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tclCompExpr.c

/* 
 * tclCompExpr.c --
 *
 *    This file contains the code to compile Tcl expressions.
 *
 * Copyright (c) 1997 Sun Microsystems, Inc.
 * Copyright (c) 1998-2000 by Scriptics Corporation.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclCompExpr.c,v 1.13.2.2 2005/11/27 02:34:41 das Exp $
 */

#include "tclInt.h"
#include "tclCompile.h"

/*
 * The stuff below is a bit of a hack so that this file can be used in
 * environments that include no UNIX, i.e. no errno: just arrange to use
 * the errno from tclExecute.c here.
 */

#ifndef TCL_GENERIC_ONLY
#include "tclPort.h"
#else
#define NO_ERRNO_H
#endif

#ifdef NO_ERRNO_H
extern int errno;             /* Use errno from tclExecute.c. */
#define ERANGE 34
#endif

/*
 * Boolean variable that controls whether expression compilation tracing
 * is enabled.
 */

#ifdef TCL_COMPILE_DEBUG
static int traceExprComp = 0;
#endif /* TCL_COMPILE_DEBUG */

/*
 * The ExprInfo structure describes the state of compiling an expression.
 * A pointer to an ExprInfo record is passed among the routines in
 * this module.
 */

typedef struct ExprInfo {
    Tcl_Interp *interp;       /* Used for error reporting. */
    Tcl_Parse *parsePtr;      /* Structure filled with information about
                         * the parsed expression. */
    CONST char *expr;         /* The expression that was originally passed
                         * to TclCompileExpr. */
    CONST char *lastChar;     /* Points just after last byte of expr. */
    int hasOperators;         /* Set 1 if the expr has operators; 0 if
                         * expr is only a primary. If 1 after
                         * compiling an expr, a tryCvtToNumeric
                         * instruction is emitted to convert the
                         * primary to a number if possible. */
} ExprInfo;

/*
 * Definitions of numeric codes representing each expression operator.
 * The order of these must match the entries in the operatorTable below.
 * Also the codes for the relational operators (OP_LESS, OP_GREATER, 
 * OP_LE, OP_GE, OP_EQ, and OP_NE) must be consecutive and in that order.
 * Note that OP_PLUS and OP_MINUS represent both unary and binary operators.
 */

#define OP_MULT         0
#define OP_DIVIDE 1
#define OP_MOD          2
#define OP_PLUS         3
#define OP_MINUS  4
#define OP_LSHIFT 5
#define OP_RSHIFT 6
#define OP_LESS         7
#define OP_GREATER      8
#define OP_LE           9
#define OP_GE           10
#define OP_EQ           11
#define OP_NEQ          12
#define OP_BITAND 13
#define OP_BITXOR 14
#define OP_BITOR  15
#define OP_LAND         16
#define OP_LOR          17
#define OP_QUESTY 18
#define OP_LNOT         19
#define OP_BITNOT 20
#define OP_STREQ  21
#define OP_STRNEQ 22

/*
 * Table describing the expression operators. Entries in this table must
 * correspond to the definitions of numeric codes for operators just above.
 */

static int opTableInitialized = 0; /* 0 means not yet initialized. */

TCL_DECLARE_MUTEX(opMutex)

typedef struct OperatorDesc {
    char *name;               /* Name of the operator. */
    int numOperands;          /* Number of operands. 0 if the operator
                         * requires special handling. */
    int instruction;          /* Instruction opcode for the operator.
                         * Ignored if numOperands is 0. */
} OperatorDesc;

