Static Analysis

Note

The CODESYS Professional Developer Edition provides a tool for static code analysis. A rule set is included for automatically checking the naming convention described above.

Under some circumstances it would be necessary to deactivate a specific rule. This can be achieved with a pair of attributes.

{analysis -46}
/// ...
/// some code which does not conforme to rule SA0046
/// ...
{analysis +46}

PLCopen - Coding Guidelines

The official PLCopen document Coding Guidelines summarises the results of the PLCopen workgroup Software Construction Guidelines Task Force Coding Guidelines. It's first official published version dates from April 20, 2016. The aim of this guidelines is to define a set of rules and to provide a PLCopen proposal how these rules can be used.

Please take a look to the homepage of the PLCopen for the related documents.

Every Rule has an classification number, as shown hereunder:

Rule	CODESYS	Name	Comment
N1	SA0047	Avoid physical addresses
N2		Define type prefixes for Variables	see: Naming Conventions
N3		Define the names to avoid	see: Forbidden Symbols
N4		Define the use of case (capitals)
N5	SA0013	Local names shall not shadow global names
N6	SA0101	Define an acceptable name length
N7		Define naming rules for namespaces	see: Namespace
N8		Define the acceptable character set	see: Allow unicode characters for identifiers
N9	SA0013, SA0027	Different element types should not bear the same name
N10		Define name prefixes for user defined types	see: Description of the prefix for a data type
C1		Comments shall describe the intention of the code
C2	SA0162	All elements shall be commented
C3	SA0163	Avoid nested comments
C4	SA0140	Comments may not include code	Exception, see: Literal Blocks
C5	SA0164	Use single line comments	see: LibDocContent
C6		Define comments language	Library developer employed by 3S use English for their comments
CP1	SA0047, SA0048	Access to a member shall be by name
CP2	SA0001, SA0031	All code shall be used in the application
CP3		All variables shall be initialized before being used	see: CODESYS initialize all variables with all bits zero by default
CP4	SA0028	Direct addressing should not overlap
CP5		Applications shall be well designed
CP6		Avoid external variables in functions and function blocks
CP7	SA0009	Error information shall be tested
CP8	SA0054	Floating point comparison shall not be equality or inequality
CP9	SA0150	Limit the complexity of POU code	see: Static Analysis - Metrics in the OnlineHelp
CP10	SA0006	Avoid multiple writes from multiple tasks
CP11		Manage synchronization among tasks	see: CAA_types.library BOLT, SEMA
CP12	SA0004	Physical outputs shall be written once per PLC cycle
CP13	SA0160	POUs shall not call themselves directly or indirectly
CP14	SA0090	POUs shall have a single point of exit
CP15		Read a variable written by another task only once per cycle
CP16	SA0165	Tasks shall only call program POUs and not Function Blocks
CP17	SA0009	Usage of parameters shall match their declaration mode
CP18	SA0121	Use of global variables shall be limited
CP19		Usage of jump and return should be avoided
CP20	SA0105	Function block instances should be called only once
CP21	SA0073	Use VAR_TEMP for temporary variable declaration
CP22	SA0011, SA0033	Select appropriate data type
CP23	SA0166	Define maximum number of input/output/in-out variables of a POU
CP24	SA0032, SA0033, SA0035, SA0036	Do not declare variables that are not used
CP25	SA0019	Data types conversion should be explicit
CP26	SA0043	A global variable may be written only by one PROGRAM
CP27		Avoid deprecated features
CP28		Time and physical measures comparison shall not be equality or inequality
L1		Define indentation	Library developer employed by 3S use four spaces
L2		(FBD) Avoid assignments of intermediate results within networks
L3		(FBD) Define maximum complexity of single network
L4		(LD) A coil should not be followed by a contact
L5		(LD) Define maximum rung complexity
L6		(SFC) Closing divergent paths
L7		(SFC) Do not program an SFC action block in SFC
L8		(SFC) Define maximum complexity
L9		(ST) Define general formatting rules
L10		(ST) Usage of CONTINUE and EXIT instruction should be avoided
L11		(ST) Define the maximum line length
L12	SA0072	(ST) Loop variables should not be modified inside a FOR loop
L13	SA0073	(ST) FOR loop variable usage should not be used outside the FOR loop
L14		(ST) Passing parameters should be clear
L15		(ST) Use parenthesis to explicitly express operation precedence
L16		(ST) Define the use of tabs	Library developer employed by 3S don't use tabs
L17	SA0075	(ST) Each IF instruction should have an ELSE clause
E1		Dynamic memory allocation shall not be used
E2	SA0061	Pointer arithmetic shall not be used
E3	SA0061	Some comparator instructions shall not be used for pointers or reference manipulation

