Fsa/report mmap on failure

[finnschiermer]

What, How & Why?

This PR

• Associates every memory mapping with the point in the source code, where it was created.
• On mmap failure, we log all mappings. If our respons on mmap failure is to throw, we now include a list of all mappings in the exception string
• The "page reclaimer" in the encryption layer has been removed.

The format of the dumped list is as follows:

Mappings at point of failure:
    0x7f4400000000 - 0x7f4400001000          1000    primary       --M
    0x7f4400001000 - 0x7f4404000000       3fff000    primary       FR-                          /home/finn/core/realm-core/build.release/testShared_MultipleSharersOfStreamingFormat.1.path.realm
    0x7f441426e000 - 0x7f441426f000          1000    primary       --M
    0x7f441426f000 - 0x7f441826e000       3fff000    primary       FR-                          /home/finn/core/realm-core/build.release/testShared_MultipleSharersOfStreamingFormat.1.path.realm
    0x7f44187ff000 - 0x7f4418800000          1000    block wr      --M
    0x7f4418800000 - 0x7f44188006c0           6c0    versions      F--            0 in File     /home/finn/core/realm-core/build.release/testShared_MultipleSharersOfStreamingFormat.1.path.realm.lock
    0x7f4418801000 - 0x7f44188016c0           6c0    meta          F--            0 in File     /home/finn/core/realm-core/build.release/testShared_MultipleSharersOfStreamingFormat.1.path.realm.lock
    0x7f4418802000 - 0x7f44188026c0           6c0    versions      F--            0 in File     /home/finn/core/realm-core/build.release/testShared_MultipleSharersOfStreamingFormat.1.path.realm.lock
    0x7f441883c000 - 0x7f441883c6c0           6c0    meta          F--            0 in File     /home/finn/core/realm-core/build.release/testShared_MultipleSharersOfStreamingFormat.1.path.realm.lock

[coveralls-official]

Pull Request Test Coverage Report for Build github_pull_request_284258

• 305 of 320 (95.31%) changed or added relevant lines in 11 files are covered.
• 34 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+0.3%) to 91.935%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/realm/db.cpp	5	6	83.33%
test/test_transactions.cpp	0	1	0.0%
src/realm/util/file.cpp	30	32	93.75%
src/realm/util/file_mapper.cpp	176	187	94.12%

Files with Coverage Reduction	New Missed Lines	%
src/realm/array_string.cpp	2	88.0%
src/realm/transaction.cpp	2	94.71%
src/realm/sync/noinst/server/server.cpp	3	75.86%
src/realm/alloc_slab.cpp	4	98.27%
src/realm/index_string.cpp	6	87.87%
src/realm/util/file_mapper.cpp	8	93.5%
src/realm/util/file.cpp	9	94.54%

Totals
Change from base Build 1829:	0.3%
Covered Lines:	232286
Relevant Lines:	252663

---

💛 - Coveralls

[jedelbo]

I would like to have a unit test for memory mapping where the logging functionality is exercised.

Review to be continued.