Hi,
On Tue, 28 Aug 2007, Sam Ravnborg wrote:
> Googeling I did not find a good description of where __extension__ can
> be used so I fail to see where in the parse.y file I shal add the
> keyword. I think __extension__ may be used both as a part of an
> expression AND as part of a typedef (as in this case) but I wonder if
> this is where it is limited to be used.
The grammatic rules involving __extension__ are these (the lhs stems from
the standard directly):
external-declaration:
__extension__ external-declaration
struct-declaration:
__extension__ struct-declaration
nested-declaration:
__extension__ nested-declaration
unary-operator: one of
__extension__ __real__ __imag__
The first three allow to put __extension__ in front of any external or
local declaration (including decls inside blocks, in C99), ala:
{
x = 1+3;
__extension__ int y = 3;
x += y;
}
the last one defines __extension__ as an unary operator, which can be
applied to all cast-expressions (which in turn are just unary
expressions). E.g.:
x = 1 + __extension__ (2+3);
Note that the decls include the C99 nested-decls in for statements:
for (__extension__ long long i = 0; ...)
Note further that there's a small ambiguity in parsing when just looking
forward one token, namely between decl and expression, like in this
example:
{ __extension__ int i;
vs.
{ __extension__ i + 2;
Here you can't decide if __extension__ introduces an expression or a decl.
Probably doesn't matter for your parser. Hope this helps.
Ciao,
Michael.
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