Recommended Rules for Static Analysis

Available Rules

This table shows the set of recommended rules that should be activated or deactivated in CODESYS Static Analysis.

Rule	PLCopen	Description	Active	Reason
SA0001	CP2	Unreachable code	Yes
SA0002		Empty objects	Yes	[1]
SA0003		Empty statements	Yes
SA0004	CP12	Multiple write access on output	Yes	[2]
SA0005		Check address and data type	Yes
SA0006	CP10	Write access from several tasks	Yes	[3]
SA0007		Address operator on constants	Yes
SA0008		Check subrange types	Yes
SA0009	CP7, CP17	Unused return values	Yes
SA0010		Arrays with only one component	Yes
SA0011	CP22, CP24	Useless declarations	No
SA0012		Variables which could be declared as constants	Yes
SA0013	N5, N9	Declarations with the same variable name	not yet	[4]
SA0014		Assignment of instances	Yes
SA0015		Access to global data via FB_Init	Yes
SA0016		Gaps in structures	Yes
SA0017		Non-regular assignments	Yes
SA0018		Unusual bit access	Yes
SA0019	CP25	Implicit pointer conversions	not yet
SA0020		Possibly assignment of truncated value to REAL variable	Yes	[5]
SA0021		Transporting the address of a temporary variable	Yes
SA0022		(Possibly) unassigned return value	Warning
SA0023		Too big return values	Warning
SA0024		Untyped literals / constants	No
SA0025		Unqualified enumeration constants	Yes
SA0026		Possible truncated strings	Yes
SA0027	N9	Multiple uses of identifiers	not yet	[6]
SA0028	CP4	Overlapping memory areas	Yes
SA0029		Notation in code different to declaration	Yes
SA0030		Unused objects	No
SA0031	CP2	Unused signatures	No	[12]
SA0032	CP24	Unused enumeration constants	No	[12]
SA0033	CP22, CP24	Unused variables	Warning
SA0034		Enumerations with incorrect assignment	Yes
SA0035	CP24	Unused input variables	No	[12]
SA0036	CP24	Unused output variables	No	[12]
SA0037		Write access to input variable	No	[7]
SA0038		Read access to output variable	No	[8]
SA0039		Possible null pointer dereferences	Yes
SA0040		Possible division by zero	Yes
SA0041		Detect possible loop invariant code	Yes
SA0042		Usage of different access paths	No
SA0043	CP26	Use of a global variable in only one POU	Yes
SA0044		Declarations with reference to interface	Yes
SA0045		Conversions	Yes	See: SA0019, SA0130, ..., SA0134
SA0046		Possible use of not initialised interface	Yes
SA0047	N1, CP1	Accesses to direct address	Yes
SA0048	N1, CP1	AT-declarations on direct addresses	Yes
SA0049		Usage of direct addresses	Yes	See: SA0005, SA0047, SA0048
SA0050		Rules for operators	Yes	See: SA0051, ..., SA0066
SA0051		Comparison operations on BOOL vairables	Yes
SA0052		Unusual shift operation	Yes
SA0053		Too big bitwise shift	Yes
SA0054	CP8	Comparisons of REAL/LREAL for equality / inequality	Yes
SA0055		Unnecessary comparisons of unsigned operands	Yes
SA0056		Constant out of valid range	Yes
SA0057		Possible loss of decimal places	No	[9]
SA0058		Operations on enumeration variables	Yes
