Merge #18468: Span improvements

26acc8dd9b512f220c1facdba2c5de7976d3c258 Add sanity check asserts to span when -DDEBUG (Pieter Wuille)
2676aeadfa0e43dcaaccc4720623cdfe0beed528 Simplify usage of Span in several places (Pieter Wuille)
ab303a16d114b1e94c6cf0e4c5db5389dfa197f6 Add Span constructors for arrays and vectors (Pieter Wuille)
bb3d38fc061d8482e68cd335a45c9cd8bb66a475 Make pointer-based Span construction safer (Pieter Wuille)
1f790a1147ad9a5fe06987d84b6cd71f91cbec4b Make Span size type unsigned (Pieter Wuille)

Pull request description:

  This improves our Span class by making it closer to the C++20 `std::span` one:
  * ~~Support conversion between compatible Spans (e.g. `Span<char>` to `Span<const char>`).~~ (done in #18591)
  * Make the size type `std::size_t` rather than `std::ptrdiff_t` (the C++20 one underwent the same change).
  * Support construction of Spans directly from arrays, `std::string`s, `std::array`s, `std::vector`s, `prevector`s, ... (for all but arrays, this only works for const containers to prevent surprises).

  And then make use of those improvements in various call sites.

  I realize the template magic used looks scary, but it's only needed to make overload resultion make the right choices. Note that the operations done on values are all extremely simple: no casts, explicit conversions, or warning-silencing constructions. That should hopefully make it simpler to review.

ACKs for top commit:
  laanwj:
    Code review ACK 26acc8dd9b512f220c1facdba2c5de7976d3c258
  promag:
    Code review ACK 26acc8dd9b512f220c1facdba2c5de7976d3c258.

Tree-SHA512: 5a5bd346a140edf782b5b3b3f04d9160c7b9e9def35159814a07780ab1dd352545b88d3cc491e0f80d161f829c49ebfb952fddc9180f1a56f1257aa51f38788a

2 files changed, 4 insertions, 4 deletions

diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index ed0175bb10..7a5421ab6f 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -139,7 +139,7 @@ std::string DescriptorChecksum(const Span<const char>& span)
     return ret;
 }
 
-std::string AddChecksum(const std::string& str) { return str + "#" + DescriptorChecksum(MakeSpan(str)); }
+std::string AddChecksum(const std::string& str) { return str + "#" + DescriptorChecksum(str); }
 
 ////////////////////////////////////////////////////////////////////////////
 // Internal representation                                                //
@@ -1087,7 +1087,7 @@ bool CheckChecksum(Span<const char>& sp, bool require_checksum, std::string& err
 
 std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out, std::string& error, bool require_checksum)
 {
-    Span<const char> sp(descriptor.data(), descriptor.size());
+    Span<const char> sp{descriptor};
     if (!CheckChecksum(sp, require_checksum, error)) return nullptr;
     auto ret = ParseScript(0, sp, ParseScriptContext::TOP, out, error);
     if (sp.size() == 0 && ret) return std::unique_ptr<Descriptor>(std::move(ret));
@@ -1098,7 +1098,7 @@ std::string GetDescriptorChecksum(const std::string& descriptor)
 {
     std::string ret;
     std::string error;
-    Span<const char> sp(descriptor.data(), descriptor.size());
+    Span<const char> sp{descriptor};
     if (!CheckChecksum(sp, false, error, &ret)) return "";
     return ret;
 }
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 23d5b72a5c..9415bba585 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1522,7 +1522,7 @@ static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CS
 static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
 {
     CScript scriptPubKey;
-    Span<const valtype> stack = MakeSpan(witness.stack);
+    Span<const valtype> stack{witness.stack};
 
     if (witversion == 0) {
         if (program.size() == WITNESS_V0_SCRIPTHASH_SIZE) {