FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

> From: Thompson, Bill D (London) [mailto:ThompBil AT exchange.uk.ml.com]
> Sent: March 19, 2003 12:39 PM
> 
> " the expressions in the initializer for an auto or register 
> object or array
> must likewise be constant expressions if the initializer is a 
> brace enclosed list"
> 
> So I guess if clause_buffer is automatic, its address is not 
> regarded as a constant expression....

Hmm.  Am I then to understand that this is OK:

        char buf[8], *s = buf;

but not

        char buf[8], *s[] = {buf, buf};

because buf is not a constant expression and lies within a brace-enclosed
list?  I guess so.  I don't think the fact that the pointer is part of a
structure restricts its initialization rules.  

Looking at the definition of "constant expression" in the appendix, I can
see that the address of an automatic isn't known at compile time; of course
it's an offset of the value of the frame pointer.  

I cannot get gcc to generate even a warning for this.  

--jkl

> > From:       Lowden, James K [SMTP:LowdenJK AT bernstein.com]
> > Sent:       19 March 2003 16:46
> > To: 'FreeTDS Development Group'
> > Subject:    RE: [freetds] A new patch - various fixes
> > 
> > > From: Thompson, Bill D (London) 
> [mailto:ThompBil AT exchange.uk.ml.com]
> > > Sent: March 19, 2003 9:42 AM
> > > 
> > > Also changed initialisation of
> > > a structure in bcp.c - my compiler (Sun workshop cc 4.2) 
> objected...
> > 
> > Lemme get this straight.  Your compiler complained about:
> > 
> > TDS_PBCB colclause = { clause_buffer, sizeof(clause_buffer) };
> > 
> > even though both values are known at compile time (never 
> mind that it's an
> > ANSI standard construction)?  I find this hard to believe, 
> not because I
> > don't trust you, but because I've been initializing 
> structures that way
> > since before Bill Gates dropped out of Harvard.  It's explained and
> > illustrated in section 6.3 of "The C Programming Language", 
> copyright
> > 1988.
> > 
> > 
> > Does this work:
> > 
> > enum {CLAUSE_BUFFER_SIZE = 4096};
> > char clause_buffer[CLAUSE_BUFFER_SIZE] = {0};
> > TDS_PBCB colclause = { clause_buffer, CLAUSE_BUFFER_SIZE };
> > 
> > Does this:
> > 
> > #define CLAUSE_BUFFER_SIZE 4096
> > char clause_buffer[CLAUSE_BUFFER_SIZE] = {0};
> > TDS_PBCB colclause = { clause_buffer, CLAUSE_BUFFER_SIZE };
> > 
> > Section 2.4 of the same book, wherein initialization of variables is
> > described, says initialization of automatic variables may 
> be done with
> > "any
> > expression".  I think someone should mention this to Sun?  
> I could send
> > them
> > a copy. 
> > 
> > --jkl
> > 
> > 
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