gnupic: some question about the directive GLOBAL in the source code.
Subject:
Re: some question about the directive GLOBAL in the source code.
From:
Holger Oehm ####@####.####
Date:
15 Aug 2012 18:01:51 -0000
Message-Id: <502BE3D2.2070308@holger-oehm.de>
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On 14.08.2012 12:35, feqin fan wrote:
> Hello, everybody, I'm sorry to trouble you again.
> I have read most of the source code of gputils. I have a query about
> the implementation of the directive GLOBAL.
> for example, Have this code:
>
> global var
>
> udata
> var res 1
>
> the assembler deal with the first line "global var",
> the calling sequence is like this : yyparse() - do_or_append_insn(char *,
> struct pnode *) - do_insn(char *, struct pnode *) - do_global()
> the function do_global() source code :
>
> 1, if (state.mode == absolute) {
> 2, gperror(GPE_OBJECT_ONLY, NULL);
> 3, } else {
> 4, for (; parms; parms = TAIL(parms)) {
> 5, p = maybe_evaluate_concat(HEAD(parms)); //p will point to
> "var".
> 6, if (p) {
> 7, s = get_symbol(state.stTop, p); //s will be NULL
> 8, if (s == NULL) {
> 9, snprintf(buf,
> 10, sizeof(buf),
> 11 "Symbol not previously defined (%s).",
> 12, p);
> 13, gperror(GPE_NOSYM, buf);
>
>
>
> the line 4 must be first executed, in line 5 the p will point to "var". and
> in line 7, because the source code "global var" is the first line of the
> being assembled code.
> So. in the function do_global() line 7, the s will be NULL,
And why exactly should s be NULL after the assignment in line 7???
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