line number for files with no newline

The parser sets the line number used for error messages once reaching a
newline.  This fixes the logic for the case that the input file does not
have a newline.

This is only visible on .i files, as the preprocessor adds a newline when
there isn't one on .c files.

regression/ansi-c/errors/file_with_no_newline.desc

@@ -0,0 +1,7 @@
+CORE
+file_with_no_newline.i
+
+^file file_with_no_newline\.i line 1 function syntax: .*$
+^EXIT=6$
+^SIGNAL=0$
+--

regression/ansi-c/errors/file_with_no_newline.i

@@ -0,0 +1 @@
+syntax error, no newline here ->

src/ansi-c/ansi_c_parser.cpp

@@ -208,13 +208,13 @@ void ansi_c_parsert::set_pragma_cprover()
     for(const auto &pragma : pragma_set)
       flattened[pragma.first] = pragma.second;
 
-  source_location.remove(ID_pragma);
+  _source_location.remove(ID_pragma);
 
   for(const auto &pragma : flattened)
   {
     std::string check_name = id2string(pragma.first);
     std::string full_name =
       (pragma.second ? "enable:" : "disable:") + check_name;
-    source_location.add_pragma(full_name);
+    _source_location.add_pragma(full_name);
   }
 }

src/cpp/cpp_parser.h

@@ -56,7 +56,7 @@ class cpp_parsert:public parsert
   void add_location()
   {
     token_buffer.current_token().line_no=get_line_no()-1;
-    token_buffer.current_token().filename=source_location.get_file();
+    token_buffer.current_token().filename = source_location().get_file();
   }
 
   // scanner

src/util/parser.cpp

@@ -40,7 +40,7 @@ void parsert::parse_error(
   tmp_source_location.set_column(column-before.size());
   print(1, tmp, -1, tmp_source_location);
 #else
-  log.error().source_location = source_location;
+  log.error().source_location = source_location();
   log.error() << tmp << messaget::eom;
 #endif
 }

src/util/parser.h

@@ -17,6 +17,7 @@ Author: Daniel Kroening, [email protected]
 
 #include <filesystem>
 #include <iosfwd>
+#include <limits>
 #include <string>
 #include <vector>
 
@@ -33,7 +34,7 @@ class parsert
     : in(nullptr),
       log(message_handler),
       line_no(0),
-      previous_line_no(0),
+      previous_line_no(std::numeric_limits<unsigned int>::max()),
       column(1)
   {
   }
@@ -82,14 +83,14 @@ class parsert
 
   void set_file(const irep_idt &file)
   {
-    source_location.set_file(file);
-    source_location.set_working_directory(
+    _source_location.set_file(file);
+    _source_location.set_working_directory(
       std::filesystem::current_path().string());
   }
 
   irep_idt get_file() const
   {
-    return source_location.get_file();
+    return _source_location.get_file();
   }
 
   unsigned get_line_no() const
@@ -107,21 +108,31 @@ class parsert
     column=_column;
   }
 
-  void set_source_location(exprt &e)
+  const source_locationt &source_location()
   {
     // Only set line number when needed, as this destroys sharing.
     if(previous_line_no!=line_no)
     {
       previous_line_no=line_no;
-      source_location.set_line(line_no);
+
+      // for the case of a file with no newlines
+      if(line_no == 0)
+        _source_location.set_line(1);
+      else
+        _source_location.set_line(line_no);
     }
 
-    e.add_source_location()=source_location;
+    return _source_location;
+  }
+
+  void set_source_location(exprt &e)
+  {
+    e.add_source_location() = source_location();
   }
 
   void set_function(const irep_idt &function)
   {
-    source_location.set_function(function);
+    _source_location.set_function(function);
   }
 
   void advance_column(unsigned token_width)
@@ -131,7 +142,7 @@ class parsert
 
 protected:
   messaget log;
-  source_locationt source_location;
+  source_locationt _source_location;
   unsigned line_no, previous_line_no;
   unsigned column;
 };