Source code of Windows XP (NT5)
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/*****************************************************************************
*
* eval.c
*
* Arithmetical evaluation.
*
*****************************************************************************/
#include "m4.h"
/*****************************************************************************
*
* First, a warm-up: Increment and decrement.
*
*****************************************************************************/
/*****************************************************************************
*
* opIncr
* opDecr
*
* Returns the value of its argument, augmented or diminished by unity.
* The extra ptokNil covers us in the case where $# is zero.
*
*****************************************************************************/
void STDCALL
opAddItokDat(ARGV argv, DAT dat)
{
AT at = atTraditionalPtok(ptokArgv(1));
#ifdef STRICT_M4
if (ctokArgv != 1) {
Warn("wrong number of arguments to %P", ptokArgv(0));
}
#endif
PushAt(at+dat);
}
DeclareOp(opIncr)
{
opAddItokDat(argv, 1);
}
DeclareOp(opDecr)
{
opAddItokDat(argv, -1);
}
/*****************************************************************************
*
* Now the gross part: Eval.
*
* Expression evaluation is performed by a parser which is a mix of
* shift-reduce and recursive-descent. (Worst of both worlds.)
*
* The precedence table for our expression language reads
*
* (...) grouping > primary
* + - unary
* ** exponentiation
* * / % multiplicative
* + - additive
* << >> shift
* == != > >= < <= relational
* ! logical-negate
* ~ bit-negate
* & bit-and
* ^ bit-xor
* | bit-or
* && logical-and
* || logical-or
*
*
* COMPAT -- AT&T style uses ^ for exponentiation; we use it for xor
*
* NOTE: "the rest is bogus" went the original comment. I forget what
* I meant by that.
*
* The precedence table for the C-style expression language reads
*
* (...) grouping \ primary
* + - ~ ! unary /
* * / % multiplative \
* + - additive \
* << >> shift |
* < > <= >= relational |
* == != equality \ secondary
* & bit-and /
* ^ bit-xor |
* | bit-or |
* && logical-and /
* || logical-or /
* ? : ternary > tertiary
*
* Recursive descent is performed on the primary/secondary/tertiary
* scale, but shift-reduce is performed within the secondary phase.
*
* The reason is that the operators in the secondary phase are
* (1) binary, and (2) non-recursive. These two properties
* make shift-reduce easy to implement.
*
* Primaries are recursive, so they are easier to implement in
* recursive-descent. Tertiaries would clog up the shift-reduce
* grammar, so they've been moved to recursive-descent as well.
*
*****************************************************************************/
/*****************************************************************************
*
* EachEop
*
* Before calling this macro, define the following macros, each of
* which will be called with three arguments,
*
* nm = operator name as a C identifier (e.g., "Add")
* op = operator name as a bare token (e.g., "+")
* cb = length of operator name
*
* The macros should be
*
* x1 -- for native C unary operators
* x1a -- for native C unary operators which have binary aliases
* x2 -- for native C binary operators
* x2a -- for native C binary operators which have unary aliases
* x2n -- for non-native C binary operators
* xp -- for phantom operators,
* in which case op and cb are useless
*
* The order in which operators appear is important for the purpose
* of tokenization. Longer operators must precede shorter ones.
*
*****************************************************************************/
#define EachEop() \
x2(Shl, <<, 2) \
x2(Shr, >>, 2) \
x2(Le, <=, 2) \
x2(Ge, >=, 2) \
x2(Eq, ==, 2) \
x2(Ne, !=, 2) \
x2(Land, &&, 2) \
x2(Lor, ||, 2) \
x2n(Exp, **, 2) \
x2(Mul, *, 1) \
x2(Div, /, 1) \
x2(Mod, %, 1) \
x2a(Add, +, 1) /* These two must be */ \
x2a(Sub, -, 1) /* in exactly this order */ \
x2(Lt, <, 1) \
x2(Gt, >, 1) \
x2(Band, &, 1) \
x2(Bxor, ^, 1) \
x2(Bor, |, 1) \
x1(Lnot, !, 1) \
x1(Bnot, ~, 1) \
x1a(Plu, +, x) /* These two must be */ \
x1a(Neg, -, x) /* in exactly this order */ \
xp(Flush, @, 0) \
xp(Boe, @, 0) \
/*****************************************************************************
*
* MakeEop
*
* Each binary operator has a handler which returns the combined
* value.
*
* Each unary operator has a handler which returns the operator
* applied to its single argument.
*
* All the operators are C native, except for Exp, which is handled
* directly.
