Add multi-variable initialization ({$modeswitch multivarinit})

  var a, b, c: integer = 42;

Static vars use token record/replay so each gets its own typed
constant data. Local vars share a single `defaultconstsym`.
Enabled by default in unleashed mode.

Author: fibodevy

compiler/globals.pas

@@ -68,7 +68,8 @@ interface
           m_property,m_default_inline,m_except,m_multiline_strings];
        unleashedmodeswitches = objfpcmodeswitches+[m_default_ansistring,m_underscoreisseparator,m_duplicate_names,
         m_advanced_records,m_array_operators,m_anonymous_functions,m_function_references,
-        m_statement_expressions,m_array_equality,m_inline_var,m_multiline_strings];
+        m_statement_expressions,m_array_equality,m_inline_var,m_multiline_strings,
+        m_multi_var_init];
        tpmodeswitches =
          [m_tp7,m_tp_procvar,m_duplicate_names];
 {$ifdef gpc_mode}

compiler/globtype.pas

@@ -561,7 +561,8 @@        ttargetswitchinfo = record
          m_statement_expressions, { enables expressions using statements like if, case, try }
          m_array_equality,      { enables equality operator in addition to ArrayOperators modeswitch }
          m_no_rtti,             { hides RTTI ASCII text }
-         m_inline_var           { allow inline variable declarations inside statement blocks }
+         m_inline_var,          { allow inline variable declarations inside statement blocks }
+         m_multi_var_init       { allow initializing multiple variables in one declaration }
        );
        tmodeswitches = set of tmodeswitch;
 
@@ -773,7 +774,8 @@        ttargetswitchinfo = record
          'STATEMENTEXPRESSIONS',
          'ARRAYEQUALITY',
          'NORTTI',
-         'INLINEVARS'
+         'INLINEVARS',
+         'MULTIVARINIT'
          );
 
 

compiler/pdecvar.pas

@@ -1135,9 +1135,13 @@ implementation
           vs : tabstractnormalvarsym;
           tcsym : tstaticvarsym;
           templist : tasmlist;
+          i : longint;
+          tokenbuf : tdynamicarray;
+          already_recording : boolean;
         begin
           vs:=tabstractnormalvarsym(sc[0]);
-          if sc.count>1 then
+          if (sc.count>1) and
+             not(m_multi_var_init in current_settings.modeswitches) then
             Message(parser_e_initialized_only_one_var);
           if vo_is_thread_var in vs.varoptions then
             Message(parser_e_initialized_not_for_threadvar);
@@ -1156,7 +1160,11 @@ implementation
                   generation for LLVM) }
                 if not parse_generic then
                   begin
-                    vs.defaultconstsym:=tcsym;
+                    for i:=0 to sc.count-1 do
+                      begin
+                        tabstractnormalvarsym(sc[i]).defaultconstsym:=tcsym;
+                        tabstractnormalvarsym(sc[i]).varstate:=vs_initialised;
+                      end;
                     current_asmdata.asmlists[al_typedconsts].concatlist(templist);
                   end;
                 templist.free;
@@ -1165,12 +1173,33 @@ implementation
             staticvarsym :
               begin
                 maybe_guarantee_record_typesym(vs.vardef,vs.vardef.owner);
-                read_typed_const(current_asmdata.asmlists[al_typedconsts],tstaticvarsym(vs),false);
+                if sc.count<=1 then
+                  read_typed_const(current_asmdata.asmlists[al_typedconsts],tstaticvarsym(vs),false)
+                else
+                  begin
+                    { record tokens so we can replay them for each variable }
+                    already_recording:=current_scanner.is_recording_tokens;
+                    tokenbuf:=tdynamicarray.create(256);
+                    if not already_recording then
+                      current_scanner.startrecordtokens(tokenbuf);
+                    read_typed_const(current_asmdata.asmlists[al_typedconsts],tstaticvarsym(vs),false);
+                    if not already_recording then
+                      current_scanner.stoprecordtokens;
+                    for i:=1 to sc.count-1 do
+                      begin
+                        maybe_guarantee_record_typesym(tabstractnormalvarsym(sc[i]).vardef,tabstractnormalvarsym(sc[i]).vardef.owner);
+                        tokenbuf.seek(0);
+                        current_scanner.startreplaytokens(tokenbuf,false);
+                        read_typed_const(current_asmdata.asmlists[al_typedconsts],tstaticvarsym(sc[i]),false);
+                      end;
+                    tokenbuf.free;
+                  end;
               end;
             else
               internalerror(200611051);
           end;
-          vs.varstate:=vs_initialised;
+          for i:=0 to sc.count-1 do
+            tabstractnormalvarsym(sc[i]).varstate:=vs_initialised;
         end;
 
 {$ifdef gpc_mode}

compiler/pstatmnt.pas

@@ -1813,6 +1813,8 @@                       ((p.resultdef.typ=recorddef) or
         i              : longint;
         sc             : TFPObjectList;
         old_block_type : tblock_type;
+        statements     : tstatementnode;
+        tempnode        : ttempcreatenode;
       begin
         result := nil;
         consume(_VAR);
@@ -1867,14 +1869,36 @@                       ((p.resultdef.typ=recorddef) or
               if try_to_consume(_ASSIGNMENT) then
                 begin
                   { Only one variable may be initialised at a time. }
-                  if sc.count > 1 then
+                  if (sc.count > 1) and
+                     not(m_multi_var_init in current_settings.modeswitches) then
                     Message(parser_e_initialized_only_one_var);
                   block_type := old_block_type;
                   initexpr := expr(true);
-                  tabstractnormalvarsym(sc[0]).varstate := vs_initialised;
-                  result := cassignmentnode.create(
-                    cloadnode.create(tsym(sc[0]), tsym(sc[0]).owner),
-                    initexpr);
+                  if sc.count = 1 then
+                    begin
+                      tabstractnormalvarsym(sc[0]).varstate := vs_initialised;
+                      result := cassignmentnode.create(
+                        cloadnode.create(tsym(sc[0]), tsym(sc[0]).owner),
+                        initexpr);
+                    end
+                  else
+                    begin
+                      { multi-var: temp := expr; a := temp; b := temp; }
+                      do_typecheckpass(initexpr);
+                      result := internalstatements(statements);
+                      tempnode := ctempcreatenode.create(hdef, hdef.size, tt_persistent, true);
+                      addstatement(statements, tempnode);
+                      addstatement(statements, cassignmentnode.create(
+                        ctemprefnode.create(tempnode), initexpr));
+                      for i := 0 to sc.count - 1 do
+                        begin
+                          tabstractnormalvarsym(sc[i]).varstate := vs_initialised;
+                          addstatement(statements, cassignmentnode.create(
+                            cloadnode.create(tsym(sc[i]), tsym(sc[i]).owner),
+                            ctemprefnode.create(tempnode)));
+                        end;
+                      addstatement(statements, ctempdeletenode.create(tempnode));
+                    end;
                 end
               else
                 result := cnothingnode.create;

compiler/utils/ppuutils/ppudump.pp

@@ -2497,7 +2497,8 @@ (*     tsettings = record
          'm_statement_expressions', { enables expressions using statements like if, case, try }
          'm_array_equality',      { enables equality operator in addition to ArrayOperators modeswitch }
          'm_no_rtti',             { hides RTTI ASCII text }
-         'm_inline_var'           { allow inline variable declarations inside statement blocks }
+         'm_inline_var',          { allow inline variable declarations inside statement blocks }
+         'm_multi_var_init'       { allow initializing multiple variables in one declaration }
        );
        { optimizer }
        optimizerswitchname : array[toptimizerswitch] of string[50] =