object.c

早期freebsd实现

 * Try to find the symbol that is referred to by the given name.  Since it's
 * an external, we need to follow a level or two of indirection.
 */

private Symbol findsym (n, var_isextref)
Name n;
boolean *var_isextref;
{
    register Symbol r, s;

    *var_isextref = false;
    find(s, n) where
	(
	    s->level == program->level and (
		s->class == EXTREF or s->class == VAR or
		s->class == PROC or s->class == FUNC
	    )
	) or (
	    s->block == program and s->class == MODULE
	)
    endfind(s);
    if (s == nil) {
	r = nil;
    } else if (s->class == EXTREF) {
	*var_isextref = true;
	r = s->symvalue.extref;
	delete(s);

	/*
	 * Now check for another level of indirection that could come from
	 * a forward reference in procedure nesting information.  In this case
	 * the symbol has already been deleted.
	 */
	if (r != nil and r->class == EXTREF) {
	    r = r->symvalue.extref;
	}
/*
    } else if (s->class == MODULE) {
	s->class = FUNC;
	s->level = program->level;
	r = s;
 */
    } else {
	r = s;
    }
    return r;
}

/*
 * Create a symbol for a text symbol with no source information.
 * We treat it as an assembly language function.
 */

private Symbol deffunc (n)
Name n;
{
    Symbol f;

    f = insert(n);
    f->language = findlanguage(".s");
    f->class = FUNC;
    f->type = t_int;
    f->block = curblock;
    f->level = program->level;
    f->symvalue.funcv.src = false;
    f->symvalue.funcv.inlne = false;
    if (f->chain != nil) {
	panic("chain not nil in deffunc");
    }
    return f;
}

/*
 * Create a symbol for a data or bss symbol with no source information.
 * We treat it as an assembly language variable.
 */

private Symbol defvar (n)
Name n;
{
    Symbol v;

    v = insert(n);
    v->language = findlanguage(".s");
    v->storage = EXT;
    v->class = VAR;
    v->type = t_int;
    v->level = program->level;
    v->block = curblock;
    return v;
}

/*
 * Update a symbol entry with a text address.
 */

private updateTextSym (s, name, addr)
Symbol s;
char *name;
Address addr;
{
    if (s->class == VAR) {
	s->symvalue.offset = addr;
    } else {
	s->symvalue.funcv.beginaddr = addr;
	if (name[0] == '_') {
	    newfunc(s, codeloc(s));
	    findbeginning(s);
	}
    }
}

/*
 * Avoid seeing Pascal labels as text symbols.
 */

private boolean PascalLabel (n)
Name n;
{
    boolean b;
    register char *p;

    b = false;
    if (curlang == findlanguage(".p")) {
	p = ident(n);
	while (*p != '\0') {
	    if (*p == '_' and *(p+1) == '$') {
		b = true;
		break;
	    }
	    ++p;
	}
    }
    return b;
}

/*
 * Check to see if a global _name is already in the symbol table,
 * if not then insert it.
 */

private check_global (name, np)
String name;
register struct nlist *np;
{
    register Name n;
    register Symbol t, u;
    char buf[4096];
    boolean isextref;
    integer count;

    if (not streq(name, "_end")) {
	if (name[0] == '_') {
	    n = identname(&name[1], true);
	} else {
	    n = identname(name, true);
	    if (lookup(n) != nil) {
		sprintf(buf, "$%s", name);
		n = identname(buf, false);
	    }
	}
	if ((np->n_type&N_TYPE) == N_TEXT) {
	    count = 0;
	    t = findsym(n, &isextref);
	    while (isextref) {
		++count;
		updateTextSym(t, name, np->n_value);
		t = findsym(n, &isextref);
	    }
	    if (count == 0) {
		if (t == nil) {
		    if (not PascalLabel(n)) {
			t = deffunc(n);
			updateTextSym(t, name, np->n_value);
			if (tracesyms) {
			    printdecl(t);
			}
		    }
		} else {
		    if (t->class == MODULE) {
			u = t;
			t = deffunc(n);
			t->block = u;
			if (tracesyms) {
			    printdecl(t);
			}
		    }
		    updateTextSym(t, name, np->n_value);
		}
	    }
	} else if ((np->n_type&N_TYPE) == N_BSS or (np->n_type&N_TYPE) == N_DATA) {
	    find(t, n) where
		t->class == COMMON
	    endfind(t);
	    if (t != nil) {
		u = (Symbol) t->symvalue.common.offset;
		while (u != nil) {
		    u->symvalue.offset = u->symvalue.common.offset+np->n_value;
		    u = u->symvalue.common.chain;
		}
            } else {
		check_var(np, n);
	    }
        } else {
	    check_var(np, n);
	}
    }
}

