cc65/src/cc65/stmt.c

/*****************************************************************************/
/*                                                                           */
/*                                  stmt.c                                   */
/*                                                                           */
/*                             Parse a statement                             */
/*                                                                           */
/*                                                                           */
/*                                                                           */
/* (C) 1998-2010, Ullrich von Bassewitz                                      */
/*                Roemerstrasse 52                                           */
/*                D-70794 Filderstadt                                        */
/* EMail:         uz@cc65.org                                                */
/*                                                                           */
/*                                                                           */
/* This software is provided 'as-is', without any expressed or implied       */
/* warranty.  In no event will the authors be held liable for any damages    */
/* arising from the use of this software.                                    */
/*                                                                           */
/* Permission is granted to anyone to use this software for any purpose,     */
/* including commercial applications, and to alter it and redistribute it    */
/* freely, subject to the following restrictions:                            */
/*                                                                           */
/* 1. The origin of this software must not be misrepresented; you must not   */
/*    claim that you wrote the original software. If you use this software   */
/*    in a product, an acknowledgment in the product documentation would be  */
/*    appreciated but is not required.                                       */
/* 2. Altered source versions must be plainly marked as such, and must not   */
/*    be misrepresented as being the original software.                      */
/* 3. This notice may not be removed or altered from any source              */
/*    distribution.                                                          */
/*                                                                           */
/*****************************************************************************/



#include <stdio.h>
#include <string.h>

/* common */
#include "coll.h"
#include "xmalloc.h"

/* cc65 */
#include "asmcode.h"
#include "asmlabel.h"
#include "codegen.h"
#include "datatype.h"
#include "error.h"
#include "expr.h"
#include "function.h"
#include "global.h"
#include "goto.h"
#include "litpool.h"
#include "loadexpr.h"
#include "locals.h"
#include "loop.h"
#include "pragma.h"
#include "scanner.h"
#include "stackptr.h"
#include "stmt.h"
#include "swstmt.h"
#include "symtab.h"
#include "testexpr.h"
#include "typeconv.h"



/*****************************************************************************/
/*                             Helper functions                              */
/*****************************************************************************/



static int CheckLabelWithoutStatement (void)
/* Called from Statement() after a label definition. Will check for a
** following closing curly brace. This means that a label is not followed
** by a statement which is required by the standard. Output an error if so.
*/
{
    if (CurTok.Tok == TOK_RCURLY) {
        Error ("Label at end of compound statement");
        return 1;
    } else {
        return 0;
    }
}



static void CheckTok (token_t Tok, const char* Msg, int* PendingToken)
/* Helper function for Statement. Will check for Tok and print Msg if not
** found. If PendingToken is NULL, it will the skip the token, otherwise
** it will store one to PendingToken.
*/
{
    if (CurTok.Tok != Tok) {
        Error ("%s", Msg);
    } else if (PendingToken) {
        *PendingToken = 1;
    } else {
        NextToken ();
    }
}



static void CheckSemi (int* PendingToken)
/* Helper function for Statement. Will check for a semicolon and print an
** error message if not found (plus some error recovery). If PendingToken is
** NULL, it will the skip the token, otherwise it will store one to
** PendingToken.
** This function is a special version of CheckTok with the addition of the
** error recovery.
*/
{
    int HaveToken = (CurTok.Tok == TOK_SEMI);
    if (!HaveToken) {
        Error ("';' expected");
        /* Try to be smart about errors */
        if (CurTok.Tok == TOK_COLON || CurTok.Tok == TOK_COMMA) {
            HaveToken = 1;
        }
    }
    if (HaveToken) {
        if (PendingToken) {
            *PendingToken = 1;
        } else {
            NextToken ();
        }
    }
}



static void SkipPending (int PendingToken)
/* Skip the pending token if we have one */
{
    if (PendingToken) {
        NextToken ();
    }
}



/*****************************************************************************/
/*                                   Code                                    */
/*****************************************************************************/



static int IfStatement (void)
/* Handle an 'if' statement */
{
    unsigned Label1;
    unsigned TestResult;
    int GotBreak;

    /* Skip the if */
    NextToken ();

    /* Generate a jump label and parse the condition */
    Label1 = GetLocalLabel ();
    TestResult = TestInParens (Label1, 0);

    /* Parse the if body */
    GotBreak = Statement (0);

