Uniform sequence at start of source files
- copyright claim
- license
- file comment
- header guard
- lumiera includes
- library / system includes
Lumiera uses Brittish spelling. Add an according note to the styleguide.
This is a somewhat intricate problem. As long as we linked with --no-as-needed,
these problems could not manifest themselves, since all dependencies are spotted
correctly by SCons and thus added as direct children of the executable.
But when we switch to --as-needed linking, the linker will omit some of
the dependencies given from the build system, when the code to be linked
doesn't call directly into these dependencies. But of course dynamic modules
may depend on each other, and indeed, the Lumiera libs do so. Thus
the linker may omit the dependency to liblumierasupport, and just add
a dependency to, say liblumierabackend. But the backend in turn
depends on the support library.
Now the problem is, that when resolving several steps deep into such
a dependency chain, our special relative path resolution scheme fails.
The fix is to give each lumiera module itself another relative path
resolution spec, which overrides at that point the root spec given
for the executable. Thus, we define
- for the executable: "search at $ORIGIN/modules"
- for the modules: "search at $ORIGIN/../modules"
This accounts for the fact, that a module, which is the Origin
for a transitive resolution step, already sits in a subdirectory
below the executable; thus step one level up and devle down into
the hard wired modules directory. Alternatively, we could also
use just "search at $ORIGIN" (i.e. in the same directory).
But assuming that in future we'll roll several core plugins,
which also count as "Lumiera modules", the scheme defined here
is more flexible, since it allows to place those core plugins
into sibling directories.
here we're iterating hash table based collections, consequently
the order of items retrieved *is* implementation dependent and indeed
differs on different platforms and compilers.
In Clang, static object fields are initialised from top to bottom,
but before any other variables in anoymous namespaces. To the contrary,
GCC evaluates *any* initialisation expression in the translation
unit together from top to bottom. Thus, in the clang generated
code, in two cases the static initialisation could use a not yet
constructed local lib::_Fmt formatter object.
as always, it turned out that the alledged "compiler bug"
rather was my own sloppyness: I forgot properly to undo a change
I made while fighting with compilation problems: the wrapper in
the factory didn't use std::forward, resulting in a plain flat
slicing copy. This, rightfully, triggered the assertion in the
session query resolver (since a sliced Goal can not be dynamic cast
to a specific Query subclass).
the alledged compiler error turned out to be
just plain flat lack of attention on my side.
I forgot to revert an previous experimental change:
The "wrapper" in the factory takes the argument by-value
(I forgot to add he && back in, which I removed while
fighting with other compilation problems)
TODO: the toolfactory needs a redesign anyway,
this was just placeholder code added in a very early
state of the Lumiera project. We have way better memory
managing facilities at hand now
the use of a custom finisihing functor, which is applied
to any generated product. This can be used for registration,
memory management or similar framework aspects
Implement the first simple usage scenario for the
unified MultiFact template, using variadic templates.
NOTE:
- the obvious solution based on std::forward
triggers strange behaviour in GCC-4.7
- the inline lambda in the test case traps the
CLang-3.0 parster with a segfault. Horay!
...but the whole design looks still overengineered. See #388
- should get rid of the explicit specialisation
- always use a function signature and thus have arguments?
- why inheriting from the wrapper?
still puzzled why this instantiation of MultiFact fails to compile with GCC 4.8
so I'm bound to understand why the types involved
need indeed to be are structured the way they are right now.
previous versions used to resolve this ambiguity in favour of a ctor call,
but now the compiler treats such constructs as function definition;
this is reasonable, since C++11 introduced the notion of a "generalised
initialisation", which is always written as a (possibly empty) list
in braces.
In these specific cases here, we just omit the empty parens
Since we have now a generic bridge to supply std::hash functions based on
an exisiting boost::hash function, we removed the explicit std::hash
specialisation for "Placement-ID".
This caused the PlacementIndex implementation to fail at compilation
with a quite obscure error, which in fact seems to be caused by the
absence of any specific specialisation. The symptom is that a iterator
range could not be assigned to the predefined iterator type of
std::unordered_multimap, due to a mismatch in the embedded traits type
__umap_traits<__cache_default<_Key, _Hash>::value>>
While I didn't track down that problem entirely, to verify my hypothesis,
the problem can be avoided by using the default -- which is now to
pick up an existing boost::hash function for this type and use this
to generate the std::hash function.
right now we have to defeat an unfortunate static assertion in
the standard library, which is expected to go away in the future.
We use a hack to hijack the problematic definition with the preprocessor,
which requires our header to be first.
NOTE: this header contains a potentially dangerous, temporary workaround
to defeat the static assertion in the default implementation of std::hash,
as shipped with GCC 4.7.x
This assertion turns out to be detrimental all kinds of metaprogramming
based solutions, since it defeats SFINAE. It is expected to be removed
in GCC 4.8
the rules are:
- our own headers go before any library headers
- all headers need to be spelled relative to include root
- ensure that gtk is always included via gui/gtk-base.hpp
this completes the exploration; we should now be able to use
any type with boost hash support in the std unordered containers
without much ado.
I wasn't able to come up with a completely modular solution, since
the std::hash template has only one template parameter, which
defeats using enable_if. But since we're controling the default
implementation after the Hijacking anyway, we can as well go
ahead directly to forward to an existing boost::hash function
this turns out to be quite tough, since boost::hash
just requires a free function 'hash_value' to be
"somehow" present, which might be just through ADL.
My solution is to inject an fallback declaration of such a function,
but only in the namespace where the trait template is defined.
Hopefully this never interferes with real hash functions defined
for use by boost::hash
start a systematic research about the coexistence of
std::hash and boost::hash. The goal is to build an
automatic bridge function -- but this is hampered by
the unfortunate standard implementation of std::hash
Since meanwhile even the GCC people seem to have realized
this wasn't a good idea, I am geared towards using a hack
to work around this problem, which can be expected to go
away with GCC 4.8.x
A possible idea how to construct such a workaround is
http://stackoverflow.com/questions/12753997/check-if-type-is-hashable
I start this investigation by defining two custom types,
each with his own extension point for hashing. The goal
would then be to use both in a standard hashtable container.
note down some results found out during the C++11 transition.
There is now a clear distinction between automatic type conversion
and the ability to construct a new instance