*
*****************************************************************************/
typedef AT (STDCALL *EOP1)(AT at);
typedef AT (STDCALL *EOP2)(AT a, AT b);
#define x1(nm, op, cb) AT STDCALL at##nm##At(AT at) { return op at; }
#define x1a(nm, op, cb) AT STDCALL at##nm##At(AT at) { return op at; }
#define x2(nm, op, cb) AT STDCALL at##nm##AtAt(AT a, AT b) { return a op b; }
#define x2a(nm, op, cb) AT STDCALL at##nm##AtAt(AT a, AT b) { return a op b; }
#define x2n(nm, op, cb)
#define xp(nm, op, cb)
EachEop()
#undef x1
#undef x1a
#undef x2
#undef x2a
#undef x2n
#undef xp
/*****************************************************************************
*
* atExpAtAt
*
* Implement the exponentiation operator.
*
* QUIRK! AT&T returns 1 if $2 < 0. GNU raises an error.
* I side with AT&T on this, only out of laziness.
*
*****************************************************************************/
AT STDCALL
atExpAtAt(AT a, AT b)
{
AT at = 1;
while (b > 0) {
if (b & 1) {
at = at * a;
}
a = a * a;
b = b / 2;
}
return at;
}
TOK tokExpr; /* Current expression context */
/*****************************************************************************
*
* MakeEopTab
*
* Table of operators and operator precedence. Each entry in the
* table contains the name, length, handler, precedence, and
* flags that describe what kind of operator it is.
*
* Items are listed in precedence order here; the EachBop will
* emit the table corrctly.
*
*****************************************************************************/
typedef enum EOPFL {
eopflUn = 1,
eopflBin = 2,
eopflAmb = 4,
} EOPFL;
typedef UINT PREC; /* Operator precedence */
typedef struct EOPI {
PTCH ptch;
CTCH ctch;
union {
EOP1 eop1;
EOP2 eop2;
} u;
PREC prec;
EOPFL eopfl;
} EOPI, *PEOPI;
#define MakeEopi(nm, ctch, pfn, prec, eopfl) \
{ TEXT(nm), ctch, { (EOP1)pfn }, prec, eopfl },
enum {
m4precNeg = 14, m4precPlu = 14,
m4precExp = 13,
m4precMul = 12, m4precDiv = 12, m4precMod = 12,
m4precAdd = 11, m4precSub = 11,
m4precShl = 10, m4precShr = 10,
m4precEq = 9, m4precNe = 9,
m4precGt = 9, m4precGe = 9,
m4precLt = 9, m4precLe = 9,
m4precLnot = 8,
m4precBnot = 7,
m4precBand = 6,
m4precBxor = 5,
m4precBor = 4,
m4precLand = 3,
m4precLor = 2,
m4precFlush = 1, /* Flushing out everything but Boe */
m4precBoe = 0, /* Beginning-of-expression */
};
#define x1(nm, op, cb) static TCH rgtch##nm[cb] = #op;
#define x1a(nm, op, cb)
#define x2(nm, op, cb) static TCH rgtch##nm[cb] = #op;
#define x2a(nm, op, cb) static TCH rgtch##nm[cb] = #op;
#define x2n(nm, op, cb) static TCH rgtch##nm[cb] = #op;
#define xp(nm, op, cb)
EachEop()
#undef x1
#undef x1a
#undef x2
#undef x2a
#undef x2n
#undef xp
#define x1(nm, op, cb) MakeEopi(rgtch##nm, cb, at##nm##At, m4prec##nm, eopflUn)
#define x1a(nm, op, cb) MakeEopi(0, 0, at##nm##At, m4prec##nm, eopflUn)
#define x2(nm, op, cb) MakeEopi(rgtch##nm, cb, at##nm##AtAt, m4prec##nm, eopflBin)
#define x2a(nm, op, cb) MakeEopi(rgtch##nm, cb, at##nm##AtAt, m4prec##nm, eopflAmb + eopflBin) /* initially bin */
#define x2n(nm, op, cb) MakeEopi(rgtch##nm, cb, at##nm##AtAt, m4prec##nm, eopflBin)
#define xp(nm, op, cb) MakeEopi(0, 0, 0, m4prec##nm, 0)
EOPI rgeopi[] = {
EachEop()
};
#undef x1
#undef x1a
#undef x2
#undef x2a
#undef x2n
#undef xp
#define x1(nm, op, cb) ieopi##nm,
#define x1a(nm, op, cb) ieopi##nm,
#define x2(nm, op, cb) ieopi##nm,
#define x2a(nm, op, cb) ieopi##nm,
#define x2n(nm, op, cb) ieopi##nm,
#define xp(nm, op, cb) ieopi##nm,
typedef enum IEOPI {
EachEop()
ieopMax,
} IEOPI;
#undef x1
#undef x1a
#undef x2
#undef x2a
#undef x2n
#define peopiBoe (&rgeopi[ieopiBoe])
#define peopiFlush (&rgeopi[ieopiFlush])
/*****************************************************************************
*
* fPrimary, fSecondary, fTertiary
*
* Forward declarations for the recursive-descent parser.
