prep.c

Preprocessor

This is the built-in C preprocessor of the compiler. It is invoked by the scanner.

/*
 *	NMH's Simple C Compiler, 2011,2012
 *	Preprocessor
 */

#include "defs.h"
#include "data.h"
#include "decl.h"

void playmac(char *s) {
	if (Mp >= MAXNMAC) fatal("too many nested macros");
	Macc[Mp] = next();
	Macp[Mp++] = s;
}

static void defmac(void) {
	char	name[NAMELEN+1];
	char	buf[TEXTLEN+1], *p;
	int	k, y;

	Token = scanraw();
	if (Token != IDENT)
		error("identifier expected after '#define': %s", Text);
	copyname(name, Text);
	if ('\n' == Putback)
		buf[0] = 0;
	else
		fgets(buf, TEXTLEN-1, Infile);
	k = strlen(buf);
	if (k) buf[k-1] = 0;
	for (p = buf; isspace(*p); p++)
		;
	if ((y = findmac(name)) != 0) {
		if (strcmp(Mtext[y], buf))
			error("macro redefinition: %s", name);
	}
	else {
		addglob(name, 0, TMACRO, 0, 0, 0, globname(p), 0);
	}
	Line++;
}

static void undef(void) {
	char	name[NAMELEN+1];
	int	y;

	Token = scanraw();
	copyname(name, Text);
	if (IDENT != Token)
		error("identifier expected after '#undef': %s", Text);
	if ((y = findmac(name)) != 0)
		Names[y] = "#undef'd";
}

static void include(void) {
	char	file[TEXTLEN+1], path[TEXTLEN+1];
	int	c, k;
	FILE	*inc, *oinfile;
	char	*ofile;
	int	oc, oline;

	if ((c = skip()) == '<')
		c = '>';
	fgets(file, TEXTLEN-strlen(SCCDIR)-9, Infile);
	Line++;
	k = strlen(file);
	file[k-1] = 0;
	if (file[k-2] != c)
		error("missing delimiter in '#include'", NULL);
	file[k-2] = 0;
	if (c == '"')
		strcpy(path, file);
	else {
		strcpy(path, SCCDIR);
		strcat(path, "/include/");
		strcat(path, file);
	}
	if ((inc = fopen(path, "r")) == NULL)
		error("cannot open include file: %s", path);
	else {
		Inclev++;
		oc = next();
		oline = Line;
		ofile = File;
		oinfile = Infile;
		Line = 1;
		putback('\n');
		File = path;
		Infile = inc;
		Token = scan();
		while (XEOF != Token)
			top();
		Line = oline;
		File = ofile;
		Infile = oinfile;
		fclose(inc);
		putback(oc);
		Inclev--;
	}
}

static void ifdef(int expect) {
	char	name[NAMELEN+1];

	if (Isp >= MAXIFDEF)
		fatal("too many nested #ifdef's");
	Token = scanraw();
	copyname(name, Text);
	if (IDENT != Token)
		error("identifier expected in '#ifdef'", NULL);
	if (frozen(1))
		Ifdefstk[Isp++] = P_IFNDEF;
	else if ((findmac(name) != 0) == expect)
		Ifdefstk[Isp++] = P_IFDEF;
	else
		Ifdefstk[Isp++] = P_IFNDEF;
}

static void p_else(void) {
	if (!Isp)
		error("'#else' without matching '#ifdef'", NULL);
	else if (frozen(2))
		;
	else if (P_IFDEF == Ifdefstk[Isp-1])
		Ifdefstk[Isp-1] = P_ELSENOT;
	else if (P_IFNDEF == Ifdefstk[Isp-1])
		Ifdefstk[Isp-1] = P_ELSE;
	else
		error("'#else' without matching '#ifdef'", NULL);
		
}

static void endif(void) {
	if (!Isp)
		error("'#endif' without matching '#ifdef'", NULL);
	else
		Isp--;
}

static void junkln(void) {
	while (!feof(Infile) && fgetc(Infile) != '\n')
		;
	Line++;
}

int frozen(int depth) {
	return Isp >= depth &&
		(P_IFNDEF == Ifdefstk[Isp-depth] ||
		P_ELSENOT == Ifdefstk[Isp-depth]);
}

void preproc(void) {
	putback('#');
	Token = scanraw();
	if (	frozen(1) &&
		(P_DEFINE == Token || P_INCLUDE == Token || P_UNDEF == Token)
	) {
		junkln();
		return;
	}
	switch (Token) {
	case P_DEFINE:	defmac(); break;
	case P_UNDEF:	undef(); break;
	case P_INCLUDE:	include(); break;
	case P_IFDEF:	ifdef(1); break;
	case P_IFNDEF:	ifdef(0); break;
	case P_ELSE:	p_else(); break;
	case P_ENDIF:	endif(); break;
	default:	junkln(); break;
			break;
	}
}

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