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fix questionable construct

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this was spotted by a new GCC warning -Wunused-function
and I must admit, GCC is right here: an externally not visible
function in an anonymous namespace is not what I'd expect to be
picked up by ADL. It is rather weird that the metaprogramming
trait worked at all.

Note that the function is intentionally declared only, never defined.
We want a linker error in case boost::hash ever attempts to
use this 'deliberately ill-definded' catch-all.
This commit is contained in:
Fischlurch 2015-08-15 17:03:13 +02:00
parent a4e985b4ac
commit 32f1773288
1 changed files with 6 additions and 8 deletions
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14
src/lib/hash-standard.hpp
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@ -38,7 +38,7 @@
** to use this boost-style custom hash function if applicable. To allow for such an automatic bridge,
** we have to work around aforementioned problem with the static assertion. Recent discussion threads
** indicate that the GCC and Clang developers are aware of those likely unintended side effects of a
** well mentioned hint for people to implement their own hash functions. AFAIK, the standard lib shipping
** well meant hint for people to implement their own hash functions. AFAIK, the standard lib shipping
** with some GCC 4.8.x doesn't contain the assertion anymore; and there are plans to adopt the boost style
** extension mechanism and provide such a bridge in the standard library at some point in the future.
**
@ -78,13 +78,11 @@
namespace lib {
namespace meta {
namespace {
struct NoUsableHashDefinition { size_t more_than_one[2]; };
typedef size_t HasUsableHashDefinition;
NoUsableHashDefinition hash_value(...);
}
struct NoUsableHashDefinition { size_t more_than_one[2]; };
typedef size_t HasUsableHashDefinition;
NoUsableHashDefinition hash_value(...); ///< declared for metaprogramming only, never defined
/**
* trait template to detect if some custom type TY