*
* Each parses a token/expression of the appropriate class
* and leaves it on the top of the expression stack, or
* returns 0 if the value could not be parsed.
*
*****************************************************************************/
F STDCALL fPrimary(void);
F STDCALL fSecondary(void);
#define fTertiary fSecondary
/*****************************************************************************
*
* Cells
*
* The expression stack consists of structures which, for lack of
* a better name, are called `cells'. Each cell can hold either
* an expression operator or an integer, distinguished by the fEopi
* field.
*
* In keeping with parser terminology, the act of pushing something
* onto the stack is called `shifting'. Collapsing objects is called
* `reducing'.
*
*****************************************************************************/
typedef struct CELL {
F fEopi;
union {
PEOPI peopi;
AT at;
} u;
} CELL, *PCELL;
typedef UINT CCELL, ICELL;
PCELL rgcellEstack; /* The expression stack */
PCELL pcellMax; /* End of the stack */
PCELL pcellCur; /* Next free cell */
INLINE PCELL
pcellTos(ICELL icell)
{
Assert(pcellCur - 1 - icell >= rgcellEstack);
return pcellCur - 1 - icell;
}
/*****************************************************************************
*
* Stack munging
*
* Quickie routines that poke at the top-of-stack.
*
*****************************************************************************/
INLINE F fWantOp(void) { return !pcellTos(1)->fEopi; }
INLINE F fOpTos(ICELL icell) { return pcellTos(icell)->fEopi; }
INLINE PEOPI
peopiTos(ICELL icell)
{
Assert(fOpTos(icell));
return pcellTos(icell)->u.peopi;
}
INLINE AT
atTos(ICELL icell)
{
Assert(!fOpTos(icell));
return pcellTos(icell)->u.at;
}
INLINE F fBinTos(ICELL icell) { return peopiTos(icell)->eopfl & eopflBin; }
INLINE F fUnTos(ICELL icell) { return peopiTos(icell)->eopfl & eopflUn; }
INLINE F fAmbTos(ICELL icell) { return peopiTos(icell)->eopfl & eopflAmb; }
INLINE PREC precTos(ICELL icell) { return peopiTos(icell)->prec; }
INLINE void
UnFromAmb(ICELL icell)
{
Assert(fOpTos(icell));
pcellTos(icell)->u.peopi += (ieopiPlu - ieopiAdd);
}
/*****************************************************************************
*
* ShiftCell
*
* Shift a cell onto the expression stack.
*
* QShiftCell shifts in a cell assuming that the stack is already
* big enough to handle it.
*
*****************************************************************************/
void STDCALL
QShiftCell(UINT_PTR uiObj, F fEopi)
{
Assert(pcellCur < pcellMax);
pcellCur->fEopi = fEopi;
if (fEopi) {
pcellCur->u.peopi = (PEOPI)uiObj;
} else {
pcellCur->u.at = (INT)uiObj;
}
pcellCur++;
}
void STDCALL
ShiftCell(UINT_PTR uiObj, F fEopi)
{
if (pcellCur >= pcellMax) {
CCELL ccell = (CCELL)(pcellMax - rgcellEstack + 128); /* Should be enough */
rgcellEstack = pvReallocPvCb(rgcellEstack, ccell * sizeof(CELL));
pcellCur = rgcellEstack + ccell - 128;
pcellMax = rgcellEstack + ccell;
}
QShiftCell(uiObj, fEopi);
}
#define ShiftPeopi(peopi) ShiftCell((UINT_PTR)(peopi), 1)
#define ShiftAt(at) ShiftCell((UINT_PTR)(at), 0)
#define QShiftPeopi(peopi) QShiftCell((UINT_PTR)(peopi), 1)
#define QShiftAt(at) QShiftCell((UINT_PTR)(at), 0)
#define Drop(icell) (pcellCur -= (icell))
/*****************************************************************************
*
* ReducePrec
*
* Reduce until everything with higher precedence has been cleaned off.
*
* Tos(0) should be a fresh operator.
* Everything underneath should be a valid partial evaluation.
*
*****************************************************************************/
void STDCALL
Reduce(void)
{
PEOPI peopi;
Assert(fOpTos(0)); /* Tos(0) should be an op */
Assert(!fOpTos(1)); /* Tos(1) should be an int */
Assert(fOpTos(2)); /* Tos(2) should be an op */
peopi = peopiTos(0); /* Save this */
Drop(1); /* before we drop it */
while (precTos(1) > peopi->prec) {
AT at;
if (fUnTos(1)) {
at = peopiTos(1)->u.eop1(atTos(0));
Drop(2); /* Drop the op and the arg */
} else {
Assert(fBinTos(1));
Assert(!fOpTos(2));
at = peopiTos(1)->u.eop2(atTos(2), atTos(0));
Drop(3); /* Drop the op and two args */
}
QShiftAt(at); /* Shift the answer back on */
Assert(!fOpTos(0)); /* Tos(0) should be an int */
Assert(fOpTos(1)); /* Tos(1) should be an op */
}
QShiftPeopi(peopi); /* Restore the original op */
}
/*****************************************************************************
*
* fPrimary
*
* Parse the next expression token and shift it onto the expression
* stack. Zero is returned if there is no next token, or the token
* is invalid.
