Add example for using pool as a class member

[karczex]

I added example for this, as it's not obvious at the first glance how
to handle pool as class member, and how to access it's data.

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This change is 

[codecov]

Codecov Report

Merging #1032 (58a11eb) into master (eca8f5f) will decrease coverage by 0.19%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1032      +/-   ##
==========================================
- Coverage   94.25%   94.06%   -0.20%     
==========================================
  Files          48       48              
  Lines        4720     4750      +30     
==========================================
+ Hits         4449     4468      +19     
- Misses        271      282      +11     

Flag	Coverage Δ
tests_clang_debug_cpp17	93.52% <ø> (-0.17%)	⬇️
tests_gcc_debug	92.01% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
include/libpmemobj++/pool.hpp	88.17% <100.00%> (+2.27%)	⬆️
include/libpmemobj++/condition_variable.hpp	73.80% <0.00%> (-4.77%)	⬇️
include/libpmemobj++/transaction.hpp	79.83% <0.00%> (-2.74%)	⬇️
...libpmemobj++/detail/enumerable_thread_specific.hpp	98.91% <0.00%> (-1.09%)	⬇️
...ude/libpmemobj++/container/concurrent_hash_map.hpp	93.88% <0.00%> (-0.32%)	⬇️

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[igchor]

Reviewed 2 of 4 files at r1.
Reviewable status: 2 of 4 files reviewed, 1 unresolved discussion (waiting on @karczex)

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examples/pool/pool_as_class_member.cpp, line 26 at r1 (raw file):

	/* pool object */
	pmem::obj::pool<persistent_data> pop;
	/* Pointer to data. */

?

[lukaszstolarczuk]

Reviewed 3 of 4 files at r1.
Reviewable status: 3 of 4 files reviewed, 6 unresolved discussions (waiting on @karczex)

a discussion (no related file):
in the commit message:

1. Please drop "I added" ;) (and re-phrase I guess)
2. it's data -> its data

---

---

examples/pool/pool_as_class_member.cpp, line 40 at r1 (raw file):

			std::cerr << "Cannot open pool: " << e.what()
				  << std::endl
				  << "Trying to create new one " << std::endl;

a new one

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examples/pool/pool_as_class_member.cpp, line 44 at r1 (raw file):

							    PMEMOBJ_MIN_POOL);
		}
		/* Assign persistent poiner to root object. */

1. pointer (misspell)
2. to the root object

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examples/pool/pool_as_class_member.cpp, line 64 at r1 (raw file):

	increment()
	{
		auto root_obj = pop.root();

maybe don't duplicate code - use set(x+1)

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examples/pool/pool_as_class_member.cpp, line 72 at r1 (raw file):

	print()
	{
		auto root_obj = pop.root();

you don't need this line, just use it below

[KFilipek]

Reviewed 4 of 4 files at r1.
Reviewable status: all files reviewed, 9 unresolved discussions (waiting on @karczex)

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examples/pool/pool_as_class_member.cpp, line 28 at r1 (raw file):

	/* Pointer to data. */

	static constexpr const char *layout = "pool_layout";

const char* is not enough?

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examples/pool/pool_as_class_member.cpp, line 41 at r1 (raw file):

			pop = pool<persistent_data>::create("poolfile", layout,
							    PMEMOBJ_MIN_POOL);

if pop is still nullptr then try to create instead of doing work under risk in catch clause outside of try block

---

examples/pool/pool_as_class_member.cpp, line 46 at r1 (raw file):

		/* Assign persistent poiner to root object. */
	}

Foo() = delete;

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 72 at r1 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

you don't need this line, just use it below

Done.

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 64 at r1 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

maybe don't duplicate code - use set(x+1)

Done.

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 46 at r1 (raw file):

Previously, KFilipek (Krzysztof Filipek) wrote…

Foo() = delete;

Done.

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 41 at r1 (raw file):

Previously, KFilipek (Krzysztof Filipek) wrote…

			pop = pool<persistent_data>::create("poolfile", layout,
							    PMEMOBJ_MIN_POOL);

if pop is still nullptr then try to create instead of doing work under risk in catch clause outside of try block

Done.

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 40 at r1 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

a new one

Done.

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 28 at r1 (raw file):

Previously, KFilipek (Krzysztof Filipek) wrote…

const char* is not enough?

Done.

[karczex]

---

examples/pool/pool_as_class_member.cpp, line 26 at r1 (raw file):

Previously, igchor (Igor Chorążewicz) wrote…

?

Done.

[karczex]

a discussion (no related file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

in the commit message:

1. Please drop "I added" ;) (and re-phrase I guess)
2. it's data -> its data

Done.

---

[lukaszstolarczuk]

Reviewed 3 of 3 files at r2.
Reviewable status: all files reviewed, 5 unresolved discussions (waiting on @igchor, @karczex, and @KFilipek)

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include/libpmemobj++/pool.hpp, line 47 at r2 (raw file):

 * @snippet pool/pool.cpp pool_base_example
 *
 * The exmple of using pool with RAII idom:

idiom

[karczex]

Reviewable status: 3 of 4 files reviewed, 5 unresolved discussions (waiting on @igchor, @KFilipek, and @lukaszstolarczuk)

---

examples/pool/pool_as_class_member.cpp, line 44 at r1 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

1. pointer (misspell)
2. to the root object

Done.

---

include/libpmemobj++/pool.hpp, line 47 at r2 (raw file):

Previously, lukaszstolarczuk (Łukasz Stolarczuk) wrote…

idiom

Done.

[lukaszstolarczuk]

Reviewed 1 of 1 files at r3.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @igchor and @KFilipek)

[KFilipek]

Reviewed 1 of 3 files at r2, 1 of 1 files at r3.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @igchor)

[KFilipek]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @igchor)

[igchor]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @karczex)