    /* Else clause present? */
    if (CurTok.Tok != TOK_ELSE) {

        g_defcodelabel (Label1);

        /* Since there's no else clause, we're not sure, if the a break
        ** statement is really executed.
        */
        return 0;

    } else {

        /* Generate a jump around the else branch */
        unsigned Label2 = GetLocalLabel ();
        g_jump (Label2);

        /* Skip the else */
        NextToken ();

        /* If the if expression was always true, the code in the else branch
        ** is never executed. Output a warning if this is the case.
        */
        if (TestResult == TESTEXPR_TRUE) {
            Warning ("Unreachable code");
        }

        /* Define the target for the first test */
        g_defcodelabel (Label1);

        /* Total break only if both branches had a break. */
        GotBreak &= Statement (0);

        /* Generate the label for the else clause */
        g_defcodelabel (Label2);

        /* Done */
        return GotBreak;
    }
}



static void DoStatement (void)
/* Handle the 'do' statement */
{
    /* Get the loop control labels */
    unsigned LoopLabel      = GetLocalLabel ();
    unsigned BreakLabel     = GetLocalLabel ();
    unsigned ContinueLabel  = GetLocalLabel ();

    /* Skip the while token */
    NextToken ();

    /* Add the loop to the loop stack */
    AddLoop (BreakLabel, ContinueLabel);

    /* Define the loop label */
    g_defcodelabel (LoopLabel);

    /* Parse the loop body */
    Statement (0);

    /* Output the label for a continue */
    g_defcodelabel (ContinueLabel);

    /* Parse the end condition */
    Consume (TOK_WHILE, "'while' expected");
    TestInParens (LoopLabel, 1);
    ConsumeSemi ();

    /* Define the break label */
    g_defcodelabel (BreakLabel);

    /* Remove the loop from the loop stack */
    DelLoop ();
}



static void WhileStatement (void)
/* Handle the 'while' statement */
{
    int         PendingToken;
    CodeMark    CondCodeStart;  /* Start of condition evaluation code */
    CodeMark    CondCodeEnd;    /* End of condition evaluation code */
    CodeMark    Here;           /* "Here" location of code */

    /* Get the loop control labels */
    unsigned LoopLabel  = GetLocalLabel ();
    unsigned BreakLabel = GetLocalLabel ();
    unsigned CondLabel  = GetLocalLabel ();

    /* Skip the while token */
    NextToken ();

    /* Add the loop to the loop stack. In case of a while loop, the condition
    ** label is used for continue statements.
    */
    AddLoop (BreakLabel, CondLabel);

    /* We will move the code that evaluates the while condition to the end of
    ** the loop, so generate a jump here.
    */
    g_jump (CondLabel);

    /* Remember the current position */
    GetCodePos (&CondCodeStart);

    /* Test the loop condition */
    TestInParens (LoopLabel, 1);

    /* Remember the end of the condition evaluation code */
    GetCodePos (&CondCodeEnd);

    /* Define the head label */
    g_defcodelabel (LoopLabel);

    /* Loop body */
    Statement (&PendingToken);

    /* Emit the while condition label */
    g_defcodelabel (CondLabel);

    /* Move the test code here */
    GetCodePos (&Here);
    MoveCode (&CondCodeStart, &CondCodeEnd, &Here);

    /* Exit label */
    g_defcodelabel (BreakLabel);

    /* Eat remaining tokens that were delayed because of line info
    ** correctness
    */
    SkipPending (PendingToken);

    /* Remove the loop from the loop stack */
    DelLoop ();
}



static void ReturnStatement (void)
/* Handle the 'return' statement */
{
    ExprDesc Expr;

    NextToken ();
    if (CurTok.Tok != TOK_SEMI) {

        /* Evaluate the return expression */
        hie0 (&Expr);

        /* If we return something in a void function, print an error and
        ** ignore the value. Otherwise convert the value to the type of the
        ** return.
        */
        if (F_HasVoidReturn (CurrentFunc)) {
            Error ("Returning a value in function with return type void");
        } else {
            /* Convert the return value to the type of the function result */
            TypeConversion (&Expr, F_GetReturnType (CurrentFunc));

            /* Load the value into the primary */
            LoadExpr (CF_NONE, &Expr);
        }

    } else if (!F_HasVoidReturn (CurrentFunc) && !F_HasOldStyleIntRet (CurrentFunc)) {
        Error ("Function '%s' must return a value", F_GetFuncName (CurrentFunc));
    }

