error: memunit_step was not declared in this scope

[mloskot]

trafficstars

(follow-up to https://github.com/boostorg/gil/pull/173#discussion_r239542235)

Actual behavior

Compile tests and examples with with -DBOOST_GIL_USE_CONCEPT_CHECK=1. For example, add the define to the GIL's top-level Jamfile:

project boost-gil
    :
    requirements
        <define>BOOST_GIL_USE_CONCEPT_CHECK
...

Run b2 -d 2 to confirm the define is included in the compiler command line:

Observer numerous compiler errors:

boost/gil/concepts/pixel_iterator.hpp:87:41: error: ‘memunit_step’ was not declared in this scope
boost/gil/concepts/pixel_iterator.hpp:90:30: error: ‘memunit_advanced’ was not declared in this scope
...

None of the memunit_* functions have ever been (forward) declared in any way, for example:

https://github.com/boostorg/gil/blob/boost-1.35.0/include/boost/gil/gil_concept.hpp https://github.com/boostorg/gil/blob/boost-1.60.0/include/boost/gil/gil_concept.hpp https://github.com/boostorg/gil/blob/boost-1.65.0/include/boost/gil/gil_concept.hpp

Expected behavior

No compilation error.

Environment

All relevant information like:

• Boost version (see <boost/version.hpp>): from 1.35 until 1.69
• Compiler version: GCC 5.5.0 but any C++11 compiler should fail

[mloskot]

This needs to be checked after #230 has been merged