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Refactor variable and enum declarations to be statements. #38

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Refactor variable and enum declarations to be statements. #38

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75affa2
Refactor variable and enum declarations to be statements.
avorobey Mar 22, 2018
07da7f3
Add support for initialization of locals: int i = [expr].
avorobey Mar 25, 2018
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182 changes: 85 additions & 97 deletions c4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -22,13 +22,14 @@ int *e, *le, // current position in emitted code
ival, // current token value
ty, // current expression type
loc, // local variable offset
ld, // local variable depth
line, // current line number
src, // print source and assembly flag
debug; // print executed instructions

// tokens and classes (operators last and in precedence order)
enum {
Num = 128, Fun, Sys, Glo, Loc, Id,
Num = 128, Fun, Sys, Glo, Par, Loc, Id,
Char, Else, Enum, If, Int, Return, Sizeof, While,
Assign, Cond, Lor, Lan, Or, Xor, And, Eq, Ne, Lt, Gt, Le, Ge, Shl, Shr, Add, Sub, Mul, Div, Mod, Inc, Dec, Brak
};
Expand Down Expand Up @@ -164,7 +165,7 @@ void expr(int lev)
}
else if (d[Class] == Num) { *++e = IMM; *++e = d[Val]; ty = INT; }
else {
if (d[Class] == Loc) { *++e = LEA; *++e = loc - d[Val]; }
if (d[Class] == Loc || d[Class] == Par) { *++e = LEA; *++e = loc - d[Val]; }
else if (d[Class] == Glo) { *++e = IMM; *++e = d[Val]; }
else { printf("%d: undefined variable\n", line); exit(-1); }
*++e = ((ty = d[Type]) == CHAR) ? LC : LI;
Expand Down Expand Up @@ -280,21 +281,95 @@ void expr(int lev)
}
}

void stmt()
void stmt(int ctx)
{
int bt, ty, i;
int *a, *b;

if (tk == If) {
if (tk == Enum) {
next();
if (tk != '{') next();
if (tk == '{') {
next();
i = 0;
while (tk != '}') {
if (tk != Id) { printf("%d: bad enum identifier %d\n", line, tk); exit(-1); }
next();
if (tk == Assign) {
next();
if (tk != Num) { printf("%d: bad enum initializer\n", line); exit(-1); }
i = ival;
next();
}
id[Class] = Num; id[Type] = INT; id[Val] = i++;
if (tk == ',') next();
}
next();
}
}
else if (tk == Int || tk == Char) {
bt = (tk == Int) ? INT : CHAR; // basetype
next();
while (tk != ';' && tk != '}' && tk != ',' && tk != ')') {
ty = bt;
while (tk == Mul) { next(); ty = ty + PTR; }
if (tk != Id) { printf("%d: bad declaration\n", line); exit(-1); }
if (id[Class] >= ctx) { printf("%d: duplicate definition\n", line); exit(-1); }
next();
if (tk == '(') { // function
if (ctx != Glo) { printf("%d: nested function\n", line); exit(-1); }
id[Class] = Fun;
id[Val] = (int)(e + 1);
id[Type] = ty;
next(); ld = 0;
while (tk != ')') {
stmt(Par);
if (tk == ',') next();
}
next();
if (tk != '{') { printf("%d: bad function definition\n", line); exit(-1); }
loc = ++ld; ++ld;
next();
*++e = ENT; a = ++e;
while (tk != '}') stmt(Loc);
*a = ld - loc - 1;
*++e = LEV;
id = sym; // unwind symbol table locals
while (id[Tk]) {
if (id[Class] == Loc || id[Class] == Par) {
id[Class] = id[HClass];
id[Type] = id[HType];
id[Val] = id[HVal];
}
id = id + Idsz;
}
}
else {
id[HClass] = id[Class]; id[Class] = ctx;
id[HType] = id[Type]; id[Type] = ty;
id[HVal] = id[Val];
if (ctx == Glo) { id[Val] = (int)data; data = data + sizeof(int); }
else { id[Val] = ld++; }
if (ctx == Loc && tk == Assign) { // initialization
*++e = LEA; *++e = loc - id[Val]; *++e = PSH;
next();
expr(Assign); *++e = (ty == CHAR) ? SC : SI;
}
}
if (ctx != Par && tk == ',') next();
}
}
else if (tk == If) {
next();
if (tk == '(') next(); else { printf("%d: open paren expected\n", line); exit(-1); }
expr(Assign);
if (tk == ')') next(); else { printf("%d: close paren expected\n", line); exit(-1); }
*++e = BZ; b = ++e;
stmt();
stmt(ctx);
if (tk == Else) {
*b = (int)(e + 3); *++e = JMP; b = ++e;
next();
stmt();
stmt(ctx);
}
*b = (int)(e + 1);
}
Expand All @@ -305,7 +380,7 @@ void stmt()
expr(Assign);
if (tk == ')') next(); else { printf("%d: close paren expected\n", line); exit(-1); }
*++e = BZ; b = ++e;
stmt();
stmt(ctx);
*++e = JMP; *++e = (int)a;
*b = (int)(e + 1);
}
Expand All @@ -317,7 +392,7 @@ void stmt()
}
else if (tk == '{') {
next();
while (tk != '}') stmt();
while (tk != '}') stmt(ctx);
next();
}
else if (tk == ';') {
Expand Down Expand Up @@ -364,98 +439,11 @@ int main(int argc, char **argv)
p[i] = 0;
close(fd);

