Libraries: Use correct type ; avoid compiler warnings. #12351

pull murrayn wants to merge 1 commits into bitcoin:master from murrayn:ptrdiff_t changing 1 files +3 −3

murrayn commented at 10:58 AM on February 5, 2018: contributor

ptrdiff_t is a more strictly correct type, and gets rid of compiler warnings.
Use ptrdiff_t type to more precisely indicate usage and avoid compiler warnings. a25cb0f313
fanquake added the label Refactoring on Feb 5, 2018
MarcoFalke commented at 12:28 PM on February 5, 2018: member

Duplicate of #12286
MarcoFalke marked this as duplicate on Feb 5, 2018
murrayn commented at 12:01 AM on February 6, 2018: contributor

I wasn't aware of another PR dealing with the compiler warnings. However, the solutions are not duplicates. I think changing the type to ptrdiff_t as I do here is more correct than the casting solution. The cast solution is just masking the problem.
murrayn renamed this:
~~Libraries: Use type more precisely indicating usage and avoid compilers warnings.~~
Libraries: Use correct type ; avoid compiler warnings.
on Feb 7, 2018
devrandom commented at 4:42 PM on February 8, 2018: none

utACK https://github.com/bitcoin/bitcoin/pull/12351/commits/a25cb0f313315bd987834aa5f500b5682a9c3cd5
laanwj commented at 7:44 PM on February 8, 2018: member

utACK https://github.com/bitcoin/bitcoin/pull/12351/commits/a25cb0f313315bd987834aa5f500b5682a9c3cd5
laanwj commented at 7:46 PM on February 8, 2018: member

One question though, for @sipsorcery maybe - is ptrdiff_t supported with MSVC? We're not using it anywhere and I remember problems with ssize_t.
practicalswift commented at 9:08 PM on February 8, 2018: contributor

utACK a25cb0f313315bd987834aa5f500b5682a9c3cd5
Empact commented at 9:22 PM on February 8, 2018: member

@laanwj Untested but they list it as of VS2008: https://msdn.microsoft.com/en-us/library/323b6b3k(v=vs.90).aspx
Empact commented at 9:48 PM on February 8, 2018: member

utACK a25cb0f

I prefer this over #12286
sipsorcery commented at 9:51 PM on February 8, 2018: member

@laanwj ptrdiff_t is defined in vcruntime.h with MSVC. This change builds with Visual Studio.
laanwj commented at 10:37 AM on February 12, 2018: member

@sipsorcery Thanks for checking!

in src/key.cpp:69 in a25cb0f313

  65 | @@ -66,7 +66,7 @@ static int ec_privkey_import_der(const secp256k1_context* ctx, unsigned char *ou
  66 |      if (end - privkey < 2 || privkey[0] != 0x04u) {
  67 |          return 0;
  68 |      }
  69 | -    size_t oslen = privkey[1];
  70 | +    ptrdiff_t oslen = privkey[1];

laanwj commented at 10:40 AM on February 12, 2018:

Checked that neither of the values whose type changed can ever be negative, or overflow, given that the range of privkey[x] is 0..255.

laanwj merged this on Feb 12, 2018
laanwj closed this on Feb 12, 2018
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