This avoids a race condition in which the connection was
made but the version handshake is not completed yet. In that
case transactions won't be broadcasted to a peer yet, and
the nodes will wait forever for their mempools to sync.
`&vch[vch.size()]` and even `&vch[0]` on vectors can cause assertion
errors with VC in debug mode. This is the problem mentioned in #4239.
The deeper problem with this is that we rely on undefined behavior.
- Add `begin_ptr` and `end_ptr` functions that get the beginning and end
pointer of vector in a reliable way that copes with empty vectors and
doesn't reference outside the vector
(see https://stackoverflow.com/questions/1339470/how-to-get-the-address-of-the-stdvector-buffer-start-most-elegantly/1339767#1339767).
- Add a convenience constructor to CFlatData that wraps a vector.
I added `begin_ptr` and `end_ptr` as separate functions as I imagine
they will be useful in more places.
a0495bb Add <Hasher>::OUTPUT_SIZE (Pieter Wuille)
4791b99 crypto: create a separate lib for crypto functions (Cory Fields)
f2647cc crypto: explicitly check for byte read/write functions (Cory Fields)
5437248 build: move bitcoin-config.h to its own directory (Cory Fields)
3820e01 Extend and move all crypto tests to crypto_tests.cpp (Pieter Wuille)
7ecd973 Move {Read,Write}{LE,BE}{32,64} to common.h and use builtins if possible (Pieter Wuille)
a5bc9c0 Add built-in RIPEMD-160 implementation (Pieter Wuille)
13b5dfe Move crypto implementations to src/crypto/ (Pieter Wuille)
1cc344c Add built-in SHA-1 implementation. (Pieter Wuille)
85aab2a Switch miner.cpp to use sha2 instead of OpenSSL. (Pieter Wuille)
cf0c47b Remove getwork() RPC call (Pieter Wuille)
7b4737c Switch script.cpp and hash.cpp to use sha2.cpp instead of OpenSSL. (Pieter Wuille)
977cdad Add a built-in SHA256/SHA512 implementation. (Pieter Wuille)
6afa493 rpc: Add acceptors only when listening succeeded (Wladimir J. van der Laan)
33e5b42 rpc: Ignore and log errors during cancel (Wladimir J. van der Laan)
Cancelling the RPC acceptors can sometimes result in an error about
a bad file descriptor.
As this is the shutdown sequence we need to continue nevertheless,
ignore these errors, log a warning and proceed.
Fixes#4352.
Wladimir J. van der Laan