Alternative approach to compile-time function substitutions for UT

[jphickey]

Is your feature request related to a problem? Please describe.
Currently, the OSAL coverage test overrides C library calls using a combination of a single "override" header file that correlates with the C library header file of the same name. This file declares stub versions of the same functions but with an OCS_ prefix.

This is combined with a "stub-map-to-real.h" header that uses #define statements to divert the original calls to the substitute (OCS) version at compile time.

The C library calls need to be stubbed out in this manner, because they cannot be done at link time (as the UT still needs to link with the real C library, unlike higher-level libraries).

Describe the solution you'd like
Put the #define statements in the substitute header itself, rather than in a local map file, and move the OCS_ prototypes and declarations to a new, separate header file.

Describe alternatives you've considered
The existing method of using a separate map file to provide the substitutions, but this complicates the build of the source units under test as this file must be explicitly included somehow.

Additional context
The change alleviates the need to inject the stup-map-to-real.h file as part of the compilation of the source unit under test, as it gets the overrides implicitly though the include path instead, so it simplifies the build for UT that needs this feature.

The trade-off is that it requires a pair of override headers for each real header being overridden, i.e. one for the OCS_ replacements and one for the actual #define statements to do the mapping. So for the OSAL coverage test, which override headers for about 80 different system headers, this adds quite a few files.

Requester Info
Joseph Hickey, Vantage Systems, Inc.

[skliper]

Is this ready to be a pull request?