Merge pull request #7621 from karkhaz/kk-warn-on-undefined-symbol

Do not error on undefined external linker symbols

Author: tautschnig

src/goto-cc/linker_script_merge.cpp

@@ -727,17 +727,20 @@ int linker_script_merget::get_linker_script_data(
 }
 
 int linker_script_merget::goto_and_object_mismatch(
-    const std::list<irep_idt> &linker_defined_symbols,
-    const linker_valuest &linker_values)
+  const std::list<irep_idt> &linker_defined_symbols,
+  linker_valuest &linker_values)
 {
   int fail=0;
   for(const auto &sym : linker_defined_symbols)
     if(linker_values.find(sym)==linker_values.end())
     {
-      fail=1;
-      log.error() << "Variable '" << sym
-                  << "' was declared extern but never given "
-                  << "a value, even in a linker script" << messaget::eom;
+      log.warning() << "Variable '" << sym
+                    << "' was declared extern but never given a value, even in "
+                    << "a linker script" << messaget::eom;
+
+      null_pointer_exprt null_pointer(pointer_type(char_type()));
+      symbol_exprt null_sym(sym, pointer_type(char_type()));
+      linker_values.emplace(sym, std::make_pair(null_sym, null_pointer));
     }
 
   for(const auto &pair : linker_values)

src/goto-cc/linker_script_merge.h

@@ -197,8 +197,8 @@ class linker_script_merget
   /// \return `1` if there is some mismatch between the list and map, `0` if
   ///   everything is OK.
   int goto_and_object_mismatch(
-      const std::list<irep_idt> &linker_defined_symbols,
-      const linker_valuest &linker_values);
+    const std::list<irep_idt> &linker_defined_symbols,
+    linker_valuest &linker_values);
 
   /// \brief Validate output of the `scripts/ls_parse.py` tool
   int linker_data_is_malformed(const jsont &data) const;