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Questions tagged [misra]

Use this tag for questions about code that must conform to the coding guidelines called MISRA-C and MISRA-C++.

MISRA Homepage

Document full titles:

  • Guidelines for the use of the C language in critical systems
  • Guidelines for the use of the C++ language in critical systems

Originally written by-and-for the automotive industry, now more widely used, including in the aerospace and defence industries.

Three editions of the C guidelines exist:

  • MISRA-C:1998 - 1st Edition (informally MISRA C1).
    Compatible with C90 only.
  • MISRA-C:2004 - 2nd Edition (informally MISRA C2).
    Compatible with C90 only.
  • MISRA C:2012 - 3rd Edition (informally MISRA C3).
    Released at Embedded World 2013. Compatible with C90 and C99.

An updated MISRA C:2012, 3rd Edition, 1st Revision (informally MISRA C3.1) was released at Embedded World 2019, incorporating Amendment 1 and Technical Corrigendum 1.

MISRA C:2012 Amendment 2 (published February 2020) brings C11 and C17 into scope (albeit with some restrictions).

MISRA C:2012 is the current industry de facto standard and the one recommended to use. The older ones are still available, but not recommended for new projects.

MISRA-C++ only exists in its current revision, MISRA-C++:2008.

Tag usage: Use this tag for all questions related to MISRA C and MISRA C++. It shall always be used together with either the or the tag.

When asking about the MISRA rules, please specify exactly which version you are using: C:1998, C:2004, C:2012 or C++:2008.

421 questions
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What is the correct way to initialize C++ structures with unions?

The MISRA-C++ rule 8-5-2 requires that C++ structures are initialized with the correct braces. I have a structure with unions and I connot find the correct combination of braces to satisfy this rule. I am not sure if my code is incorrect or false…
amanning
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How to cast unsigned integer to enum using CMSIS API

I am using CMSIS API in my C program for ARM Cortex-M CPU. CMSIS defines NVIC_DisableIRQ function as __STATIC_INLINE void __NVIC_DisableIRQ(IRQn_Type IRQn); IRQn_Type is a typedef enum, like typedef enum IRQn { NonMaskableInt_IRQn =…
ilia
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MISRA 5-2-1 rule requires postfix-expressions?

The rule 5-2-1 in MISRA-2008 states that Each operand of a logical && or || shall be a postfix-expression. Exception: Where an expression consists of either a sequence of only logical && or a sequence of only logical ||, extra parentheses are not…
john c. j.
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A cast should not be performed between a pointer type and an integral type

I am performing a pointer assignment in an Embedded C script like so: uint32_T *a = (uint32_T *) (4096U); Basically, I need a to point to the address location 4096 (decimal) I get the MISRA warning as specified in the title (I use Code Composer…
ANUBHAV DINKAR
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Is it legal write to a byte array in a union and read from an int to convert values in MISRA C?

I guess this must have been asked before, but I could not get a specific yes/no answer. I have this code snippet : union integer_to_byte { signed int IntPart; unsigned char BytePart[2]; }; typedef union integer_to_byte I2B; main() { …
EmbSysDev
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3 answers

C struct information hiding (Opaque pointer)

I'm currently a bit confused regarding the concept of information hiding of C-structs. The backround of this question is an embedded c project with nearly zero knowledge of OOP. Up until now I always declared my typedef structs inside the header…
Evox402
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Avoiding exceptions in default parameters

I have a function declaration like this: void foo(std::string const &bar = std::string("")); Now, we are using MISRA C++, and our code verifier gives an error on the default value's constructor: RULE 15-5-3: The terminate() function shall not be…
Ken Y-N
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Which C++ standard library functions allocate memory?

It's obvious that the collection classes with their class Allocator = std::allocator parameter explicitly use heap allocations, but which other library functions (or indeed language features) can be expected to allocate memory in a practical…
Ken Y-N
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3 answers

Use of #define to alias structure members

This is a subjective question, so I will accept 'there is no answer' but read fully as this is specifically on a system where the code is safety critical. I've adopted some embedded C code for a safety critical system, where the original author has…
Jay M
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Unpermitted operand to operator '>>' and '&' (MISRA C)

When checking some code with Misra, it has generated following messages Unpermitted operand to operator '>>' [MISRA 2012 Rule 10.1 required] Unpermitted operand to operator '&' [MISRA 2012 Rule 10.1 required] I wasn't able to understand the issue,…
user145760
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How to resolve MISRA C:2012 Rule 13.2 and 13.3 for C code?

I have C source code and I am making it MISRA Compliant. I got an following errors related to MISRA 2012 Rule 13.3 and 13.2: increment/decrement operation combined with other operation with side-effects [MISRA 2012 Rule 13.3, advisory]buf[count++]…
raj123
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Is declaring a variable inside an if statement in c a bad habit?

My assumption is that this is going to mess with checkers and stack analysis. I can't prove my assumption and I don't think C99 will complain. Probably neither c89 will because the definition is immediately after the opening of the curly brace: …
Catosh
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Is it possible to disable MISRA checks of external libraries?

Is it possible to disable MISRA checks of external libraries? I've tried this, but it doesn't seem to work (this header uses C++ style comments and incompatible @ tags). #pragma ghs startnomisra #include #pragma ghs endnomisra Update…
Minor Threat
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MISRA C:2004 10.5 Query

I am somewhat stucked at a part of the code that gives MISRA C 2004 10.5 violation but am not able to figure out what exactly might be the cause. I have defined this MACRO to get the power of 2. The code which shows the violation is #define…
Ankit Shah
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MISRA 2012 rule 8.10 static inline

Why does MISRA recommends that an inline function be declared with static storage class? While the keyword inline is a hint to the compiler to replace all function calls with the actual function body, and the compiler may or may not perform it, how…
Girish Onte
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