Rust Cross Reference with MISRA C 2025

The following tables provide a cross reference between the MISRA C 2025 guidelines and their applicability to Rust. The first table covers guidelines that are applicable to Rust in general, while the second table covers additional guidelines that are applicable in the presence of unsafe code. The third table lists guidelines that are not applicable to Rust.

The origin of this assessment can be found at MISRA C:2025 Addendum 6.

Table 1 – Guidelines applicable to Rust in general (safe Rust, no unsafe code present)

Guideline	Category	Safety critical Rust rule	Category	Comment
Directives
D.1.1	Required
D.1.2	Advisory			intended to apply to experimental and unstable features, forcing full documentation
D.2.1	Required
D.3.1	Required
D.4.1	Required			often in the form of panics
D.4.4	Advisory			conditional compilation is provided by the cfg attribute
D.4.5	Advisory			“ambiguity” is determined by the project
D.4.7	Required			prefer Option, Result, etc. over in-band error values
D.4.9	Advisory
D.4.11	Required
D.4.12	Required
D.4.13	Advisory			many Rust APIs use the type system to enforce ordering
D.4.14	Required
D.4.15	Required			Rust implements IEEE-754
D.5.2	Required
D.5.3	Required
Rules
R.1.3	Required
R.1.5	Required			this applies to deprecated APIs
R.2.1	Required
R.2.2	Required
R.2.3	Advisory
R.2.5	Advisory
R.2.6	Advisory
R.2.7	Advisory
R.2.8	Advisory
R.3.1	Required			nested comments are fully supported
R.5.2	Required			no character limit, but one can be applied; has name spaces
R.5.3	Required	Names in a macro definition... (gui_SJMrWDYZ0dN4)	Required	this also applies to macro names
R.5.6	Required			the proper module system makes surprise name conflicts much less likely
R.5.8	Required			the proper module system makes surprise name conflicts much less likely
R.5.9	Advisory
R.7.1	Required			Rust octals have a distinct prefix from decimals
R.7.2	Required			this is an error by default but can be enabled. Note that suffixes also make the size explicit
R.8.7	Advisory			items should not be declared pub if referenced in only one module
R.8.9	Advisory
R.8.13	Advisory			mut should be avoided unless necessary
R.9.1	Mandatory			enforced by rustc but can be bypassed by unsafe
R.9.4	Required			enforced by rustc
R.11.3	Required
R.11.4	Advisory	An integer shall not be con... (gui_PM8Vpf7lZ51U)	<TODO>
R.11.11	Advisory			enforced by rustc
R.12.1	Advisory
R.13.1	Required			order of evaluation is strict in Rust
R.13.5	Required
R.14.3	Required
R.14.4	Required			enforced by rustc
R.15.4	Advisory
R.15.5	Advisory
R.15.7	Required
R.17.2	Required	Recursive function are not ... (gui_ot2Zt3dd6of1)	Required
R.17.7	Required			must_use can help indicate where this is important, but does not affect applicability
R.17.8	Advisory			this cannot be done accidentally without declaring parameters mut
R.17.11	Advisory			a non-returning function can be declared to return a value type
R.18.3	Required
R.18.5	Advisory
R.19.2	Advisory	Ensure reads of union field... (gui_0cuTYG8RVYjg)	Required
R.19.3	Required
R.21.25	Required
R.22.13	Required
R.22.18	Required
R.22.19	Required

Table 2 – Guidelines applicable to Rust in the presence of unsafe code

In addition to the rules from Table 1, these are the additional guidelines that need to be covered:

