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parser.c
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/* parser --- C parser 2022-07-31 */
/* Copyright (c) 2022 John Honniball. All rights reserved */
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include "codegen.h"
#include "lexical.h"
//#define LEX_TESTER
#define MAXCASES (512) // Maximum number of case labels in a 'switch'
struct StringConstant Strings[64];
static int NextStr = 0;
void initialise(void);
void parse(const char fname[]);
void parser(void);
int ParseDeclaration(struct Token *tok);
void ParseFunctionBody(struct Token *tok, const struct Symbol *const fn);
void ParseStatement(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int breakLabel, const int continueLabel);
void ParseReturn(struct Token *tok, const struct Symbol *const fn, const int returnLabel);
void ParseCompoundStatement(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int breakLabel, const int continueLabel);
void ParseIf(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int breakLabel, const int continueLabel);
void ParseExpression(struct Token *tok);
void ParseDo(struct Token *tok, const struct Symbol *const fn, const int returnLabel);
void ParseBreak(struct Token *tok, const int breakLabel);
void ParseContinue(struct Token *tok, const int continueLabel);
void ParseGoto(struct Token *tok);
void ParseWhile(struct Token *tok, const struct Symbol *const fn, const int returnLabel);
void ParseFor(struct Token *tok, const struct Symbol *const fn, const int returnLabel);
void ParseSwitch(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int continueLabel);
void ParseSemi(struct Token *tok, const char location[]);
bool ParseConstIntExpr(struct Token *tok, int *value, int *type);
int main(const int argc, const char *argv[])
{
int i;
initialise();
for (i = 1; i < argc; i++) {
if (argv[i][0] == '-') {
switch (argv[i][1]) {
case 'T':
SetTokenTraceFlag(true);
break;
case 'S':
SetSyntaxTraceFlag(true);
break;
default:
fprintf(stderr, "Usage: %s [-T] [-S] <filename>\n", argv[0]);
exit(EXIT_FAILURE);
break;
}
}
else {
parse(argv[i]);
}
}
return (0);
}
/* initialise --- call all module initialisation functions */
void initialise(void)
{
CodeGenInit();
LexicalInit();
SymTabInit();
}
/* parse --- open, parse and translate a single source code file */
void parse(const char fname[])
{
if (OpenSourceFile(fname) == false)
return;
if (OpenAssemblerFile(fname) == false) {
CloseSourceFile();
return;
}
parser();
CloseAssemblerFile();
CloseSourceFile();
}
/* parser --- parse and translate a single compilation-unit */
void parser(void)
{
struct Token tok;
#ifdef LEX_TESTER
while (GetToken(&tok) != TEOF)
PrintToken(&tok);
#else
GetToken(&tok);
while (ParseDeclaration(&tok) != EOF)
;
#endif
}
/* ParseDeclaration --- parse a top-level declaration */
int ParseDeclaration(struct Token *tok)
{
struct Symbol sym;
int type;
int iValue;
int iType;
int paramSize = 0;
type = 0;
sym.name[0] = '\0';
sym.storageClass = SCEXTERN;
sym.type = T_INT;
