-unresolved-symbols and --error-unresolved-symbols

arch_i386.cc

@@ -258,7 +258,7 @@ void InputSection<I386>::apply_reloc_nonalloc(Context<I386> &ctx, u8 *base) {
     u8 *loc = base + rel.r_offset;
 
     if (!sym.file) {
-      Error(ctx) << "undefined symbol: " << file << ": " << sym;
+      report_undef(ctx, sym);
       continue;
     }
 
@@ -322,7 +322,7 @@ void InputSection<I386>::scan_relocations(Context<I386> &ctx) {
     u8 *loc = (u8 *)(contents.data() + rel.r_offset);
 
     if (!sym.file) {
-      Error(ctx) << "undefined symbol: " << file << ": " << sym;
+      report_undef(ctx, sym);
       continue;
     }
 

arch_x86_64.cc

@@ -427,7 +427,7 @@ void InputSection<X86_64>::apply_reloc_nonalloc(Context<X86_64> &ctx, u8 *base)
     u8 *loc = base + rel.r_offset;
 
     if (!sym.file) {
-      Error(ctx) << "undefined symbol: " << file << ": " << sym;
+      report_undef(ctx, sym);
       continue;
     }
 
@@ -495,7 +495,7 @@ void InputSection<X86_64>::scan_relocations(Context<X86_64> &ctx) {
     u8 *loc = (u8 *)(contents.data() + rel.r_offset);
 
     if (!sym.file) {
-      Error(ctx) << "undefined symbol: " << file << ": " << sym;
+      report_undef(ctx, sym);
       continue;
     }
 

cmdline.cc

@@ -114,6 +114,9 @@ Options:
   --version-script FILE       Read version script
   --warn-common               Warn about common symbols
     --no-warn-common
+  --warn-unresolved-symbols   Report unresolved symbols as warnings
+    --error-unresolved-symbols
+                              Report unresolved symbols as errors (default)
   --whole-archive             Include all objects from static archives
     --no-whole-archive
   --wrap SYMBOL               Use wrapper function for a given symbol
@@ -644,7 +647,11 @@ void parse_nonpositional_args(Context<E> &ctx,
     } else if (read_flag(args, "strip-all") || read_flag(args, "s")) {
       ctx.arg.strip_all = true;
     } else if (read_flag(args, "strip-debug") || read_flag(args, "S")) {
-      ctx.arg.strip_debug = true;
+      ctx.arg.strip_all = true;
+    } else if (read_flag(args, "warn-unresolved-symbols")) {
+      ctx.arg.warn_unresolved_symbols = true;
+    } else if (read_flag(args, "error-unresolved-symbols")) {
+      ctx.arg.warn_unresolved_symbols = false;
     } else if (read_arg(ctx, args, arg, "rpath")) {
       if (!ctx.arg.rpaths.empty())
         ctx.arg.rpaths += ":";

input_sections.cc

@@ -100,5 +100,13 @@ void InputSection<E>::dispatch(Context<E> &ctx, Action table[3][4],
              << "' can not be used; recompile with -fPIE";
 }
 
+template <typename E>
+void InputSection<E>::report_undef(Context<E> &ctx, Symbol<E> &sym) {
+  if (ctx.arg.warn_unresolved_symbols)
+    Warn(ctx) << "undefined symbol: " << file << ": " << sym;
+  else
+    Error(ctx) << "undefined symbol: " << file << ": " << sym;
+}
+
 template class InputSection<X86_64>;
 template class InputSection<I386>;

main.cc

@@ -441,7 +441,7 @@ int do_main(int argc, char **argv) {
   // If we are linking a .so file, remaining undefined symbols does
   // not cause a linker error. Instead, they are treated as if they
   // were imported symbols.
-  if (ctx.arg.shared && !ctx.arg.z_defs) {
+  if ((ctx.arg.shared && !ctx.arg.z_defs) || ctx.arg.warn_unresolved_symbols) {
     Timer t(ctx, "claim_unresolved_symbols");
     tbb::parallel_for_each(ctx.objs, [](ObjectFile<E> *file) {
       file->claim_unresolved_symbols();

mold.h

@@ -262,7 +262,6 @@ public:
   }
 
   void scan_relocations(Context<E> &ctx);
-  void report_undefined_symbols();
   void write_to(Context<E> &ctx, u8 *buf);
   void apply_reloc_alloc(Context<E> &ctx, u8 *base);
   void apply_reloc_nonalloc(Context<E> &ctx, u8 *base);
@@ -319,6 +318,7 @@ private:
   void do_uncompress(Context<E> &ctx, std::string_view data, u64 size);
 
   void dispatch(Context<E> &ctx, Action table[3][4], u16 rel_type, i64 i);
+  void report_undef(Context<E> &ctx, Symbol<E> &sym);
 };
 
 //
@@ -1450,6 +1450,7 @@ struct Context {
     bool strip_debug = false;
     bool trace = false;
     bool warn_common = false;
+    bool warn_unresolved_symbols = false;
     bool z_copyreloc = true;
     bool z_defs = false;
     bool z_delete = true;

test/warn-unresolved-symbols.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -e
+cd $(dirname $0)
+echo -n "Testing $(basename -s .sh $0) ... "
+t=$(pwd)/tmp/$(basename -s .sh $0)
+mkdir -p $t
+
+cat <<EOF | clang -c -o $t/a.o -xc -
+int foo();
+int main() {
+  foo();
+}
+EOF
+
+! clang -fuse-ld=`pwd`/../mold -o $t/exe $t/a.o 2>&1 \
+  | grep -q 'undefined symbol:.*foo'
+
+clang -fuse-ld=`pwd`/../mold -o $t/exe $t/a.o --warn-unresolved-symbols 2>&1 \
+  | grep -q 'undefined symbol:.*foo'
+
+! clang -fuse-ld=`pwd`/../mold -o $t/exe $t/a.o --warn-unresolved-symbols \
+  --error-unresolved-symbols 2>&1 \
+  | grep -q 'undefined symbol:.*foo'
+
+echo OK