Subject:
Re: some question about the directive GLOBAL in the source code.
From:
feqin fan ####@####.####
Date:
17 Aug 2012 06:24:42 -0000
Message-Id: <CAOfAq_oRiZxMM1mCGwn2G_1032JJqZatgGLCTrFUAdvZ7MQyag@mail.gmail.com>
My english writing is poor, Maybe it misled you, Sorry , It’s my fault.
I’m here discussing the assembler source code’s behavior, Not CPU’s
behavior.
the directive “global var” must be executed by assembler.
and in line 5,the function maybe_evaluate_concat() does not to query symbol
table, it just do some macro process, and must be return the string “var”.
Thanks for you letter..
:-)
2012/8/17 Tamas Rudnai ####@####.####
> The "global var" will never be "executed" as that is not an instruction but
> a directive. But that is not important right now.
>
> What is important that although I have never looked at the full source code
> and therefore not sure what are those functions and macros doing there, but
> following your logic in the comments, the "p will point to var" in line 5.
> Now if var is unknown at that stage, then maybe p will be NULL, right? So
> because of the condition at line 6, the compiler will never make it to the
> line 7... Just my cents.
>
> Tamas
>
>
>
> On 15 August 2012 19:50, feqin fan ####@####.#### wrote:
>
> > because the symbol_table stTop have nothing about symbol "var", the
> source
> > line "global var" is first line executed by assembler.
> >
> > all of this are my inferences.
> >
> > :-)
> >
> > THX..
> >
> > 2012/8/16 Holger Oehm ####@####.####
> >
> > > -----BEGIN PGP SIGNED MESSAGE-----
> > > Hash: SHA1
> > >
> > > 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???
> > > -----BEGIN PGP SIGNATURE-----
> > > Version: GnuPG v1.4.11 (GNU/Linux)
> > > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
> > >
> > > iEYEARECAAYFAlAr48sACgkQHdk+97UOUanAAgCfYSdqul+vqfA3ARzB38GScQGT
> > > 8lUAoIVHttJ6BOx1WLJCph25B4ak3+dN
> > > =N8FO
> > > -----END PGP SIGNATURE-----
> > >
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> > >
> >
>
>
>
> --
> int main() { char *a,*s,*q; printf(s="int main() { char *a,*s,*q;
> printf(s=%s%s%s, q=%s%s%s%s,s,q,q,a=%s%s%s%s,q,q,q,a,a,q); }",
> q="\"",s,q,q,a="\\",q,q,q,a,a,q); }
>