sym.pLevel = 0;
sym.label = NOLABEL;
sym.fpOffset = 0;
sym.readOnly = false;
switch (tok->token) {
case TEOF:
return (EOF);
case TSEMI:
GetToken(tok);
break;
case TVOID:
case TINT:
case TCHAR:
case TFLOAT:
case TDOUBLE:
PrintSyntax("<type>");
type = tok->token;
GetToken(tok);
while (tok->token == TSTAR) {
PrintSyntax("<'*'>");
sym.pLevel++;
GetToken(tok);
}
if (tok->token == TID) {
PrintSyntax("<id:%s>", tok->str);
strncpy(sym.name, tok->str, MAXNAME);
GetToken(tok);
}
else {
Error("Missing identifier in declaration");
}
switch (tok->token) {
case TASSIGN: // Scalar initialiser
PrintSyntax("<'='>");
GetToken(tok);
if (sym.pLevel == 0) {
switch (type) {
case TCHAR:
sym.type = T_CHAR;
if (ParseConstIntExpr(tok, &iValue, &iType)) {
EmitExternScalar(&sym, iValue, 0.0);
}
else {
Error("Expected integer constant after '='");
}
break;
case TINT:
sym.type = T_INT;
if (ParseConstIntExpr(tok, &iValue, &iType)) {
EmitExternScalar(&sym, iValue, 0.0);
}
else {
Error("Expected integer constant after '='");
}
break;
case TFLOAT:
sym.type = T_FLOAT;
EmitExternScalar(&sym, 0, tok->fValue);
GetToken(tok);
break;
case TDOUBLE:
sym.type = T_DOUBLE;
EmitExternScalar(&sym, 0, tok->fValue);
GetToken(tok);
break;
}
}
else {
EmitExternScalar(&sym, tok->iValue, 0.0);
GetToken(tok);
}
if (AddExternSymbol(&sym) == false) {
Error("Symbol '%s' is already declared", sym.name);
}
ParseSemi(tok, "in declaration");
break;
case TOSQBRK: // Array
PrintSyntax("[");
GetToken(tok);
if (ParseConstIntExpr(tok, &iValue, &iType)) {
if (tok->token == TCSQBRK) {
PrintSyntax("]");
GetToken(tok);
}
else {
Error("Expected ']' after array dimension");
}
}
else {
Error("Expected integer constant after '['");
}
ParseSemi(tok, "in array declaration");
break;
case TOPAREN: // Function
PrintSyntax("(");
GetToken(tok);
paramSize = 0;
// Function's formal parameters
while ((tok->token == TINT) || (tok->token == TCHAR) ||
(tok->token == TFLOAT) || (tok->token == TDOUBLE) ||
(tok->token == TVOID) || (tok->token == TCONST)) {
struct Symbol param;
int type;
PrintSyntax("<formal_parameter>");
param.storageClass = SCAUTO;
param.name[0] = '\0';
param.type = T_INT;
param.pLevel = 0;
param.label = NOLABEL;
param.fpOffset = 0;
param.readOnly = false;
if (tok->token == TCONST) {
GetToken(tok);
param.readOnly = true;
}
type = tok->token; // Yikes, we're assuming that the next token is a valid type!
GetToken(tok);
if (type == TVOID) { // 'void' must be alone with no identifier following
break;
}
while (tok->token == TSTAR) {
PrintSyntax("<'*'>");
param.pLevel++;
GetToken(tok);
}
if (tok->token == TID) {
PrintSyntax("<id:%s>", tok->str);
strncpy(param.name, tok->str, MAXNAME);
if (param.pLevel == 0) {
switch (type) {
case TCHAR:
param.type = T_CHAR;
paramSize += 2;
break;
case TINT:
param.type = T_INT;
paramSize += 2;
break;
case TFLOAT:
param.type = T_FLOAT;
paramSize += 4;
break;
case TDOUBLE:
param.type = T_DOUBLE;
paramSize += 8;
break;
}
}
else {
param.type = T_INT;
paramSize += 2;
}
param.fpOffset = paramSize;
}
else {