/*
 * Check to see if a namelist entry refers to a variable.
 * If not, create a variable for the entry.  In any case,
 * set the offset of the variable according to the value field
 * in the entry.
 *
 * If the external name has been referred to by several other symbols,
 * we must update each of them.
 */

private check_var (np, n)
struct nlist *np;
register Name n;
{
    register Symbol t, u, next;
    Symbol conflict;

    t = lookup(n);
    if (t == nil) {
	t = defvar(n);
	t->symvalue.offset = np->n_value;
	if (tracesyms) {
	    printdecl(t);
	}
    } else {
	conflict = nil;
	do {
	    next = t->next_sym;
	    if (t->name == n) {
		if (t->class == MODULE and t->block == program) {
		    conflict = t;
		} else if (t->class == EXTREF and t->level == program->level) {
		    u = t->symvalue.extref;
		    while (u != nil and u->class == EXTREF) {
			u = u->symvalue.extref;
		    }
		    u->symvalue.offset = np->n_value;
		    delete(t);
		} else if (t->level == program->level and
		    (t->class == VAR or t->class == PROC or t->class == FUNC)
		) {
		    conflict = nil;
		    t->symvalue.offset = np->n_value;
		}
	    }
	    t = next;
	} while (t != nil);
	if (conflict != nil) {
	    u = defvar(n);
	    u->block = conflict;
	    u->symvalue.offset = np->n_value;
	}
    }
}

/*
 * Check to see if a local _name is known in the current scope.
 * If not then enter it.
 */

private check_local (name, np)
String name;
register struct nlist *np;
{
    register Name n;
    register Symbol t, cur;

    n = identname(name, true);
    cur = ((np->n_type&N_TYPE) == N_TEXT) ? curmodule : curblock;
    find(t, n) where t->block == cur endfind(t);
    if (t == nil) {
	t = insert(n);
	t->language = findlanguage(".s");
	t->type = t_int;
	t->block = cur;
	t->storage = EXT;
	t->level = cur->level;
	if ((np->n_type&N_TYPE) == N_TEXT) {
	    t->class = FUNC;
	    t->symvalue.funcv.src = false;
	    t->symvalue.funcv.inlne = false;
	    t->symvalue.funcv.beginaddr = np->n_value;
	    newfunc(t, codeloc(t));
	    findbeginning(t);
	} else {
	    t->class = VAR;
	    t->symvalue.offset = np->n_value;
	}
    }
}

/*
 * Check to see if a symbol corresponds to a object file name.
 * For some reason these are listed as in the text segment.
 */

private check_filename (name)
String name;
{
    register String mname;
    register integer i;
    Name n;
    Symbol s;

    mname = strdup(name);
    i = strlen(mname) - 2;
    if (i >= 0 and mname[i] == '.' and mname[i+1] == 'o') {
	mname[i] = '\0';
	--i;
	while (mname[i] != '/' and i >= 0) {
	    --i;
	}
	n = identname(&mname[i+1], true);
	find(s, n) where s->block == program and s->class == MODULE endfind(s);
	if (s == nil) {
	    s = insert(n);
	    s->language = findlanguage(".s");
	    s->class = MODULE;
	    s->symvalue.funcv.beginaddr = 0;
	    findbeginning(s);
	}
	if (curblock->class != PROG) {
	    exitblock();
	    if (curblock->class != PROG) {
		exitblock();
	    }
	}
	enterblock(s);
	curmodule = s;
    }
}