    /* Mark the function as having a return statement */
    F_ReturnFound (CurrentFunc);

    /* Cleanup the stack in case we're inside a block with locals */
    g_space (StackPtr - F_GetTopLevelSP (CurrentFunc));

    /* Output a jump to the function exit code */
    g_jump (F_GetRetLab (CurrentFunc));
}



static void BreakStatement (void)
/* Handle the 'break' statement */
{
    LoopDesc* L;

    /* Skip the break */
    NextToken ();

    /* Get the current loop descriptor */
    L = CurrentLoop ();

    /* Check if we are inside a loop */
    if (L == 0) {
        /* Error: No current loop */
        Error ("'break' statement not within loop or switch");
        return;
    }

    /* Correct the stack pointer if needed */
    g_space (StackPtr - L->StackPtr);

    /* Jump to the exit label of the loop */
    g_jump (L->BreakLabel);
}



static void ContinueStatement (void)
/* Handle the 'continue' statement */
{
    LoopDesc* L;

    /* Skip the continue */
    NextToken ();

    /* Get the current loop descriptor */
    L = CurrentLoop ();
    if (L) {
        /* Search for a loop that has a continue label. */
        do {
            if (L->ContinueLabel) {
                break;
            }
            L = L->Next;
        } while (L);
    }

    /* Did we find it? */
    if (L == 0) {
        Error ("'continue' statement not within a loop");
        return;
    }

    /* Correct the stackpointer if needed */
    g_space (StackPtr - L->StackPtr);

    /* Jump to next loop iteration */
    g_jump (L->ContinueLabel);
}



static void ForStatement (void)
/* Handle a 'for' statement */
{
    ExprDesc lval1;
    ExprDesc lval3;
    int HaveIncExpr;
    CodeMark IncExprStart;
    CodeMark IncExprEnd;
    int PendingToken;

    /* Get several local labels needed later */
    unsigned TestLabel    = GetLocalLabel ();
    unsigned BreakLabel   = GetLocalLabel ();
    unsigned IncLabel     = GetLocalLabel ();
    unsigned BodyLabel    = GetLocalLabel ();

    /* Skip the FOR token */
    NextToken ();

    /* Add the loop to the loop stack. A continue jumps to the start of the
    ** the increment condition.
    */
    AddLoop (BreakLabel, IncLabel);

    /* Skip the opening paren */
    ConsumeLParen ();

    /* Parse the initializer expression */
    if (CurTok.Tok != TOK_SEMI) {
        Expression0 (&lval1);
    }
    ConsumeSemi ();

    /* Label for the test expressions */
    g_defcodelabel (TestLabel);

    /* Parse the test expression */
    if (CurTok.Tok != TOK_SEMI) {
        Test (BodyLabel, 1);
        g_jump (BreakLabel);
    } else {
        g_jump (BodyLabel);
    }
    ConsumeSemi ();

    /* Remember the start of the increment expression */
    GetCodePos (&IncExprStart);

    /* Label for the increment expression */
    g_defcodelabel (IncLabel);

    /* Parse the increment expression */
    HaveIncExpr = (CurTok.Tok != TOK_RPAREN);
    if (HaveIncExpr) {
        Expression0 (&lval3);
    }

    /* Jump to the test */
    g_jump (TestLabel);

    /* Remember the end of the increment expression */
    GetCodePos (&IncExprEnd);

    /* Skip the closing paren */
    ConsumeRParen ();

    /* Loop body */
    g_defcodelabel (BodyLabel);
    Statement (&PendingToken);

    /* If we had an increment expression, move the code to the bottom of
    ** the loop. In this case we don't need to jump there at the end of
    ** the loop body.
    */
    if (HaveIncExpr) {
        CodeMark Here;
        GetCodePos (&Here);
        MoveCode (&IncExprStart, &IncExprEnd, &Here);
    } else {
        /* Jump back to the increment expression */
        g_jump (IncLabel);
    }

    /* Skip a pending token if we have one */
    SkipPending (PendingToken);

    /* Declare the break label */
    g_defcodelabel (BreakLabel);

    /* Remove the loop from the loop stack */
    DelLoop ();
}



static int CompoundStatement (void)
/* Compound statement. Allow any number of statements inside braces. The
** function returns true if the last statement was a break or return.
*/
{
    int GotBreak;