Error("Expected identifier in parameter declaration");
}
AddLocalSymbol(¶m);
PrintSyntax("\n");
GetToken(tok);
if (tok->token == TCOMMA) {
GetToken(tok);
}
else if (tok->token != TCPAREN) {
Error("Missing comma in parameter list");
}
}
if (tok->token == TCPAREN) {
PrintSyntax(")");
if (sym.pLevel == 0) {
switch (type) {
case TVOID:
sym.type = T_VOID;
break;
case TCHAR:
sym.type = T_INT;
break;
case TINT:
sym.type = T_INT;
break;
case TFLOAT:
sym.type = T_FLOAT;
break;
case TDOUBLE:
sym.type = T_DOUBLE;
break;
}
}
else {
sym.type = T_INT;
}
}
else {
Error("Malformed function declaration");
}
GetToken(tok);
sym.readOnly = true;
if (AddExternSymbol(&sym) == false) {
// Functions may already have prototypes or K&R-style declarations
//Error("Symbol '%s' is already declared", sym.name);
}
if (tok->token == TOBRACE) {
PrintSyntax("<function_definition>\n");
ParseFunctionBody(tok, &sym);
}
else {
PrintSyntax("<function_prototype>");
ParseSemi(tok, "in function prototype");
}
sym.readOnly = false;
break;
case TSEMI: // Uninitialised scalar
GetToken(tok);
if (sym.pLevel == 0) {
switch (type) {
case TCHAR:
sym.type = T_CHAR;
EmitExternScalar(&sym, 0, 0.0);
break;
case TINT:
sym.type = T_INT;
EmitExternScalar(&sym, 0, 0.0);
break;
case TFLOAT:
sym.type = T_FLOAT;
EmitExternScalar(&sym, 0, 0.0);
break;
case TDOUBLE:
sym.type = T_DOUBLE;
EmitExternScalar(&sym, 0, 0.0);
break;
}
}
else {
sym.type = T_INT;
EmitExternScalar(&sym, 0, 0.0);
}
if (AddExternSymbol(&sym) == false) {
Error("Symbol '%s' is already declared", sym.name);
}
break;
default:
Error("Unexpected symbol '%s' in declaration", tok->str);
break;
}
break;
default:
Error("Unexpected symbol '%s' in declaration", tok->str);
break;
}
PrintSyntax("\n");
return (tok->token);
}
/* ParseFunctionBody --- parse the body of a function */
void ParseFunctionBody(struct Token *tok, const struct Symbol *const fn)
{
int autoSize = 0;
int nRegister = 0;
int i;
const int returnLabel = AllocLabel('R');
NextStr = 0;
GetToken(tok);
// Function's local variables
while ((tok->token == TINT) || (tok->token == TCHAR) ||
(tok->token == TFLOAT) || (tok->token == TDOUBLE) ||
(tok->token == TSTATIC) || (tok->token == TAUTO) ||
(tok->token == TREGISTER) ||(tok->token == TCONST)) {
struct Symbol sym;
int type;
bool isRegister = false;
PrintSyntax("<declaration>");
sym.storageClass = SCAUTO;
sym.name[0] = '\0';
sym.type = T_INT;
sym.pLevel = 0;
sym.label = NOLABEL;
sym.fpOffset = 0;
sym.readOnly = false;
if (tok->token == TSTATIC) { // Accept 'static' storage class
PrintSyntax("<static>");
GetToken(tok);
sym.storageClass = SCSTATIC;
}
else if (tok->token == TCONST) { // Accept 'const' attribute
PrintSyntax("<const>");
GetToken(tok);
sym.readOnly = true;
}
else if (tok->token == TAUTO) { // Ignore 'auto' storage class
PrintSyntax("<auto>");
GetToken(tok);
}
else if (tok->token == TREGISTER) { // Accept 'register' storage class
PrintSyntax("<register>");
GetToken(tok);
isRegister = true;
}
type = tok->token; // Yikes, we're assuming that the next token is a valid type!