static OperatorDesc operatorTable[] = {
    {"*",   2,  INST_MULT},
    {"/",   2,  INST_DIV},
    {"%",   2,  INST_MOD},
    {"+",   0}, 
    {"-",   0},
    {"<<",  2,  INST_LSHIFT},
    {">>",  2,  INST_RSHIFT},
    {"<",   2,  INST_LT},
    {">",   2,  INST_GT},
    {"<=",  2,  INST_LE},
    {">=",  2,  INST_GE},
    {"==",  2,  INST_EQ},
    {"!=",  2,  INST_NEQ},
    {"&",   2,  INST_BITAND},
    {"^",   2,  INST_BITXOR},
    {"|",   2,  INST_BITOR},
    {"&&",  0},
    {"||",  0},
    {"?",   0},
    {"!",   1,  INST_LNOT},
    {"~",   1,  INST_BITNOT},
    {"eq",  2,  INST_STR_EQ},
    {"ne",  2,  INST_STR_NEQ},
    {NULL}
};

/*
 * Hashtable used to map the names of expression operators to the index
 * of their OperatorDesc description.
 */

static Tcl_HashTable opHashTable;

/*
 * Declarations for local procedures to this file:
 */

static int        CompileCondExpr _ANSI_ARGS_((
                      Tcl_Token *exprTokenPtr, ExprInfo *infoPtr,
                      CompileEnv *envPtr, Tcl_Token **endPtrPtr));
static int        CompileLandOrLorExpr _ANSI_ARGS_((
                      Tcl_Token *exprTokenPtr, int opIndex,
                      ExprInfo *infoPtr, CompileEnv *envPtr,
                      Tcl_Token **endPtrPtr));
static int        CompileMathFuncCall _ANSI_ARGS_((
                      Tcl_Token *exprTokenPtr, CONST char *funcName,
                      ExprInfo *infoPtr, CompileEnv *envPtr,
                      Tcl_Token **endPtrPtr));
static int        CompileSubExpr _ANSI_ARGS_((
                      Tcl_Token *exprTokenPtr, ExprInfo *infoPtr,
                      CompileEnv *envPtr));
static void       LogSyntaxError _ANSI_ARGS_((ExprInfo *infoPtr));

/*
 * Macro used to debug the execution of the expression compiler.
 */

#ifdef TCL_COMPILE_DEBUG
#define TRACE(exprBytes, exprLength, tokenBytes, tokenLength) \
    if (traceExprComp) { \
      fprintf(stderr, "CompileSubExpr: \"%.*s\", token \"%.*s\"\n", \
              (exprLength), (exprBytes), (tokenLength), (tokenBytes)); \
    }
#else
#define TRACE(exprBytes, exprLength, tokenBytes, tokenLength)
#endif /* TCL_COMPILE_DEBUG */

/*
 *----------------------------------------------------------------------
 *
 * TclCompileExpr --
 *
 *    This procedure compiles a string containing a Tcl expression into
 *    Tcl bytecodes. This procedure is the top-level interface to the
 *    the expression compilation module, and is used by such public
 *    procedures as Tcl_ExprString, Tcl_ExprStringObj, Tcl_ExprLong,
 *    Tcl_ExprDouble, Tcl_ExprBoolean, and Tcl_ExprBooleanObj.
 *
 * Results:
 *    The return value is TCL_OK on a successful compilation and TCL_ERROR
 *    on failure. If TCL_ERROR is returned, then the interpreter's result
 *    contains an error message.
 *
 * Side effects:
 *    Adds instructions to envPtr to evaluate the expression at runtime.
 *
 *----------------------------------------------------------------------
 */

int
TclCompileExpr(interp, script, numBytes, envPtr)
    Tcl_Interp *interp;       /* Used for error reporting. */
    CONST char *script;       /* The source script to compile. */
    int numBytes;       /* Number of bytes in script. If < 0, the
                         * string consists of all bytes up to the
                         * first null character. */
    CompileEnv *envPtr;       /* Holds resulting instructions. */
{
    ExprInfo info;
    Tcl_Parse parse;
    Tcl_HashEntry *hPtr;
    int new, i, code;