    /* Remember the stack at block entry */
    int OldStack = StackPtr;
    unsigned OldBlockStackSize = CollCount (&CurrentFunc->LocalsBlockStack);

    /* Enter a new lexical level */
    EnterBlockLevel ();

    /* Parse local variable declarations if any */
    DeclareLocals ();

    /* Now process statements in this block */
    GotBreak = 0;
    while (CurTok.Tok != TOK_RCURLY) {
        if (CurTok.Tok != TOK_CEOF) {
            GotBreak = Statement (0);
        } else {
            break;
        }
    }

    /* Clean up the stack. */
    if (!GotBreak) {
        g_space (StackPtr - OldStack);
    }

    /* If the segment had autoinited variables, let's pop it of a stack
    ** of such blocks.
    */
    if (OldBlockStackSize != CollCount (&CurrentFunc->LocalsBlockStack)) {
        CollPop (&CurrentFunc->LocalsBlockStack);
    }

    StackPtr = OldStack;

    /* Emit references to imports/exports for this block */
    EmitExternals ();

    /* Leave the lexical level */
    LeaveBlockLevel ();

    return GotBreak;
}



int Statement (int* PendingToken)
/* Statement parser. Returns 1 if the statement does a return/break, returns
** 0 otherwise. If the PendingToken pointer is not NULL, the function will
** not skip the terminating token of the statement (closing brace or
** semicolon), but store true if there is a pending token, and false if there
** is none. The token is always checked, so there is no need for the caller to
** check this token, it must be skipped, however. If the argument pointer is
** NULL, the function will skip the token.
*/
{
    ExprDesc Expr;
    int GotBreak;
    CodeMark Start, End;

    /* Assume no pending token */
    if (PendingToken) {
        *PendingToken = 0;
    }

    /* Check for a label. A label is always part of a statement, it does not
    ** replace one.
    */
    while (CurTok.Tok == TOK_IDENT && NextTok.Tok == TOK_COLON) {
        /* Handle the label */
        DoLabel ();
        if (CheckLabelWithoutStatement ()) {
            return 0;
        }
    }

    switch (CurTok.Tok) {

        case TOK_LCURLY:
            NextToken ();
            GotBreak = CompoundStatement ();
            CheckTok (TOK_RCURLY, "'{' expected", PendingToken);
            return GotBreak;

        case TOK_IF:
            return IfStatement ();

        case TOK_WHILE:
            WhileStatement ();
            break;

        case TOK_DO:
            DoStatement ();
            break;

        case TOK_SWITCH:
            SwitchStatement ();
            break;

        case TOK_RETURN:
            ReturnStatement ();
            CheckSemi (PendingToken);
            return 1;

        case TOK_BREAK:
            BreakStatement ();
            CheckSemi (PendingToken);
            return 1;

        case TOK_CONTINUE:
            ContinueStatement ();
            CheckSemi (PendingToken);
            return 1;

        case TOK_FOR:
            ForStatement ();
            break;

        case TOK_GOTO:
            GotoStatement ();
            CheckSemi (PendingToken);
            return 1;

        case TOK_SEMI:
            /* Ignore it */
            CheckSemi (PendingToken);
            break;

        case TOK_PRAGMA:
            DoPragma ();
            break;

        case TOK_CASE:
            CaseLabel ();
            CheckLabelWithoutStatement ();
            break;

        case TOK_DEFAULT:
            DefaultLabel ();
            CheckLabelWithoutStatement ();
            break;

        default:
            /* Remember the current code position */
            GetCodePos (&Start);
            /* Actual statement */
            ExprWithCheck (hie0, &Expr);
            /* Load the result only if it is an lvalue and the type is
            ** marked as volatile. Otherwise the load is useless.
            */
            if (ED_IsLVal (&Expr) && IsQualVolatile (Expr.Type)) {
                LoadExpr (CF_NONE, &Expr);
            }
            /* If the statement didn't generate code, and is not of type
            ** void, emit a warning.
            */
            GetCodePos (&End);
            if (CodeRangeIsEmpty (&Start, &End) &&
                !IsTypeVoid (Expr.Type)         &&
                IS_Get (&WarnNoEffect)) {
                Warning ("Statement has no effect");
            }
            CheckSemi (PendingToken);
    }
    return 0;
}