Avoid static analyzer warnings regarding uninitialized arguments

[practicalswift]

Avoid static analyzer warnings regarding "Function call argument is a pointer to uninitialized value" in cases where we are intentionally using such arguments.

This is achieved by using f(b.begin(), b.end()) (std::array<char, N>) instead of f(b, b + N) (char b[N]).

Rationale:

• Reduce false positives by guiding static analyzers regarding our intentions.

Before this commit:

$ clang-tidy-3.5 -checks=* src/bench/base58.cpp
bench/base58.cpp:23:9: warning: Function call argument is a pointer to uninitialized value [clang-analyzer-core.CallAndMessage]
        EncodeBase58(b, b + 32);
        ^
$ clang-tidy-3.5 -checks=* src/bench/verify_script.cpp
bench/verify_script.cpp:59:5: warning: Function call argument is a pointer to uninitialized value [clang-analyzer-core.CallAndMessage]
    key.Set(vchKey, vchKey + 32, false);
    ^
$

After this commit:

$ clang-tidy-3.5 -checks=* src/bench/base58.cpp
$ clang-tidy-3.5 -checks=* src/bench/verify_script.cpp
$

[sipa]

While you're at it, make these static const ?

[practicalswift]

@sipa Good point! Fixed! :-)

[TheBlueMatt]

tiny nit: I might prefer this if it kept the benchmarked-against data on stack instead of heap, but it doesnt matter much.

[sipa]

std::array stores on the stack

[TheBlueMatt]

static implies not-on-stack, no?

[sipa]

@TheBlueMatt static const is just statically allocated by the binary, not even on the heap.

[TheBlueMatt]

Yes, indeed, my point was to prefer stack over binary or other allocations. It shouldnt matter cause the memory usage of these benchmarks should be trivial, so whatever, it doesnt matter.

[jonasschnelli]

utACK dcc0e0f

[paveljanik]

OS X, Apple LLVM version 7.0.2:

  CXX      bench/bench_bench_bitcoin-verify_script.o
bench/verify_script.cpp:58:48: error: implicit instantiation of undefined template 'std::__1::array<unsigned char, 32>'
    static const std::array<unsigned char, 32> vchKey = {
                                               ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__tuple:95:65: note: template is declared here
template <class _Tp, size_t _Size> struct _LIBCPP_TYPE_VIS_ONLY array;
                                                                ^
1 error generated.

[practicalswift]

@paveljanik Missing #include <array> added. Thanks for reviewing! :-)

[paveljanik]

utACK 6835cb0

[sipa]

utACK 6835cb0

[TheBlueMatt]

utACK 6835cb0