GetToken(tok);
while (tok->token == TSTAR) {
PrintSyntax("<'*'>");
sym.pLevel++;
GetToken(tok);
}
// Decide whether to accept the 'register' storage class
if (isRegister && (sym.storageClass == SCAUTO)) {
if (((type == TCHAR) || (type == TINT)) && (nRegister < 1)) {
sym.storageClass = SCREGISTER;
nRegister++;
}
}
if (tok->token == TID) {
PrintSyntax("<id:%s>", tok->str);
strncpy(sym.name, tok->str, MAXNAME);
if (sym.storageClass == SCSTATIC) {
sym.label = AllocLabel('S');
if (sym.pLevel == 0) {
switch (type) {
case TCHAR:
sym.type = T_CHAR;
break;
case TINT:
sym.type = T_INT;
break;
case TFLOAT:
sym.type = T_FLOAT;
break;
case TDOUBLE:
sym.type = T_DOUBLE;
break;
}
}
else {
sym.type = T_INT;
}
EmitExternScalar(&sym, 0, 0.0);
}
else if (sym.storageClass == SCREGISTER) {
if (sym.pLevel == 0) {
switch (type) {
case TCHAR:
sym.type = T_CHAR;
break;
case TINT:
sym.type = T_INT;
break;
case TFLOAT:
sym.type = T_FLOAT;
break;
case TDOUBLE:
sym.type = T_DOUBLE;
break;
}
}
else {
sym.type = T_INT;
}
}
else {
if (sym.pLevel == 0) {
switch (type) {
case TCHAR:
sym.type = T_CHAR;
autoSize += 1;
break;
case TINT:
sym.type = T_INT;
autoSize += 2;
break;
case TFLOAT:
sym.type = T_FLOAT;
autoSize += 4;
break;
case TDOUBLE:
sym.type = T_DOUBLE;
autoSize += 8;
break;
}
}
else {
sym.type = T_INT;
autoSize += 2;
}
sym.fpOffset = -autoSize;
}
}
else {
Error("Expected identifier in local variable declaration");
}
AddLocalSymbol(&sym);
PrintSyntax("\n");
GetToken(tok);
ParseSemi(tok, "in local variable declaration");
}
// Function entry sequence
EmitFunctionEntry(fn->name, autoSize, nRegister);
// Function's executable code
while (tok->token != TCBRACE) {
ParseStatement(tok, fn, returnLabel, NOLABEL, NOLABEL);
}
GetToken(tok);
// Function exit sequence
EmitFunctionExit(returnLabel, nRegister);
for (i = 0; i < NextStr; i++) {
EmitStaticCharArray(&Strings[i], "<anon>");
}
NextStr = 0;
ForgetLocalSymbols();
}
/* ParseStatement --- parse a single statement */
void ParseStatement(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int breakLabel, const int continueLabel)
{
PrintSyntax("<statement> ");
switch (tok->token) {
case TRETURN:
ParseReturn(tok, fn, returnLabel);
break;
case TIF:
ParseIf(tok, fn, returnLabel, breakLabel, continueLabel);
break;
case TDO:
ParseDo(tok, fn, returnLabel);
break;
case TFOR:
ParseFor(tok, fn, returnLabel);
break;
case TWHILE:
ParseWhile(tok, fn, returnLabel);
break;
case TGOTO:
ParseGoto(tok);
break;
case TCONTINUE:
ParseContinue(tok, continueLabel);
break;
case TBREAK:
ParseBreak(tok, breakLabel);
break;
case TSWITCH:
ParseSwitch(tok, fn, returnLabel, continueLabel);
break;
case TOBRACE:
ParseCompoundStatement(tok, fn, returnLabel, breakLabel, continueLabel);
break;
default:
ParseExpression(tok);
ParseSemi(tok, "after expression");
break;
}
}
/* ParseReturn --- parse a 'return' statement */
void ParseReturn(struct Token *tok, const struct Symbol *const fn, const int returnLabel)
{
PrintSyntax("<return> ");
GetToken(tok);
if (tok->token == TSEMI) {
PrintSyntax("\n");
if (fn->type != T_VOID) {
Error("non-void function %s returns no value", fn->name);
}
}