    /*
     * If this is the first time we've been called, initialize the table
     * of expression operators.
     */

    if (numBytes < 0) {
      numBytes = (script? strlen(script) : 0);
    }
    if (!opTableInitialized) {
      Tcl_MutexLock(&opMutex);
      if (!opTableInitialized) {
          Tcl_InitHashTable(&opHashTable, TCL_STRING_KEYS);
          for (i = 0;  operatorTable[i].name != NULL;  i++) {
            hPtr = Tcl_CreateHashEntry(&opHashTable,
                  operatorTable[i].name, &new);
            if (new) {
                Tcl_SetHashValue(hPtr, (ClientData) i);
            }
          }
          opTableInitialized = 1;
      }
      Tcl_MutexUnlock(&opMutex);
    }

    /*
     * Initialize the structure containing information abvout this
     * expression compilation.
     */

    info.interp = interp;
    info.parsePtr = &parse;
    info.expr = script;
    info.lastChar = (script + numBytes); 
    info.hasOperators = 0;

    /*
     * Parse the expression then compile it.
     */

    code = Tcl_ParseExpr(interp, script, numBytes, &parse);
    if (code != TCL_OK) {
      goto done;
    }

    code = CompileSubExpr(parse.tokenPtr, &info, envPtr);
    if (code != TCL_OK) {
      Tcl_FreeParse(&parse);
      goto done;
    }
    
    if (!info.hasOperators) {
      /*
       * Attempt to convert the primary's object to an int or double.
       * This is done in order to support Tcl's policy of interpreting
       * operands if at all possible as first integers, else
       * floating-point numbers.
       */
      
      TclEmitOpcode(INST_TRY_CVT_TO_NUMERIC, envPtr);
    }
    Tcl_FreeParse(&parse);

    done:
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * TclFinalizeCompilation --
 *
 *    Clean up the compilation environment so it can later be
 *    properly reinitialized. This procedure is called by Tcl_Finalize().
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Cleans up the compilation environment. At the moment, just the
 *    table of expression operators is freed.
 *
 *----------------------------------------------------------------------
 */

void
TclFinalizeCompilation()
{
    Tcl_MutexLock(&opMutex);
    if (opTableInitialized) {
        Tcl_DeleteHashTable(&opHashTable);
        opTableInitialized = 0;
    }
    Tcl_MutexUnlock(&opMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * CompileSubExpr --
 *
 *    Given a pointer to a TCL_TOKEN_SUB_EXPR token describing a
 *    subexpression, this procedure emits instructions to evaluate the
 *    subexpression at runtime.
 *
 * Results:
 *    The return value is TCL_OK on a successful compilation and TCL_ERROR
 *    on failure. If TCL_ERROR is returned, then the interpreter's result
 *    contains an error message.
 *
 * Side effects:
 *    Adds instructions to envPtr to evaluate the subexpression.
 *
 *----------------------------------------------------------------------
 */

static int
CompileSubExpr(exprTokenPtr, infoPtr, envPtr)
    Tcl_Token *exprTokenPtr;  /* Points to TCL_TOKEN_SUB_EXPR token
                         * to compile. */
    ExprInfo *infoPtr;        /* Describes the compilation state for the
                         * expression being compiled. */
    CompileEnv *envPtr;       /* Holds resulting instructions. */
{
    Tcl_Interp *interp = infoPtr->interp;
    Tcl_Token *tokenPtr, *endPtr = NULL; /* silence gcc 4 warning */
    Tcl_Token *afterSubexprPtr;
    OperatorDesc *opDescPtr;
    Tcl_HashEntry *hPtr;
    CONST char *operator;
    Tcl_DString opBuf;
    int objIndex, opIndex, length, code;
    char buffer[TCL_UTF_MAX];

    if (exprTokenPtr->type != TCL_TOKEN_SUB_EXPR) {
      panic("CompileSubExpr: token type %d not TCL_TOKEN_SUB_EXPR\n",
              exprTokenPtr->type);
    }
    code = TCL_OK;

