[ELF} Add --warn-once

rui314 · Feb 5, 2022 · f24b997 · f24b997
1 parent f72999a
commit f24b997
Show file tree

Hide file tree

Showing 9 changed files with 58 additions and 14 deletions.
diff --git a/elf/arch-arm64.cc b/elf/arch-arm64.cc
@@ -355,7 +355,7 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
     u8 *loc = base + rel.r_offset;
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 
@@ -400,7 +400,7 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
     Symbol<E> &sym = *file.symbols[rel.r_sym];
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 

diff --git a/elf/arch-i386.cc b/elf/arch-i386.cc
@@ -272,7 +272,7 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
     u8 *loc = base + rel.r_offset;
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 
@@ -369,7 +369,7 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
     Symbol<E> &sym = *file.symbols[rel.r_sym];
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 

diff --git a/elf/arch-riscv64.cc b/elf/arch-riscv64.cc
@@ -422,7 +422,7 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
     u8 *loc = base + rel.r_offset;
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 
@@ -544,7 +544,7 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
     Symbol<E> &sym = *file.symbols[rel.r_sym];
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 

diff --git a/elf/arch-x86-64.cc b/elf/arch-x86-64.cc
@@ -481,7 +481,7 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
     u8 *loc = base + rel.r_offset;
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 
@@ -580,7 +580,7 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
     u8 *loc = (u8 *)(contents.data() + rel.r_offset);
 
     if (!sym.file) {
-      report_undef(ctx, sym);
+      report_undef(ctx, file, sym);
       continue;
     }
 

diff --git a/elf/cmdline.cc b/elf/cmdline.cc
@@ -132,6 +132,7 @@ static const char helpmsg[] = R"(
   --version-script FILE       Read version script
   --warn-common               Warn about common symbols
     --no-warn-common
+  --warn-once                 Only warn once for each undefined symbol
   --warn-unresolved-symbols   Report unresolved symbols as warnings
     --error-unresolved-symbols
                               Report unresolved symbols as errors (default)
@@ -584,6 +585,8 @@ void parse_nonpositional_args(Context<E> &ctx,
       ctx.arg.warn_common = true;
     } else if (read_flag(args, "no-warn-common")) {
       ctx.arg.warn_common = false;
+    } else if (read_flag(args, "warn-once")) {
+      ctx.arg.warn_once = true;
     } else if (read_arg(ctx, args, arg, "compress-debug-sections")) {
       if (arg == "zlib" || arg == "zlib-gabi")
         ctx.arg.compress_debug_sections = COMPRESS_GABI;

diff --git a/elf/input-files.cc b/elf/input-files.cc
@@ -917,7 +917,7 @@ void ObjectFile<E>::claim_unresolved_symbols(Context<E> &ctx) {
     };
 
     if (ctx.arg.unresolved_symbols == UNRESOLVED_WARN)
-      Warn(ctx) << "undefined symbol: " << *this << ": " << sym;
+      report_undef(ctx, *this, sym);
 
     // Convert remaining undefined symbols to dynamic symbols.
     if (ctx.arg.shared) {

diff --git a/elf/input-sections.cc b/elf/input-sections.cc
@@ -200,7 +200,10 @@ void InputSection<E>::write_to(Context<E> &ctx, u8 *buf) {
 }
 
 template <typename E>
-void InputSection<E>::report_undef(Context<E> &ctx, Symbol<E> &sym) {
+void report_undef(Context<E> &ctx, InputFile<E> &file, Symbol<E> &sym) {
+  if (ctx.arg.warn_once && !ctx.warned.insert({(void *)&sym, 1}))
+    return;
+
   switch (ctx.arg.unresolved_symbols) {
   case UNRESOLVED_ERROR:
     Error(ctx) << "undefined symbol: " << file << ": " << sym;
@@ -213,9 +216,11 @@ void InputSection<E>::report_undef(Context<E> &ctx, Symbol<E> &sym) {
   }
 }
 
-#define INSTANTIATE(E)                          \
-  template struct CieRecord<E>;                 \
-  template class InputSection<E>;
+#define INSTANTIATE(E)                                                  \
+  template struct CieRecord<E>;                                         \
+  template class InputSection<E>;                                       \
+  template void report_undef(Context<E> &, InputFile<E> &, Symbol<E> &)
+
 
 INSTANTIATE(X86_64);
 INSTANTIATE(I386);

diff --git a/elf/mold.h b/elf/mold.h
@@ -326,7 +326,6 @@ class InputSection {
 
   void dispatch(Context<E> &ctx, Action table[3][4], i64 i,
                 const ElfRel<E> &rel, Symbol<E> &sym);
-  void report_undef(Context<E> &ctx, Symbol<E> &sym);
   void copy_contents(Context<E> &ctx, u8 *buf);
   void copy_contents_riscv(Context<E> &ctx, u8 *buf);
 
@@ -336,6 +335,9 @@ class InputSection {
   bool is_relr_reloc(Context<E> &ctx, const ElfRel<E> &rel);
 };
 
+template <typename E>
+void report_undef(Context<E> &ctx, InputFile<E> &file, Symbol<E> &sym);
+
 //
 // output-chunks.cc
 //
@@ -1432,6 +1434,7 @@ struct Context {
     bool strip_debug = false;
     bool trace = false;
     bool warn_common = false;
+    bool warn_once = false;
     bool z_copyreloc = true;
     bool z_defs = false;
     bool z_delete = true;
@@ -1535,6 +1538,9 @@ struct Context {
   std::atomic_bool has_gottp_rel = false;
   std::atomic_bool has_textrel = false;
 
+  // For --warn-once
+  tbb::concurrent_hash_map<void *, int> warned;
+
   // Output chunks
   std::unique_ptr<OutputEhdr<E>> ehdr;
   std::unique_ptr<OutputShdr<E>> shdr;

diff --git a/test/elf/warn-once.sh b/test/elf/warn-once.sh
@@ -0,0 +1,30 @@
+#!/bin/bash
+export LANG=
+set -e
+CC="${CC:-cc}"
+CXX="${CXX:-c++}"
+testname=$(basename "$0" .sh)
+echo -n "Testing $testname ... "
+cd "$(dirname "$0")"/../..
+mold="$(pwd)/mold"
+t=out/test/elf/$testname
+mkdir -p $t
+
+cat <<EOF | $CC -c -xc -o $t/a.o -
+extern int foo;
+int x() { return foo; }
+EOF
+
+cat <<EOF | $CC -c -xc -o $t/b.o -
+extern int foo;
+int y() { return foo; }
+int main() {}
+EOF
+
+$CC -B. -o $t/exe $t/a.o $t/b.o -Wl,--warn-unresolved-symbols >& $t/log1
+$CC -B. -o $t/exe $t/a.o $t/b.o -Wl,--warn-unresolved-symbols,--warn-once >& $t/log2
+
+[ "$(grep 'undefined symbol:.* foo$' $t/log1 | wc -l)" = 2 ]
+[ "$(grep 'undefined symbol:.* foo$' $t/log2 | wc -l)" = 1 ]
+
+echo OK