else {
ParseExpression(tok);
if (fn->type == T_VOID) {
Error("void function %s returns a value", fn->name);
}
}
EmitJump(returnLabel, "return");
ParseSemi(tok, "at end of 'return'");
}
/* ParseCompoundStatement --- parse a compound statement */
void ParseCompoundStatement(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int breakLabel, const int continueLabel)
{
PrintSyntax("<compound_statement>\n");
GetToken(tok);
while (tok->token != TCBRACE) {
ParseStatement(tok, fn, returnLabel, breakLabel, continueLabel);
}
GetToken(tok); /* Skip the closing curly bracket */
}
/* ParseIf --- parse an 'if' statement */
void ParseIf(struct Token *tok, const struct Symbol *const fn, const int returnLabel, const int breakLabel, const int continueLabel)
{
const int elseLabel = AllocLabel('E');
PrintSyntax("<if> ");
GetToken(tok);
if (tok->token == TOPAREN) {
GetToken(tok);
ParseExpression(tok);
if (tok->token == TCPAREN) {
EmitCompareIntConstant(0, "if: test");
EmitBranchIfEqual(elseLabel, "if: branch");
GetToken(tok);
ParseStatement(tok, fn, returnLabel, breakLabel, continueLabel);
if (tok->token == TELSE) {
const int endifLabel = AllocLabel('I');
GetToken(tok);
EmitJump(endifLabel, "if: jump to endif");
EmitLabel(elseLabel);
ParseStatement(tok, fn, returnLabel, breakLabel, continueLabel);
EmitLabel(endifLabel);
}
else {
EmitLabel(elseLabel);
}
}
else {
Error("Expected ')' after <expression> in 'if'");
}
}
else {
Error("Expected '(' after 'if'");
}
}
/* ParseExpression --- parse a single expression */
void ParseExpression(struct Token *tok)
{
PrintSyntax("<expression>");
if (tok->token == TOPAREN) {
PrintSyntax("(");
GetToken(tok);
ParseExpression(tok);
if (tok->token == TCPAREN) {
GetToken(tok);
PrintSyntax(")");
}
else {
Error("Expected ')' after expression");
}
}
else if (tok->token == TINTLIT) {
LoadIntConstant(tok->iValue, 'D', tok->str);
GetToken(tok);
}
else if (tok->token == TID) {
struct Symbol tmp;
struct Symbol *stp = NULL;
tmp.storageClass = SCEXTERN;
strncpy(tmp.name, tok->str, sizeof (tmp.name));
tmp.type = T_INT;
tmp.pLevel = 0;
tmp.label = 0;
tmp.fpOffset = 0;
tmp.readOnly = false;
if ((stp = LookUpLocalSymbol(tok->str)) == NULL) {
stp = LookUpExternSymbol(tok->str);
if (stp == NULL) {
Error("Undeclared identifier: %s", tok->str);
}
}
GetToken(tok);
if ((tok->token == TINC) || (tok->token == TDEC)) {
if (stp->readOnly) {
Error("inc/dec 'const' object %s", stp->name);
}
else {
LoadScalar(stp);
if (tok->token == TINC) {
EmitIncScalar(stp, 1);
}
else if (tok->token == TDEC) {
EmitIncScalar(stp, -1);
}
}
GetToken(tok);
}
else if (tok->token == TOPAREN) {
int stackedBytes = 0;
GetToken(tok);
if (tok->token == TCPAREN) {
EmitCallFunction(tmp.name, "call function no actual parameters");
GetToken(tok);
}
else {
do {
ParseExpression(tok);
if (tok->token == TCOMMA) {
GetToken(tok);
}
// TODO: actual parameters other than 2 bytes long
Emit("pshs", "d", "<actual parameter>");
stackedBytes += 2;
} while (tok->token != TCPAREN);
EmitCallFunction(tmp.name, "call function with parameters");
GetToken(tok);
//Error("Expected ')' in function call");
}
EmitStackCleanup(stackedBytes);