    /*
     * Switch on the type of the first token after the subexpression token.
     * After processing it, advance tokenPtr to point just after the
     * subexpression's last token.
     */
    
    tokenPtr = exprTokenPtr+1;
    TRACE(exprTokenPtr->start, exprTokenPtr->size,
          tokenPtr->start, tokenPtr->size);
    switch (tokenPtr->type) {
        case TCL_TOKEN_WORD:
          code = TclCompileTokens(interp, tokenPtr+1,
                  tokenPtr->numComponents, envPtr);
          if (code != TCL_OK) {
            goto done;
          }
          tokenPtr += (tokenPtr->numComponents + 1);
          break;
          
        case TCL_TOKEN_TEXT:
          if (tokenPtr->size > 0) {
            objIndex = TclRegisterNewLiteral(envPtr, tokenPtr->start,
                      tokenPtr->size);
          } else {
            objIndex = TclRegisterNewLiteral(envPtr, "", 0);
          }
          TclEmitPush(objIndex, envPtr);
          tokenPtr += 1;
          break;
          
        case TCL_TOKEN_BS:
          length = Tcl_UtfBackslash(tokenPtr->start, (int *) NULL,
                buffer);
          if (length > 0) {
            objIndex = TclRegisterNewLiteral(envPtr, buffer, length);
          } else {
            objIndex = TclRegisterNewLiteral(envPtr, "", 0);
          }
          TclEmitPush(objIndex, envPtr);
          tokenPtr += 1;
          break;
          
        case TCL_TOKEN_COMMAND:
          code = TclCompileScript(interp, tokenPtr->start+1,
                tokenPtr->size-2, /*nested*/ 0, envPtr);
          if (code != TCL_OK) {
            goto done;
          }
          tokenPtr += 1;
          break;
          
        case TCL_TOKEN_VARIABLE:
          code = TclCompileTokens(interp, tokenPtr, 1, envPtr);
          if (code != TCL_OK) {
            goto done;
          }
          tokenPtr += (tokenPtr->numComponents + 1);
          break;
          
        case TCL_TOKEN_SUB_EXPR:
          code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
          if (code != TCL_OK) {
            goto done;
          }
          tokenPtr += (tokenPtr->numComponents + 1);
          break;
          
        case TCL_TOKEN_OPERATOR:
          /*
           * Look up the operator.  If the operator isn't found, treat it
           * as a math function.
           */
          Tcl_DStringInit(&opBuf);
          operator = Tcl_DStringAppend(&opBuf, 
                tokenPtr->start, tokenPtr->size);
          hPtr = Tcl_FindHashEntry(&opHashTable, operator);
          if (hPtr == NULL) {
            code = CompileMathFuncCall(exprTokenPtr, operator, infoPtr,
                  envPtr, &endPtr);
            Tcl_DStringFree(&opBuf);
            if (code != TCL_OK) {
                goto done;
            }
            tokenPtr = endPtr;
            break;
          }
          Tcl_DStringFree(&opBuf);
          opIndex = (int) Tcl_GetHashValue(hPtr);
          opDescPtr = &(operatorTable[opIndex]);

          /*
           * If the operator is "normal", compile it using information
           * from the operator table.
           */

          if (opDescPtr->numOperands > 0) {
            tokenPtr++;
            code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
            if (code != TCL_OK) {
                goto done;
            }
            tokenPtr += (tokenPtr->numComponents + 1);

            if (opDescPtr->numOperands == 2) {
                code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
                if (code != TCL_OK) {
                  goto done;
                }
                tokenPtr += (tokenPtr->numComponents + 1);
            }
            TclEmitOpcode(opDescPtr->instruction, envPtr);
            infoPtr->hasOperators = 1;
            break;
          }
          
          /*
           * The operator requires special treatment, and is either
           * "+" or "-", or one of "&&", "||" or "?".
           */
          
          switch (opIndex) {
              case OP_PLUS:
              case OP_MINUS:
                tokenPtr++;
                code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
                if (code != TCL_OK) {
                  goto done;
                }
                tokenPtr += (tokenPtr->numComponents + 1);
                