Guideline	Category	Safety critical Rust rule	Category	Comment
Directives
D.4.2	Advisory
D.4.3	Required
D.5.1	Required			not all safe Rust types are race-free
Rules
R.1.1	Required
R.5.1	Required			no character limit, except in extern “C”, but one can be set by project
R.5.5	Required			macros and functions use different syntax
R.5.10	Required			only possible in some cases. Previously Rule 21.2
R.8.3	Required			an extern declaration shall have a type compatible with the C declaration
R.8.5	Required			may affect extern “C” declarations
R.8.6	Required			may affect extern “C” declarations
R.8.15	Required			may affect extern “C” declarations
R.8.17	Advisory			alignment applies to types, not objects
R.9.7	Mandatory
R.10.5	Advisory	The 'as' operator should no... (gui_ADHABsmK9FXz)	Advisory	includes both safe as and unsafe transmute operations
R.10.8	Required	Avoid as underscore pointer... (gui_HDnAZ7EZ4z6G)	Required	includes both safe as and unsafe transmute operations
R.11.1	Required			includes both safe as and unsafe transmute operations
R.11.2	Required
R.11.5	Advisory
R.11.6	Required	An integer shall not be con... (gui_PM8Vpf7lZ51U)	<TODO>
R.11.8	Required
R.12.2	Required	Avoid out-or-range shifts (gui_LvmzGKdsAgI5), Do not shift an expression ... (gui_RHvQj8BHlz9b)	Mandatory, Advisory
R.12.4	Advisory			this is either well-defined or will not occur
R.14.1	Required			applies to while loops only
R.17.9	Mandatory			this is expressed with the ! (Never) type, and enforced by rustc
R.18.1	Required			by unsafe API
R.18.2	Required			by unsafe API
R.18.4	Advisory			applies to use of the unsafe API
R.18.6	Required
R.19.1	Mandatory
R.20.4	Required			possible with raw identifiers but the compiler prevents visual conflicts
R.20.7	Required			possible to express with procedural macros only, not macro_rules
R.21.3	Required			only accessible through unsafe extern “C”
R.21.4	Required			only accessible through unsafe extern “C”
R.21.5	Required			only accessible through unsafe extern “C”
R.21.6	Required			only accessible through unsafe extern “C”
R.21.7	Required			only accessible through unsafe extern “C”
R.21.8	Required			only accessible through unsafe extern “C”
R.21.9	Required			only accessible through unsafe extern “C”
R.21.10	Required			only accessible through unsafe extern “C”
R.21.12	Required			only accessible through unsafe extern “C”
R.21.13	Mandatory			only accessible through unsafe extern “C”
R.21.14	Required			only accessible through unsafe extern “C”
R.21.15	Required			only accessible through unsafe extern “C”
R.21.16	Required			only accessible through unsafe extern “C”
R.21.17	Mandatory			only accessible through unsafe extern “C”
R.21.18	Mandatory			only accessible through unsafe extern “C”
R.21.19	Mandatory			only accessible through unsafe extern “C”
R.21.20	Mandatory			only accessible through unsafe extern “C”
R.21.21	Required			only accessible through unsafe extern “C”
R.21.24	Required			only accessible through unsafe extern “C”
R.21.26	Required			only accessible through unsafe extern “C”
R.22.1	Required			applies to resources acquired through FFI only
R.22.2	Mandatory			only accessible through unsafe extern “C”
R.22.3	Required			only accessible through unsafe extern “C”
R.22.4	Mandatory			only accessible through unsafe extern “C”
R.22.5	Mandatory			only accessible through unsafe extern “C”
R.22.6	Mandatory			only accessible through unsafe extern “C”
R.22.7	Required			only accessible through unsafe extern “C”
R.22.8	Required			only accessible through unsafe extern “C”
R.22.9	Required			only accessible through unsafe extern “C”
R.22.10	Required			only accessible through unsafe extern “C”
R.22.11	Required
R.22.12	Mandatory			only accessible through unsafe extern “C”
R.22.14	Mandatory			applies to creating synchronization objects before threads that use them
R.22.15	Required			applies to releasing synchronization objects after threads that use them
R.22.16	Required			only accessible through unsafe extern “C”
R.22.17	Required			only accessible through unsafe extern “C”
R.22.20	Mandatory

Table 3 – Guideline rules that are not applicable to Rust

Guideline	Category	Comment
Directives
D.4.6	Advisory	all primitive types already fulfil this
D.4.8	Advisory
D.4.10	Required
Rules
R.1.4	Required	this is specific to C versioning
R.2.4	Advisory	no separate tag name space in Rust
R.3.2	Required
R.4.1	Required
R.4.2	Advisory
R.5.4	Required
R.5.7	Required	no separate tag name space in Rust
R.6.1	Required	only provided as a library feature
R.6.2	Required
R.6.3	Required
R.7.3	Required
R.7.4	Required
R.7.5	Mandatory
R.7.6	Required
R.8.1	Required
R.8.2	Required
R.8.4	Required
R.8.8	Required
R.8.10	Required
R.8.11	Advisory
R.8.12	Required
R.8.14	Required
R.8.16	Advisory	cannot be explicitly specified. Only ZSTs have this alignment
R.8.18	Required
R.8.19	Advisory
R.9.2	Required
R.9.3	Required
R.9.5	Required
R.9.6	Required
R.10.1	Required
R.10.2	Required
R.10.3	Required
R.10.4	Required
R.10.6	Required
R.10.7	Required
R.11.9	Required	Rust does not have a null pointer constant (specific concept to C)
R.11.10	Required
R.12.3	Advisory
R.12.5	Mandatory
R.12.6	Required
R.13.2	Required	order of evaluation is strict in Rust
R.13.3	Advisory
R.13.4	Advisory	result has unit type and order of evaluation is strict in Rust
R.13.6	Required	this is not an expression operator in Rust
R.14.2	Required
R.15.1	Advisory
R.15.2	Required
R.15.3	Required
R.15.6	Required
R.16.1	Required
R.16.2	Required
R.16.3	Required
R.16.4	Required	a corresponding match expression must be complete
R.16.5	Required	irrefutable pattern causes a subsequent refutable one to be unreachable
R.16.6	Required
R.16.7	Required
R.17.1	Required
R.17.3	Mandatory
R.17.4	Mandatory	the return keyword is not needed to return a value in Rust, only to exit
R.17.5	Required
R.17.10	Required
R.17.12	Advisory
R.17.13	Required
R.18.7	Required
R.18.8	Required
R.18.9	Required
R.18.10	Mandatory
R.20.1	Advisory	rules specific to the C preprocessor do not apply to Rust
R.20.2	Required
R.20.3	Required
R.20.5	Advisory
R.20.6	Required
R.20.8	Required
R.20.9	Required
R.20.10	Advisory
R.20.11	Required
R.20.12	Required
R.20.13	Required
R.20.14	Required
R.20.15	Required
R.21.11	Advisory	no external interface
R.21.22	Mandatory	no external interface
R.21.23	Required	no external interface
R.23.1	Advisory
R.23.2	Required
R.23.3	Advisory
R.23.4	Required
R.23.5	Advisory
R.23.6	Required
R.23.7	Advisory
R.23.8	Required

Glossary

Category

Each MISRA C guideline is assigned a category, as follows:

Category	Interpretation
Mandatory	Code shall always comply with this guideline. Formal deviation is not permitted
Required	Code shall comply with this guideline, with a formal deviation required where this is not the case
Advisory	These are recommendations which should be followed as far as is reasonably practical. Formal deviation is not necessary for advisory guidelines but, if the formal deviation process is not followed, alternative arrangements should be made for documenting non-compliances

Footnotes

Footnotes