os/include: resolve build warnings

[gSahitya-samsung]

Issue: Getting below build warnings

include/signal.h:590:83: WARNING: 'int sigaction(int, const sigaction*, sigaction*)' hides constructor for 'struct sigaction' [-Wshadow]

  590 | int sigaction(int sig, FAR const struct sigaction *act, FAR struct sigaction *oact);

include/stdlib.h:603:30: WARNING: 'mallinfo mallinfo()' hides constructor for 'struct mallinfo' [-Wshadow]

  603 | struct mallinfo mallinfo(void);

Cause: the struct sigaction and function sigaction is declared with same
name. During compilation they were part of same namespace that's
causing shadowing of struct with function declaration. Same is true for
mallinfo

Resolution: Disable shadow warning during function declaration and
enable it after declaration.

Note: GCC>=7 doesn't throw this error with -Wshadow flag. This
temporary changes is only needed to support build with old version of
GCC.

[ritesh55555]

build warnings resolved

[CookieDoughMixer]

This looks like a work around. Is it possible that these errors are occuring because we include c headers in cpp files? Will it be possible to resolve them by adding extern C at appropriate places?

[gSahitya-samsung]

This looks like a work around. Is it possible that these errors are occuring because we include c headers in cpp files? Will it be possible to resolve them by adding extern C at appropriate places?

Yes, its work around

The proper fix can be as follow:

1. Either change struct or function name
2. Move functions declaration into separate header file

But in our case, none of above will work.

Can we change -Wshadow to -Wshadow=compatible-local? It will also resolve the warnings message.

Reference - https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

[r-prabu]

This looks like a work around. Is it possible that these errors are occuring because we include c headers in cpp files? Will it be possible to resolve them by adding extern C at appropriate places?

@abhishek-samsung i think it is not because of cpp files. Also this is applied only for the few required lines which should not create a problem.

[kishore-sn]

Can we change -Wshadow to -Wshadow=compatible-local? It will also resolve the warnings message.

I think this might be a better option. Please try it out.