Fix MISRA C++ 2023 rule 7.0.3 "The numerical value of a character shall not be used"

[mohammedRafeeque]

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

Describe the bug
2 Misra warnings are getting reported for rule MISRACPP2023-7_0_3-a

1. for (char character : value)
2. m_buffer.at(m_len) = 0;

<style> </style>

SNo	Rule	Severity	Message	Filename	Linenumber
1298	MISRACPP2023-7_0_3-a	2	The plain char type shall be initialized only by character values	/zserio_runtime/zserio/JsonEncoder.cpp	55
1244	MISRACPP2023-7_0_3-a	2	To the plain char type assign only character values	/zserio_runtime/zserio/CppRuntimeException.cpp	42

Please check possibility of fixing the same.

Steps to reproduce the behavior:
SCA run using MISRA 2023 configuration.

Expected behavior
No SCA warnings for MISRA 2023 ruleset

Additional context
N.A

@Roland-Homeier @mikir FYI.

[Mi-La]

We will enable rule S810.

[Mi-La]

We don't understand the issue in JsonEncoder.cpp, seems to be almost false positive and moreover the sonar rule is not catching it.
Tried to fix CppRuntimeException by returning '\0' instead of 0.

Some issues were accepted as exceptions - see SonarCloud.

[mohammedRafeeque]

In latest main we are still getting 19 warning.

Date: 6 days ago (8/13/2024 1:00:38 PM)
Commit hash: 009d16a

<style> </style>

SNo	Rule	Severity	Message	Filename	Linenumber
1527	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'unsigned int'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	48
1526	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	48
1525	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'unsigned long'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	48
1524	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'unsigned int' to type 'char'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	48
1523	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'int' to type 'char'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	48
1522	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'unsigned long' to type 'char'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	48
1505	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'int' to type 'value_type'	/zserio_runtime/include/roadgraph_reliable/zserio_runtime/zserio/StringConvertUtil.h	36
1304	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'uint8_t'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	92
1300	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'uint8_t'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	91
1295	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'uint8_t'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	85
1293	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	80
1292	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	76
1291	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	72
1290	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	68
1289	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	64
1288	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	60
1287	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	59
1286	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'int'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/JsonEncoder.cpp	57
1172	MISRACPP2023-7_0_3-a	2	There shall be no conversion from type 'char' to type 'uint8_t'	/zserio_runtime/src/roadgraph_reliable/zserio_runtime/zserio/BitStreamWriter.cpp	506

@mikir Can you please check.

[mikir]

We have fixed all issues found by SonarCloud rule S810.