                /*
                 * Check whether the "+" or "-" is unary.
                 */
                
                afterSubexprPtr = exprTokenPtr
                      + exprTokenPtr->numComponents+1;
                if (tokenPtr == afterSubexprPtr) {
                  TclEmitOpcode(((opIndex==OP_PLUS)?
                          INST_UPLUS : INST_UMINUS),
                          envPtr);
                  break;
                }
                
                /*
                 * The "+" or "-" is binary.
                 */
                
                code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
                if (code != TCL_OK) {
                  goto done;
                }
                tokenPtr += (tokenPtr->numComponents + 1);
                TclEmitOpcode(((opIndex==OP_PLUS)? INST_ADD : INST_SUB),
                      envPtr);
                break;

              case OP_LAND:
              case OP_LOR:
                code = CompileLandOrLorExpr(exprTokenPtr, opIndex,
                      infoPtr, envPtr, &endPtr);
                if (code != TCL_OK) {
                  goto done;
                }
                tokenPtr = endPtr;
                break;
                  
              case OP_QUESTY:
                code = CompileCondExpr(exprTokenPtr, infoPtr,
                      envPtr, &endPtr);
                if (code != TCL_OK) {
                  goto done;
                }
                tokenPtr = endPtr;
                break;
                
            default:
                panic("CompileSubExpr: unexpected operator %d requiring special treatment\n",
                    opIndex);
          } /* end switch on operator requiring special treatment */
          infoPtr->hasOperators = 1;
          break;

        default:
          panic("CompileSubExpr: unexpected token type %d\n",
                  tokenPtr->type);
    }

    /*
     * Verify that the subexpression token had the required number of
     * subtokens: that we've advanced tokenPtr just beyond the
     * subexpression's last token. For example, a "*" subexpression must
     * contain the tokens for exactly two operands.
     */
    
    if (tokenPtr != (exprTokenPtr + exprTokenPtr->numComponents+1)) {
      LogSyntaxError(infoPtr);
      code = TCL_ERROR;
    }
    
    done:
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * CompileLandOrLorExpr --
 *
 *    This procedure compiles a Tcl logical and ("&&") or logical or
 *    ("||") subexpression.
 *
 * Results:
 *    The return value is TCL_OK on a successful compilation and TCL_ERROR
 *    on failure. If TCL_OK is returned, a pointer to the token just after
 *    the last one in the subexpression is stored at the address in
 *    endPtrPtr. If TCL_ERROR is returned, then the interpreter's result
 *    contains an error message.
 *
 * Side effects:
 *    Adds instructions to envPtr to evaluate the expression at runtime.
 *
 *----------------------------------------------------------------------
 */

static int
CompileLandOrLorExpr(exprTokenPtr, opIndex, infoPtr, envPtr, endPtrPtr)
    Tcl_Token *exprTokenPtr;   /* Points to TCL_TOKEN_SUB_EXPR token
                          * containing the "&&" or "||" operator. */
    int opIndex;         /* A code describing the expression
                          * operator: either OP_LAND or OP_LOR. */
    ExprInfo *infoPtr;         /* Describes the compilation state for the
                          * expression being compiled. */
    CompileEnv *envPtr;        /* Holds resulting instructions. */
    Tcl_Token **endPtrPtr;     /* If successful, a pointer to the token
                          * just after the last token in the
                          * subexpression is stored here. */
{
    JumpFixup shortCircuitFixup; /* Used to fix up the short circuit jump
                          * after the first subexpression. */
    JumpFixup lhsTrueFixup, lhsEndFixup;
                         /* Used to fix up jumps used to convert the
                          * first operand to 0 or 1. */
    Tcl_Token *tokenPtr;
    int dist, code;
    int savedStackDepth = envPtr->currStackDepth;

    /*
     * Emit code for the first operand.
     */

    tokenPtr = exprTokenPtr+2;
    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
      goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);

