Check for non-void functions that execute to the end without returning a value.

This generalizes the heuristic approach for checking whether _Noreturn functions could execute to the end of the function, extending it to apply to any function with a non-void return type. These checks use the same #pragma lint bit but give different messages depending on the situation.

CCommon.pas

@@ -92,7 +92,7 @@ const
    lintPrintf           = $0010;        {check printf/scanf format flags}
    lintOverflow         = $0020;        {check for overflows}
    lintC99Syntax        = $0040;        {check for syntax that C99 disallows}
-   lintNoreturn         = $0080;        {check for return in _Noreturn funcs}
+   lintReturn           = $0080;        {flag issues with how functions return}
 
                                         {bit masks for GetLInfo flags}
                                         {----------------------------}
@@ -505,6 +505,7 @@ var
    wait: boolean;                       {wait for keypress after errors?}
    lintIsError: boolean;                {treat lint messages as errors?}
    fIsNoreturn: boolean;                {is the current function _Noreturn?}
+   doingMain: boolean;                  {are we processing the main function?}
 
                                         {syntactic classes of tokens}
                                         {---------------------------}

DAG.pas

@@ -4823,9 +4823,10 @@ var
    end; {Generate}
    
    
-   procedure CheckNoreturn;
+   procedure CheckReturn;
    
-   { Check if a noreturn function looks like it might return.   }
+   { Check if a noreturn function looks like it might return,   }
+   { or if a non-void function might return with no value.      }
    {                                                            }
    { This uses a heuristic of basically looking for code at the }
    { end of the function that would lead to it returning if     }
@@ -4838,17 +4839,22 @@ var
    var
       code: icptr;
 
-   begin {CheckNoreturn}
+   begin {CheckReturn}
    code := DAGhead;
-   while code^.opcode in [pc_nop,pc_ret,pc_lnm,dc_lab,dc_loc,pc_add] do
+   while code^.opcode in [pc_lnm,dc_lab,dc_loc,pc_add] do
       code := code^.next;
    while code^.opcode = pc_pop do
       code := code^.left;
    while code^.opcode = pc_bno do
       code := code^.right;
    if not (code^.opcode in [pc_fjp,pc_tjp,pc_ujp,pc_xjp,pc_cui,pc_cup,pc_tl1])
-      then Error(154);
-   end; {CheckNoreturn}
+      then begin
+      if fIsNoreturn then
+         Error(154)
+      else
+         Error(155);
+      end;
+   end; {CheckReturn}
 
 
    procedure Push (code: icptr);
@@ -4938,9 +4944,17 @@ case code^.opcode of
    pc_gil, pc_gli, pc_gdl, pc_gld, pc_lil, pc_lli, pc_ldl, pc_lld,
    pc_lad, pc_lao, pc_lca, pc_lda, pc_ldc, pc_ldo, pc_lod, pc_nop,
    dc_cns, dc_glb, dc_dst, pc_lnm, pc_nam, pc_nat, dc_lab, pc_add,
-   pc_ujp, dc_pin, pc_ent, pc_ret, dc_sym:
+   pc_ujp, dc_pin, pc_ent, dc_sym:
       Push(code);
 
+   pc_ret:
+      begin
+      if (lint & lintReturn) <> 0 then
+         if fIsNoreturn or ((code^.optype <> cgVoid) and not doingMain) then
+            CheckReturn;
+      Push(code);
+      end;
+
    pc_cnn:
       begin
       code^.opcode := pc_cnv;
@@ -4968,9 +4982,6 @@ case code^.opcode of
       end;
 
    dc_enp: begin
-      if fIsNoreturn then
-         if (lint & lintNoreturn) <> 0 then
-            CheckNoreturn;
       Push(code);
       Reverse;
       Generate;

Parser.pas

@@ -151,7 +151,6 @@ type
       end;
 
 var
-   doingMain: boolean;                  {are we processing the main function?}
    firstCompoundStatement: boolean;     {are we doing a function level compound statement?}
    fType: typePtr;                      {return type of the current function}
    isForwardDeclared: boolean;          {is the field list component           }
@@ -739,7 +738,7 @@ var
 
    begin {ReturnStatement}
    if fIsNoreturn then
-      if (lint & lintNoreturn) <> 0 then
+      if (lint & lintReturn) <> 0 then
          Error(153);
    NextToken;                           {skip the 'return' token}
    if token.kind <> semicolonch then    {if present, evaluate the return value}
@@ -770,7 +769,7 @@ var
       end {if}
    else begin
       if (fType^.kind <> scalarType) or (fType^.baseType <> cgVoid) then
-         if (lint & lintC99Syntax) <> 0 then
+         if ((lint & lintC99Syntax) <> 0) or ((lint & lintReturn) <> 0) then
             Error(152);
       end; {else}
    Gen1(pc_ujp, returnLabel);           {branch to the exit point}

Scanner.pas

@@ -183,7 +183,7 @@ const
                                         {----}
    defaultName  = '13:ORCACDefs:Defaults.h'; {default include file name}
    maxErr       = 10;                   {max errors on one line}
-   maxLint      = 154;                  {maximum lint error code}
+   maxLint      = 155;                  {maximum lint error code}
 
 type
    errorType = record                   {record of a single error}
@@ -682,6 +682,7 @@ if list or (numErr <> 0) then begin
         152: msg := @'lint: return with no value in non-void function';
         153: msg := @'lint: return statement in function declared _Noreturn';
         154: msg := @'lint: function declared _Noreturn can return or has unreachable code';
+        155: msg := @'lint: non-void function may not return a value or has unreachable code';
          otherwise: Error(57);
          end; {case}
        writeln(msg^);
@@ -3683,7 +3684,7 @@ lintIsError := true;                    {lint messages are considered errors}
 
                                         {error codes for lint messages}
                                         {if changed, also change maxLint}
-lintErrors := [51,104,105,110,124,125,128,129,130,147,151,152,153,154];
+lintErrors := [51,104,105,110,124,125,128,129,130,147,151,152,153,154,155];
 
 spaceStr := ' ';                        {strings used in stringization}
 quoteStr := '"';