}
else if (tok->token == TASSIGN) {
GetToken(tok);
ParseExpression(tok);
if (stp->readOnly) {
Error("Assignment to 'const' object %s", stp->name);
}
else {
StoreScalar(stp);
}
}
else {
LoadScalar(stp);
}
}
else if (tok->token == TSTRLIT) {
const int strLit = AllocLabel('S');
Strings[NextStr].label = strLit;
strncpy(Strings[NextStr].str, tok->str, 256);
memcpy(Strings[NextStr].sValue, tok->sValue, tok->sLength);
Strings[NextStr].sLength = tok->sLength;
NextStr++;
LoadLabelAddr(strLit, tok->str);
GetToken(tok);
}
else if (tok->token == TCOMMA) {
}
else if (tok->token == TCPAREN) {
}
else {
Emit("nop", "", "<expression>");
GetToken(tok);
}
PrintSyntax("\n");
}
/* ParseDo --- parse a 'do' statement */
void ParseDo(struct Token *tok, const struct Symbol *const fn, const int returnLabel)
{
const int blabel = AllocLabel('b');
const int clabel = AllocLabel('c');
const int dlabel = AllocLabel('d');
PrintSyntax("<do>\n");
EmitLabel(dlabel);
GetToken(tok);
ParseStatement(tok, fn, returnLabel, blabel, clabel);
if (tok->token != TWHILE) {
Error("Expected 'while' after 'do'");
}
else {
PrintSyntax("<while> ");
GetToken(tok);
if (tok->token == TOPAREN) {
EmitLabel(clabel);
GetToken(tok);
ParseExpression(tok);
EmitCompareIntConstant(0, "do-while: test");
EmitBranchNotEqual(dlabel, "do-while: branch");
if (tok->token == TCPAREN) {
GetToken(tok);
ParseSemi(tok, "after 'do'-'while'");
}
else {
Error("Expected ')' after 'do'-'while'");
}
}
else {
Error("Expected '(' after 'do'-'while'");
}
}
EmitLabel(blabel);
}
/* ParseBreak --- parse a 'break' statement and check that it's valid */
void ParseBreak(struct Token *tok, const int breakLabel)
{
PrintSyntax("<break>\n");
GetToken(tok);
if (breakLabel == NOLABEL) {
Error("'break' not inside a loop or 'switch'");
}
else {
EmitJump(breakLabel, "break");
}
ParseSemi(tok, "after 'break'");
}
/* ParseContinue --- parse a 'continue' statement and check that it's valid */
void ParseContinue(struct Token *tok, const int continueLabel)
{
PrintSyntax("<continue>\n");
GetToken(tok);
if (continueLabel == NOLABEL) {
Error("'continue' not inside a loop");
}
else {
EmitJump(continueLabel, "continue");
}
ParseSemi(tok, "after 'continue'");
}
/* ParseGoto --- parse and ignore a 'goto' statement */
void ParseGoto(struct Token *tok)
{
PrintSyntax("<goto>\n");
GetToken(tok);
if (tok->token == TID) {
GetToken(tok); /* Ignore target label */
ParseSemi(tok, "after 'goto'");
}
else {
Error("Expected label name after 'goto'");
}
}
/* ParseWhile --- parse a 'while' statement */
void ParseWhile(struct Token *tok, const struct Symbol *const fn, const int returnLabel)
{
const int blabel = AllocLabel('b');
const int clabel = AllocLabel('c');
PrintSyntax("<while> ");
GetToken(tok);
if (tok->token == TOPAREN) {
EmitLabel(clabel);
GetToken(tok);
ParseExpression(tok);
EmitCompareIntConstant(0, "while: test");
EmitBranchIfEqual(blabel, "while: exit");
if (tok->token == TCPAREN) {
GetToken(tok);
ParseStatement(tok, fn, returnLabel, blabel, clabel);
EmitJump(clabel, "while: loop");
}
else {
Error("Expected ')' after 'while'");
}
}
else {
Error("Expected '(' after 'while'");