*
* Here is where parenthesized expressions are handled, in a
* recursive-descent manner.
*
* Ambiguous operators (ones which can be either unary or binary)
* are returned as binary.
*
*****************************************************************************/
F STDCALL
fPrimary(void)
{
SkipWhitePtok(&tokExpr); /* Skip leading whitespace */
/*
* First see if we can find an operator.
*/
{
PEOPI peopi;
for (peopi = rgeopi; peopi < &rgeopi[ieopiPlu]; peopi++) {
if (peopi->ctch <= ctchSPtok(&tokExpr) &&
fEqPtchPtchCtch(ptchPtok(&tokExpr), peopi->ptch,
peopi->ctch)) {
EatHeadPtokCtch(&tokExpr, peopi->ctch); /* Eat the op */
ShiftPeopi(peopi);
return 1;
}
}
}
/*
* Didn't find an operator. Look for an integer.
*/
{
AT at;
if (fEvalPtokPat(&tokExpr, &at)) {
ShiftAt(at);
return 1;
}
}
/*
* Not an integer either. Maybe a parenthesized expression.
*/
{
if (ptchPtok(&tokExpr)[0] == '(') {
EatHeadPtokCtch(&tokExpr, 1); /* Eat the paren */
if (fTertiary()) { /* Leaves answer on top of stack */
if (ptchPtok(&tokExpr)[0] == ')') {
EatHeadPtokCtch(&tokExpr, 1); /* Eat the paren */
return 1;
} else {
return 0;
}
} else {
return 0; /* Trouble down below */
}
}
}
/*
* Unrecognized token. Return failure.
*/
return 0;
}
/*****************************************************************************
*
* fSecondary
*
* Parse an expression from the expression stream, leaving the
* result on the top of the expression stack.
*
*****************************************************************************/
F STDCALL
fSecondary(void)
{
ShiftPeopi(peopiBoe); /* Beginning-of-expression marker */
while (fPrimary()) {
if (fWantOp()) {
if (fOpTos(0)) {
if (fBinTos(0)) {
Reduce();
} else {
return 0; /* Unary operator unexpected */
}
} else {
return 0; /* Integer unexpected */
}
} else { /* Integer expected */
if (fOpTos(0)) {
if (fAmbTos(0)) {
UnFromAmb(0); /* Disambiguify */
; /* Unary operator already shifted */
} else if (fUnTos(0)) {
; /* Unary operator already shifted */
} else {
return 0; /* Binary operator unexpected */
}
} else {
; /* Integer already shifted */
}
}
}
if (fOpTos(0)) {
return 0; /* Ended in partial expression */
}
{
AT at;
ShiftPeopi(peopiFlush); /* Flush out the rest of the expr */
Reduce(); /* to get a single number back */
Assert(peopiTos(0) == peopiFlush);
at = atTos(1);
Assert(peopiTos(2) == peopiBoe); /* Should be back to start */
Drop(3);
ShiftAt(at);
}
return 1;
}
/*****************************************************************************
*
* opEval
*
* Evaluate the first expr.
*
* QUIRK! AT&T m4 considers a consisting entirely of whitespace to
* evaluate to zero. (Probably due to a default accumulator in the
* initial state of the evaluator.) GNU considers it an error.
* I side with GNU on this one.
*
* QUIRK! If a negative width is passed, AT&T silently treats it
* as zero. GNU raises an error. I side with A&T out of laziness.
*
* QUIRK! If a width greater than around 8000 is passed, AT&T
* silently treats it as zero. GNU uses the full value. I side
* with GNU on this one.
*
*****************************************************************************/
DeclareOp(opEval)
{
if (ctokArgv) {
SetStaticPtokPtchCtch(&tokExpr, ptchArgv(1), ctchArgv(1));
D(tokExpr.tsfl |= tsflScratch);
if (fTertiary()) {
PushAtRadixCtch(atTos(0), (unsigned)atTraditionalPtok(ptokArgv(2)),
ctokArgv >= 3 ? atTraditionalPtok(ptokArgv(3)) :0);
Drop(1);
Assert(pcellCur == rgcellEstack);
} else {
TOK tokPre;
SetStaticPtokPtchCtch(&tokPre, ptchArgv(1),
ctchArgv(1) - ctchSPtok(&tokExpr));
Die("Expression error at %P <<error>> %P", &tokPre, &tokExpr);
}
}
}