// parse declarations
// parse the program
line = 1;
next();
while (tk) {
bt = INT; // basetype
if (tk == Int) next();
else if (tk == Char) { next(); bt = CHAR; }
else if (tk == Enum) {
next();
if (tk != '{') next();
if (tk == '{') {
next();
i = 0;
while (tk != '}') {
if (tk != Id) { printf("%d: bad enum identifier %d\n", line, tk); return -1; }
next();
if (tk == Assign) {
next();
if (tk != Num) { printf("%d: bad enum initializer\n", line); return -1; }
i = ival;
next();
}
id[Class] = Num; id[Type] = INT; id[Val] = i++;
if (tk == ',') next();
}
next();
}
}
while (tk != ';' && tk != '}') {
ty = bt;
while (tk == Mul) { next(); ty = ty + PTR; }
if (tk != Id) { printf("%d: bad global declaration\n", line); return -1; }
if (id[Class]) { printf("%d: duplicate global definition\n", line); return -1; }
next();
id[Type] = ty;
if (tk == '(') { // function
id[Class] = Fun;
id[Val] = (int)(e + 1);
next(); i = 0;
while (tk != ')') {
ty = INT;
if (tk == Int) next();
else if (tk == Char) { next(); ty = CHAR; }
while (tk == Mul) { next(); ty = ty + PTR; }
if (tk != Id) { printf("%d: bad parameter declaration\n", line); return -1; }
if (id[Class] == Loc) { printf("%d: duplicate parameter definition\n", line); return -1; }
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What is the impact after the removal of Line 412?

id[HClass] = id[Class]; id[Class] = Loc;
id[HType] = id[Type]; id[Type] = ty;
id[HVal] = id[Val]; id[Val] = i++;
next();
if (tk == ',') next();
}
next();
if (tk != '{') { printf("%d: bad function definition\n", line); return -1; }
loc = ++i;
next();
while (tk == Int || tk == Char) {
bt = (tk == Int) ? INT : CHAR;
next();
while (tk != ';') {
ty = bt;
while (tk == Mul) { next(); ty = ty + PTR; }
if (tk != Id) { printf("%d: bad local declaration\n", line); return -1; }
if (id[Class] == Loc) { printf("%d: duplicate local definition\n", line); return -1; }
id[HClass] = id[Class]; id[Class] = Loc;
id[HType] = id[Type]; id[Type] = ty;
id[HVal] = id[Val]; id[Val] = ++i;
next();
if (tk == ',') next();
}
next();
}
*++e = ENT; *++e = i - loc;
while (tk != '}') stmt();
*++e = LEV;
id = sym; // unwind symbol table locals
while (id[Tk]) {
if (id[Class] == Loc) {
id[Class] = id[HClass];
id[Type] = id[HType];
id[Val] = id[HVal];
}
id = id + Idsz;
}
}
else {
id[Class] = Glo;
id[Val] = (int)data;
data = data + sizeof(int);
}
if (tk == ',') next();
}
stmt(Glo);
next();
}

Expand Down