std::initializer_list support is problematic and not needed

[TieJu]

The explicit support for std::initializer_list is not really needed and creates some problems that can cause bugs.

The compiler try's to match the best matching constructor and the std::initializer_list one will grab all uniform initialization variants with any length and the compiler is no longer able to select the expected constructor.
This causes a list of problems and bugs:

• any list that has not N elements (for vecN): undefined behavior ( if the list is shorter than N ) or assert fail.
• copy/cast: the assignment at the constructor will fail because of type mismatch for each member.

You only need a std::initializer_list constructors for containers if your data type supports a construction of a list of variable number of elements, like std::vector, for data types with fixed length you gain nothing because the compiler already try's to match the other constructors to that list.

I tested this problematic behavior on ms vc++ 2013 ( and nov ctp ).

[Groovounet]

Well in practice if I disable the initializer_list contructors and compile the core_type_mat4x4.cpp unit tests I get the following errors:

/Users/christophericcio/Documents/Repository/Github/glm/test/core/core_type_mat4x4.cpp:203:12:
No matching constructor for initialization of 'glm::mat4' (aka 'tmat4x4<float, highp>')
/Users/christophericcio/Documents/Repository/Github/glm/test/core/core_type_mat4x4.cpp:215:25: No matching constructor for initialization of 'std::vectorglm::mat4'

/Users/christophericcio/Documents/Repository/Github/glm/test/core/core_type_mat4x4.cpp:230:25: No matching constructor for initialization of 'std::vectorglm::mat4'

/Users/christophericcio/Documents/Repository/Github/glm/test/core/core_type_mat4x4.cpp:235:25: No matching constructor for initialization of 'std::vectorglm::mat4'

This was tested on Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn).

I also tested the behaviour of VC13 and it's very similar.

Thanks,
Christophe

[TieJu]

You need to remove the 'explicit'ness of many constructors that are needed to do the initialization of mat4 and vec4, then it will work.
Explicit is only needed for one parameter constructors to prohibit transformations from one type to an other, like from a single int to a vec or matrix, what is clearly not desired, for multi-param constructors this makes the constructors unusable for such desired transformations.

[Groovounet]

This issue is fixed in GLM 0.9.5 branch for next.

I removed the initializer_list constructors and removed some explicit constructors.

Thanks for contributing,
Christophe