[API] fix sign-conversion warnings in span & trace id

[sjanel]

Changes

Fix some warnings appearing with -Wsign-conversion:

opentelemetry_cpp-src/api/include/opentelemetry/trace/span_id.h:34:20: warning: conversion to ‘size_t’ {aka ‘long unsigned int’} from ‘int’ may change the sign of the result [-Wsign-conversion]
   34 |       buffer[i * 2 + 0] = kHex[(rep_[i] >> 4) & 0xF];
      |              ~~~~~~^~~
opentelemetry_cpp-src/api/include/opentelemetry/trace/span_id.h:35:20: warning: conversion to ‘size_t’ {aka ‘long unsigned int’} from ‘int’ may change the sign of the result [-Wsign-conversion]
   35 |       buffer[i * 2 + 1] = kHex[(rep_[i] >> 0) & 0xF];
      |              ~~~~~~^~~

api/include/opentelemetry/trace/trace_id.h:40:20: warning: conversion to ‘size_t’ {aka ‘long unsigned int’} from ‘int’ may change the sign of the result [-Wsign-conversion]
   40 |       buffer[i * 2 + 0] = kHex[(rep_[i] >> 4) & 0xF];
      |              ~~~~~~^~~
api/include/opentelemetry/trace/trace_id.h:41:20: warning: conversion to ‘size_t’ {aka ‘long unsigned int’} from ‘int’ may change the sign of the result [-Wsign-conversion]
   41 |       buffer[i * 2 + 1] = kHex[(rep_[i] >> 0) & 0xF];
      |              ~~~~~~^~~
opentelemetry_cpp-src/api/include/opentelemetry/nostd/string_view.h:127:21: warning: conversion to ‘opentelemetry::v1::nostd::string_view::size_type’ {aka ‘long unsigned int’} from ‘long int’ may change the sign of the result [-Wsign-conversion]
  127 |         res = found - data();
      |               ~~~~~~^~~~~~~~
opentelemetry_cpp-src/api/include/opentelemetry/nostd/internal/absl/types/../types/internal/variant.h:48:56: warning: unsigned conversion from ‘int’ to ‘absl::otel_v1::internal::identity_t<long unsigned int>’ {aka ‘long unsigned int’} changes value from ‘-1’ to ‘18446744073709551615’ [-Wsign-conversion]
   48 | OTABSL_INTERNAL_INLINE_CONSTEXPR(size_t, variant_npos, -1);
      |                                                        ^~

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: sjanel / name: Stephane Janel (f723523)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.95%. Comparing base (bed305f) to head (f723523).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3761   +/-   ##
=======================================
  Coverage   89.95%   89.95%           
=======================================
  Files         225      225           
  Lines        7158     7158           
=======================================
  Hits         6438     6438           
  Misses        720      720           

Files with missing lines	Coverage Δ
...metry/nostd/internal/absl/types/internal/variant.h	77.36% <ø> (ø)
api/include/opentelemetry/nostd/string_view.h	98.15% <100.00%> (ø)
api/include/opentelemetry/trace/span_id.h	100.00% <100.00%> (ø)
api/include/opentelemetry/trace/trace_id.h	100.00% <100.00%> (ø)

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[marcalff]

Thanks for the fix, see comments.

[marcalff]

Since the original issue is about sign, how about changing variable i to unsigned in the for loop ?

[sjanel]

Done, plus two other similar warnings.

[marcalff]

LGTM, thanks for the fix.