    /*
     * Convert the first operand to the result that Tcl requires:
     * "0" or "1". Eventually we'll use a new instruction for this.
     */
    
    TclEmitForwardJump(envPtr, TCL_TRUE_JUMP, &lhsTrueFixup);
    TclEmitPush(TclRegisterNewLiteral(envPtr, "0", 1), envPtr);
    TclEmitForwardJump(envPtr, TCL_UNCONDITIONAL_JUMP, &lhsEndFixup);
    dist = (envPtr->codeNext - envPtr->codeStart) - lhsTrueFixup.codeOffset;
    if (TclFixupForwardJump(envPtr, &lhsTrueFixup, dist, 127)) {
        badDist:
      panic("CompileLandOrLorExpr: bad jump distance %d\n", dist);
    }
    envPtr->currStackDepth = savedStackDepth;
    TclEmitPush(TclRegisterNewLiteral(envPtr, "1", 1), envPtr);
    dist = (envPtr->codeNext - envPtr->codeStart) - lhsEndFixup.codeOffset;
    if (TclFixupForwardJump(envPtr, &lhsEndFixup, dist, 127)) {
      goto badDist;
    }

    /*
     * Emit the "short circuit" jump around the rest of the expression.
     * Duplicate the "0" or "1" on top of the stack first to keep the
     * jump from consuming it.
     */

    TclEmitOpcode(INST_DUP, envPtr);
    TclEmitForwardJump(envPtr,
          ((opIndex==OP_LAND)? TCL_FALSE_JUMP : TCL_TRUE_JUMP),
          &shortCircuitFixup);

    /*
     * Emit code for the second operand.
     */

    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
      goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);

    /*
     * Emit a "logical and" or "logical or" instruction. This does not try
     * to "short- circuit" the evaluation of both operands, but instead
     * ensures that we either have a "1" or a "0" result.
     */

    TclEmitOpcode(((opIndex==OP_LAND)? INST_LAND : INST_LOR), envPtr);

    /*
     * Now that we know the target of the forward jump, update it with the
     * correct distance.
     */

    dist = (envPtr->codeNext - envPtr->codeStart)
          - shortCircuitFixup.codeOffset;
    TclFixupForwardJump(envPtr, &shortCircuitFixup, dist, 127);
    *endPtrPtr = tokenPtr;

    done:
    envPtr->currStackDepth = savedStackDepth + 1;
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * CompileCondExpr --
 *
 *    This procedure compiles a Tcl conditional expression:
 *    condExpr ::= lorExpr ['?' condExpr ':' condExpr]
 *
 * Results:
 *    The return value is TCL_OK on a successful compilation and TCL_ERROR
 *    on failure. If TCL_OK is returned, a pointer to the token just after
 *    the last one in the subexpression is stored at the address in
 *    endPtrPtr. If TCL_ERROR is returned, then the interpreter's result
 *    contains an error message.
 *
 * Side effects:
 *    Adds instructions to envPtr to evaluate the expression at runtime.
 *
 *----------------------------------------------------------------------
 */

static int
CompileCondExpr(exprTokenPtr, infoPtr, envPtr, endPtrPtr)
    Tcl_Token *exprTokenPtr;  /* Points to TCL_TOKEN_SUB_EXPR token
                         * containing the "?" operator. */
    ExprInfo *infoPtr;        /* Describes the compilation state for the
                         * expression being compiled. */
    CompileEnv *envPtr;       /* Holds resulting instructions. */
    Tcl_Token **endPtrPtr;    /* If successful, a pointer to the token
                         * just after the last token in the
                         * subexpression is stored here. */
{
    JumpFixup jumpAroundThenFixup, jumpAroundElseFixup;
                        /* Used to update or replace one-byte jumps
                         * around the then and else expressions when
                         * their target PCs are determined. */
    Tcl_Token *tokenPtr;
    int elseCodeOffset, dist, code;
    int savedStackDepth = envPtr->currStackDepth;

