samples(storagecontrol): add storagecontrol folder samples

[ddelgrosso1]

This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.22%. Comparing base (54274c0) to head (bdce3e2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #14332   +/-   ##
=======================================
  Coverage   93.22%   93.22%           
=======================================
  Files        2181     2181           
  Lines      191173   191173           
=======================================
+ Hits       178213   178222    +9     
+ Misses      12960    12951    -9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[coryan]

Calling std::move(client) here invalidates the client and causes the crash.

[coryan]

Hmm... Normally clang-tidy should give you a warning about that. I wonder why it didn't... Ah, because generated libraries do not get a clang-tidy build:

google-cloud-cpp/ci/lib/shard.sh

Lines 89 to 90 in 54274c0

	# If we decided to compile all libraries with clang-tidy we would need
	# to enable shards such as:

After we merge this PR, we should discuss with @scotthart and @dbolduc if they want to enable clang-tidy for any generated libraries with manual examples.

[ddelgrosso1]

Removed. But out of curiosity why does this crash?

[coryan]

You are using the move-constructor: note that std::move() by itself just says "please use the move constructor if available". There is a move constructor available: the compiler generated one, which performance member-by-member move construction. Oh, and because your lambda (now a function) consumes the client parameter by-value the constructor is called.

Move constructors (as the name implies) move or steal the contents of a the source object into the destination object ¹. That leaves the source object in an undetermined state ². Calling member functions that have pre-conditions may result in UB (undefined behavior). In this case the contents are a std::shared_ptr<>, the shared pointer move constructor leaves the source with a nullptr and dereferencing a nullptr causes a crash.

Footnotes

1. Well, move constructors can do whatever they want. They can behave like copy constructors. But by convention they move / steal the contents. ↩

2. Again, technically move constructors are required to leave the source object in a "consistent but undetermined state". It could be that the source object is left in a state where it is usable, but in general one should assume move constructors leave you with an object where only functions without preconditions (e.g. assigning to the object) work. ↩

[coryan]

A few nits left for you to consider. Otherwise it looks good.