Fix sorting in symbol_table_baset::show

This is a fix for 25ffad4; std::string::compare returns an integer <0,
==0 or >0, but std::sort wants a boolean when <0.

Now use a shared sorting implementation, which also makes sure we test
this in various regression tests.

Author: Daniel Kroening

src/goto-programs/show_symbol_table.cpp

@@ -70,17 +70,10 @@ void show_symbol_table_plain(
 {
   out << '\n' << "Symbols:" << '\n' << '\n';
 
-  // we want to sort alphabetically
-  std::vector<std::string> symbols;
-  symbols.reserve(symbol_table.symbols.size());
-
-  for(const auto &symbol_pair : symbol_table.symbols)
-    symbols.push_back(id2string(symbol_pair.first));
-  std::sort(symbols.begin(), symbols.end());
-
   const namespacet ns(symbol_table);
 
-  for(const irep_idt &id : symbols)
+  // we want to sort alphabetically
+  for(const irep_idt &id : symbol_table.sorted_symbol_names())
   {
     const symbolt &symbol=ns.lookup(id);
 

src/util/symbol_table_base.cpp

@@ -33,22 +33,30 @@ bool symbol_table_baset::remove(const irep_idt &name)
   return false;
 }
 
-/// Print the contents of the symbol table.
-/// \param out: The ostream to direct output to.
-void symbol_table_baset::show(std::ostream &out) const
+std::vector<irep_idt> symbol_table_baset::sorted_symbol_names() const
 {
   std::vector<irep_idt> sorted_names;
   sorted_names.reserve(symbols.size());
+
   for(const auto &elem : symbols)
     sorted_names.push_back(elem.first);
+
   std::sort(
     sorted_names.begin(),
     sorted_names.end(),
-    [](const irep_idt &a, const irep_idt &b) { return a.compare(b); });
+    [](const irep_idt &a, const irep_idt &b) { return a.compare(b) < 0; });
+
+  return sorted_names;
+}
+
+/// Print the contents of the symbol table.
+/// \param out: The ostream to direct output to.
+void symbol_table_baset::show(std::ostream &out) const
+{
   out << "\n"
       << "Symbols:"
       << "\n";
-  for(const auto &name : sorted_names)
+  for(const auto &name : sorted_symbol_names())
     out << symbols.at(name);
 }
 

src/util/symbol_table_base.h

@@ -136,6 +136,10 @@ class symbol_table_baset
 
   void show(std::ostream &out) const;
 
+  /// Build and return a lexicographically sorted vector of symbol names from
+  /// all symbols stored in this symbol table.
+  std::vector<irep_idt> sorted_symbol_names() const;
+
   class iteratort
   {
   private: