Hi,
I'm hoping a C++ language expert can help me with scoping rules for named
function parameters.
As background, I'd like to allow named function parameters in non-function
declarations (such as function-pointer-typed variables) to be referenced in
attribute expressions. Currently, attempting to do so results in "use of
undeclared identifier". However, I'm not even sure the standard allows me to
do this, let alone what assumptions any patch to clang might run afoul of.
Consider the declaration:
void (*pFn)(int x);
Reading the standard (specifically, I'm looking at C++11 draft N4527), I gather
that:
?1. pFn is not a "function declarator". I didn't see a clear definition of
this, but I assume function and variable are mutually exclusive descriptions of
a declarator, and that this would be a variable declarator.
2. According to [basic.scope.proto] (3.3.4), named parameters inside function
declarators which are not also definitions have function prototype scope, but
this only applies to function declarators. I do not find a scoping rule that
would apply to x in my pFn example, assuming point 1 is correct.
This seems like x has no applicable scoping rule and you shouldn't be able to
reference it. However, I note the following declaration is accepted as valid
C++11:
auto (*pSum)(int x, double y) -> decltype(x + y);
I'd appreciate any help understanding what portions of the standard apply to my
examples and how to interpret them, and whether the standard in fact allows me
to place an attribute on pFn which references x.
Thanks,
David Fontaine
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