SA0059		Comparison operations always returning TRUE or FALSE	Yes
SA0060		Zero used as invalid operand	Yes
SA0061	E2, E3	Unusual operation on pointer	Yes
SA0062		Uses of TRUE or FALSE in expressions	Yes	[10]
SA0063		Possibly not 16-bit-compatible operations	Yes
SA0064		Addition of pointer	Yes
SA0065		Incorrect pointer addition to base size	Yes
SA0066		Uses of temporary results	Yes
SA0070		Rules for statements	Yes	See: SA0071, ..., SA0090
SA0071		FOR statements	Yes	See: SA0072, SA0073, SA0080, SA0081
SA0072	L12	Invalid uses of counter variable	Yes	[11]
SA0073	CP21, L13	Uses of inadequate counter variable	No
SA0074		CASE statement	Yes	See: SA0075, ..., SA0078
SA0075	L17	Missing ELSE	Warning
SA0076		Missing enumeration constant	Warning
SA0077		Type mismatches with CASE expression	Yes
SA0078		Missing CASE branches	Yes
SA0080		Loop index variable for array index exeeds array range	Yes
SA0081		Upper border is not a constant	Yes
SA0090	CP14	Return statement before end of function	Warning
SA0095		Assignments in conditions	Yes
SA0100		Variables greater than 1024 bytes...	Yes
SA0101	N6	Names with invalid length	not yet
SA0102		Access to program/fb variables from the outside	Yes
SA0105	CP16, CP20	Multiple instance calls	Yes
SA0106		Virtual method calls in FB_INIT	No
SA0107		Missing formal parameters	No
SA0110		Check strict IEC rules	No	See: SA0111, ..., SA0123
SA0111		Pointer variables	No	[13]
SA0112		Reference variables	No	[13]
SA0113		Variables with data type WSTRING	No	[13]
SA0114		Variables with data type LTIME	No	[13]
SA0115		Variables with data type UNION	No	[13]
SA0117		Variables with data type BIT	No	[13]
SA0118		Initialisations not using constants	No	[13]
SA0119		Object-oriented features	No	[13]
SA0120		Program calls	Yes
SA0121	CP18	Missing VAR_EXTERNAL declarations	Yes
SA0122		Array index defined as expression	No	[13]
SA0123		Usages of INI, ADR or BITADR	No	[13]
SA0124		Prohibit dereference access in initialisations	No
SA0125		Prohibit references in initialisations	No
SA0130		Implicit expanding conversions	Yes
SA0131		Implicit narrowing conversions	Yes
SA0132		Implicit signed/unsigned conversions	Yes
SA0133		Explicit narrowing conversions	No
SA0134		Explicit signed/unsigned conversions	No
SA0140	C4	Statements commented out	Yes
SA0150	CP9	Violations of lower or upper limits or the metrics	No
SA0160	CP13	Recursive calls	Yes
SA0161		Unpacked structure in packed structure	Yes
SA0162	C2	Missing comments	No	[12]
SA0163	C3	Nested comments	Yes
SA0164	C5	Multiline comments	Yes
SA0165	CP16	Tasks calling other POUs than programs	No	[12]
SA0166	CP23	Max. number of input/output/in-out variables...	No
SA0167		Report Temporary FB Instances	?

Reasons for Exceptions

[1]

(1, )

[2]

(1, )

[3]

(1, )

[4]	(1, )SAN-45(1, )

[5]

(1, )

[6]

(1, )

[7]

(1, )

[8]

(1, )

[9]

(1, )

[10]

(1, )

[11]

(1, )

[12]	(1, 2, 3, 4, 5, 6, )

[13]	(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, )