Fix all sign-conversion warnings reported by gcc compiler

[mohammedRafeeque]

Zserio version and language
Zserio: latest from master
Commit date: 6 days ago (6/4/2024 7:12:28 PM)
Commit hash: b8cc6c0

Language: C++

Describe the bug

Followup of old issue #579
Getting the bellow errors related to -Wconversion.

1. zserio_runtime/zserio/FloatUtil.cpp:68:33: error: conversion to 'unsigned int' from 'int' may change the sign of the result [-Werror=sign-conversion]
   exponent32 = exponent16 - FLOAT16_EXPONENT_BIAS + FLOAT32_EXPONENT_BIAS;
   ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
   cc1plus: all warnings being treated as errors
2. zserio_runtime/zserio/BitStreamWriter.cpp:659:90: error: conversion to 'std::array<long unsigned int, 8>::size_type' {aka 'long unsigned int'} from 'int' may change the sign of the result [-Werror=sign-conversion]
   const uint8_t add = static_cast<uint8_t>((value >> shiftBits) & bitMasks[numBits - 1]);
   ~~~~~~~~^~~
   cc1plus: all warnings being treated as errors

How to reproduce
Steps to reproduce the behavior:
used gcc version
gcc --version
gcc (Ubuntu 8.4.0-3ubuntu2) 8.4.0

Expected behavior
No compilation warnings

@mikir Please check

[mikir]

It seems to me that the reported warnings are related to the -Wsign-conversion option and not to -Wconversion option. Is it correct? Does it mean that you request to enable another -Wsign-conversion gcc option as well and investigate/fix all possible reported warnings?

[mohammedRafeeque]

Yes, you are right, reported warnings are related to the -Wsign-conversion option.
Yes, for direct integration of Zserio runtime lib without any manual adaptations,request to enable another -Wsign-conversion gcc option as well.
For zserio runtime lib only two warning instance only observed.
@Roland-Homeier : FYI

[mikir]

Yes, you are right, reported warnings are related to the -Wsign-conversion option. Yes, for direct integration of Zserio runtime lib without any manual adaptations,request to enable another -Wsign-conversion gcc option as well. For zserio runtime lib only two warning instance only observed.

OK, thanks for the clarification. We will do it within the current milestone.

[mikir]

Please note that there is a bug till gcc version 9.3.0 which caused sign-conversion warning even if it is fixed (for more info please see the bug report).