    /*
     * Emit code for the test.
     */

    tokenPtr = exprTokenPtr+2;
    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
      goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);
    
    /*
     * Emit the jump to the "else" expression if the test was false.
     */
    
    TclEmitForwardJump(envPtr, TCL_FALSE_JUMP, &jumpAroundThenFixup);

    /*
     * Compile the "then" expression. Note that if a subexpression is only
     * a primary, we need to try to convert it to numeric. We do this to
     * support Tcl's policy of interpreting operands if at all possible as
     * first integers, else floating-point numbers.
     */

    infoPtr->hasOperators = 0;
    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
      goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);
    if (!infoPtr->hasOperators) {
      TclEmitOpcode(INST_TRY_CVT_TO_NUMERIC, envPtr);
    }

    /*
     * Emit an unconditional jump around the "else" condExpr.
     */
    
    TclEmitForwardJump(envPtr, TCL_UNCONDITIONAL_JUMP,
          &jumpAroundElseFixup);

    /*
     * Compile the "else" expression.
     */

    envPtr->currStackDepth = savedStackDepth;
    elseCodeOffset = (envPtr->codeNext - envPtr->codeStart);
    infoPtr->hasOperators = 0;
    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
      goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);
    if (!infoPtr->hasOperators) {
      TclEmitOpcode(INST_TRY_CVT_TO_NUMERIC, envPtr);
    }

    /*
     * Fix up the second jump around the "else" expression.
     */

    dist = (envPtr->codeNext - envPtr->codeStart)
          - jumpAroundElseFixup.codeOffset;
    if (TclFixupForwardJump(envPtr, &jumpAroundElseFixup, dist, 127)) {
      /*
       * Update the else expression's starting code offset since it
       * moved down 3 bytes too.
       */
      
      elseCodeOffset += 3;
    }
      
    /*
     * Fix up the first jump to the "else" expression if the test was false.
     */
    
    dist = (elseCodeOffset - jumpAroundThenFixup.codeOffset);
    TclFixupForwardJump(envPtr, &jumpAroundThenFixup, dist, 127);
    *endPtrPtr = tokenPtr;

    done:
    envPtr->currStackDepth = savedStackDepth + 1;
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * CompileMathFuncCall --
 *
 *    This procedure compiles a call on a math function in an expression:
 *    mathFuncCall ::= funcName '(' [condExpr {',' condExpr}] ')'
 *
 * Results:
 *    The return value is TCL_OK on a successful compilation and TCL_ERROR
 *    on failure. If TCL_OK is returned, a pointer to the token just after
 *    the last one in the subexpression is stored at the address in
 *    endPtrPtr. If TCL_ERROR is returned, then the interpreter's result
 *    contains an error message.
 *
 * Side effects:
 *    Adds instructions to envPtr to evaluate the math function at
 *    runtime.
 *
 *----------------------------------------------------------------------
 */

static int
CompileMathFuncCall(exprTokenPtr, funcName, infoPtr, envPtr, endPtrPtr)
    Tcl_Token *exprTokenPtr;  /* Points to TCL_TOKEN_SUB_EXPR token
                         * containing the math function call. */
    CONST char *funcName;     /* Name of the math function. */
    ExprInfo *infoPtr;        /* Describes the compilation state for the
                         * expression being compiled. */
    CompileEnv *envPtr;       /* Holds resulting instructions. */
    Tcl_Token **endPtrPtr;    /* If successful, a pointer to the token
                         * just after the last token in the
                         * subexpression is stored here. */
{
    Tcl_Interp *interp = infoPtr->interp;
    Interp *iPtr = (Interp *) interp;
    MathFunc *mathFuncPtr;
    Tcl_HashEntry *hPtr;
    Tcl_Token *tokenPtr, *afterSubexprPtr;
    int code, i;