/*
 * Check to see if a symbol is about to be defined within an unnamed block.
 * If this happens, we create a procedure for the unnamed block, make it
 * "inline" so that tracebacks don't associate an activation record with it,
 * and enter it into the function table so that it will be detected
 * by "whatblock".
 */

public chkUnnamedBlock ()
{
    register Symbol s;
    static int bnum = 0;
    char buf[100];
    Address startaddr;

    if (nesting > 0 and addrstk[nesting] != NOADDR) {
	startaddr = (linep - 1)->addr;
	++bnum;
	sprintf(buf, "$b%d", bnum);
	s = insert(identname(buf, false));
	s->language = curlang;
	s->class = PROC;
	s->symvalue.funcv.src = false;
	s->symvalue.funcv.inlne = true;
	s->symvalue.funcv.beginaddr = startaddr;
	enterblock(s);
	newfunc(s, startaddr);
	addrstk[nesting] = NOADDR;
    }
}

/*
 * Compilation unit.  C associates scope with filenames
 * so we treat them as "modules".  The filename without
 * the suffix is used for the module name.
 *
 * Because there is no explicit "end-of-block" mark in
 * the object file, we must exit blocks for the current
 * procedure and module.
 */

private enterSourceModule (n, addr)
Name n;
Address addr;
{
    register Symbol s;
    Name nn;
    String mname, suffix;

    mname = strdup(ident(n));
    if (rindex(mname, '/') != nil) {
	mname = rindex(mname, '/') + 1;
    }
    suffix = rindex(mname, '.');
    if (suffix > mname && *(suffix-1) == '.') {
	/* special hack for C++ */
	--suffix;
    }
    curlang = findlanguage(suffix);
    if (curlang == findlanguage(".f")) {
	strip_ = true;
    } 
    if (suffix != nil) {
	*suffix = '\0';
    }
    if (not (*language_op(curlang, L_HASMODULES))()) {
	if (curblock->class != PROG) {
	    exitblock();
	    if (curblock->class != PROG) {
		exitblock();
	    }
	}
	nn = identname(mname, true);
	if (curmodule == nil or curmodule->name != nn) {
	    s = insert(nn);
	    s->class = MODULE;
	    s->symvalue.funcv.beginaddr = 0;
	    findbeginning(s);
	} else {
	    s = curmodule;
	}
	s->language = curlang;
	enterblock(s);
	curmodule = s;
    }
    if (program->language == nil) {
	program->language = curlang;
    }
    warned = false;
    enterfile(ident(n), addr);
    initTypeTable();
}

/*
 * Allocate file and line tables and initialize indices.
 */

private allocmaps (nf, nl)
integer nf, nl;
{
    if (filetab != nil) {
	dispose(filetab);
    }
    if (linetab != nil) {
	dispose(linetab);
    }
    filetab = newarr(Filetab, nf);
    linetab = newarr(Linetab, nl);
    filep = filetab;
    linep = linetab;
}

/*
 * Add a file to the file table.
 *
 * If the new address is the same as the previous file address
 * this routine used to not enter the file, but this caused some
 * problems so it has been removed.  It's not clear that this in
 * turn may not also cause a problem.
 */

private enterfile (filename, addr)
String filename;
Address addr;
{
    filep->addr = addr;
    filep->filename = filename;
    filep->lineindex = linep - linetab;
    ++filep;
}

/*
 * Since we only estimated the number of lines (and it was a poor
 * estimation) and since we need to know the exact number of lines
 * to do a binary search, we set it when we're done.
 */

private setnlines ()
{
    nlhdr.nlines = linep - linetab;
}

/*
 * Similarly for nfiles ...
 */

private setnfiles ()
{
    nlhdr.nfiles = filep - filetab;
    setsource(filetab[0].filename);
}