goto-cc: show error line

regression/ansi-c/const1/const-array.desc

@@ -1,6 +1,7 @@
 CORE
 const-array.c
  ^.*: .* is constant$
+^   array\[1\] = 2;$
 ^EXIT=(1|64)$
 ^SIGNAL=0$
 --

regression/ansi-c/const1/const-member.desc

@@ -2,6 +2,7 @@ CORE
 const-member.c
 
 ^.*: .* is constant$
+^   const_struct_ptr->field = 123;$
 ^EXIT=(1|64)$
 ^SIGNAL=0$
 --

src/util/cout_message.cpp

@@ -8,6 +8,7 @@ Author: Daniel Kroening, [email protected]
 
 #include "cout_message.h"
 
+#include <fstream>
 #include <iostream>
 
 #ifdef _WIN32
@@ -185,6 +186,26 @@ void gcc_message_handlert::print(
   dest+=message;
 
   print(level, dest);
+
+  const auto file_name = location.full_path();
+  if(file_name.has_value() && !line.empty())
+  {
+#ifdef _WIN32
+    std::ifstream in(widen(file_name.value()));
+#else
+    std::ifstream in(file_name.value());
+#endif
+    if(in)
+    {
+      const auto line_number = std::stoull(id2string(line));
+      std::string line;
+      for(std::size_t l = 0; l < line_number; l++)
+        std::getline(in, line);
+
+      if(in)
+        print(level, " " + line); // gcc adds a space, clang doesn't
+    }
+  }
 }
 
 void gcc_message_handlert::print(

src/util/source_location.cpp

@@ -71,6 +71,19 @@ void source_locationt::merge(const source_locationt &from)
   }
 }
 
+/// Get a path to the file, including working directory.
+/// \return Full path unless the file name is empty or refers
+/// to a built-in, in which case {} is returned.
+optionalt<std::string> source_locationt::full_path() const
+{
+  const auto file = id2string(get_file());
+
+  if(file.empty() || is_built_in(file))
+    return {};
+
+  return concat_dir_file(id2string(get_working_directory()), file);
+}
+
 std::ostream &operator << (
   std::ostream &out,
   const source_locationt &source_location)

src/util/source_location.h

@@ -12,6 +12,7 @@ Author: Daniel Kroening, [email protected]
 
 #include "invariant.h"
 #include "irep.h"
+#include "optional.h"
 #include "prefix.h"
 
 #include <string>
@@ -185,6 +186,8 @@ class source_locationt:public irept
     return static_cast<const source_locationt &>(get_nil_irep());
   }
 
+  optionalt<std::string> full_path() const;
+
 protected:
   std::string as_string(bool print_cwd) const;
 };