    /*
     * Look up the MathFunc record for the function.
     */

    code = TCL_OK;
    hPtr = Tcl_FindHashEntry(&iPtr->mathFuncTable, funcName);
    if (hPtr == NULL) {
      Tcl_AppendStringsToObj(Tcl_GetObjResult(interp),
            "unknown math function \"", funcName, "\"", (char *) NULL);
      code = TCL_ERROR;
      goto done;
    }
    mathFuncPtr = (MathFunc *) Tcl_GetHashValue(hPtr);

    /*
     * If not a builtin function, push an object with the function's name.
     */

    if (mathFuncPtr->builtinFuncIndex < 0) {
      TclEmitPush(TclRegisterNewLiteral(envPtr, funcName, -1), envPtr);
    }

    /*
     * Compile any arguments for the function.
     */

    tokenPtr = exprTokenPtr+2;
    afterSubexprPtr = exprTokenPtr + (exprTokenPtr->numComponents + 1);
    if (mathFuncPtr->numArgs > 0) {
      for (i = 0;  i < mathFuncPtr->numArgs;  i++) {
          if (tokenPtr == afterSubexprPtr) {
            Tcl_ResetResult(interp);
            Tcl_AppendToObj(Tcl_GetObjResult(interp),
                    "too few arguments for math function", -1);
            code = TCL_ERROR;
            goto done;
          }
          code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
          if (code != TCL_OK) {
            goto done;
          }
          tokenPtr += (tokenPtr->numComponents + 1);
      }
      if (tokenPtr != afterSubexprPtr) {
          Tcl_ResetResult(interp);
          Tcl_AppendToObj(Tcl_GetObjResult(interp),
                "too many arguments for math function", -1);
          code = TCL_ERROR;
          goto done;
      } 
    } else if (tokenPtr != afterSubexprPtr) {
      Tcl_ResetResult(interp);
      Tcl_AppendToObj(Tcl_GetObjResult(interp),
            "too many arguments for math function", -1);
      code = TCL_ERROR;
      goto done;
    }
    
    /*
     * Compile the call on the math function. Note that the "objc" argument
     * count for non-builtin functions is incremented by 1 to include the
     * function name itself.
     */

    if (mathFuncPtr->builtinFuncIndex >= 0) { /* a builtin function */
      /*
       * Adjust the current stack depth by the number of arguments
       * of the builtin function. This cannot be handled by the 
       * TclEmitInstInt1 macro as the number of arguments is not
       * passed as an operand.
       */

      if (envPtr->maxStackDepth < envPtr->currStackDepth) {
          envPtr->maxStackDepth = envPtr->currStackDepth;
      }
      TclEmitInstInt1(INST_CALL_BUILTIN_FUNC1,
              mathFuncPtr->builtinFuncIndex, envPtr);
      envPtr->currStackDepth -= mathFuncPtr->numArgs;
    } else {
      TclEmitInstInt1(INST_CALL_FUNC1, (mathFuncPtr->numArgs+1), envPtr);
    }
    *endPtrPtr = afterSubexprPtr;

    done:
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * LogSyntaxError --
 *
 *    This procedure is invoked after an error occurs when compiling an
 *    expression. It sets the interpreter result to an error message
 *    describing the error.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Sets the interpreter result to an error message describing the
 *    expression that was being compiled when the error occurred.
 *
 *----------------------------------------------------------------------
 */

static void
LogSyntaxError(infoPtr)
    ExprInfo *infoPtr;        /* Describes the compilation state for the
                         * expression being compiled. */
{
    int numBytes = (infoPtr->lastChar - infoPtr->expr);
    char buffer[100];

    sprintf(buffer, "syntax error in expression \"%.*s\"",
          ((numBytes > 60)? 60 : numBytes), infoPtr->expr);
    Tcl_ResetResult(infoPtr->interp);
    Tcl_AppendStringsToObj(Tcl_GetObjResult(infoPtr->interp),
          buffer, (char *) NULL);
}

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