Splint - Secure Programming Lint
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Changes from Checks Mode 2Differences
Fixed errors reported in second iteration.
Now, running LCLint in checks mode detects no anomalies.
- employee - employee datatype (LCL, Code, Header)
- empset - sets of employees (LCL, Code, Header)
- dbase - database of employees (LCL, Code, Header)
- eref - reference to an employee (LCL, Code, Header)
- erc - collection of erefs (LCL, Code, Header)
- ereftab - table of employees and erefs (LCL, Code, Header)
Naming ConventionsNow we check that the code conforms to a naming convention. There is no defined naming convention, so we will make one up that is close to what the code already (almost) follows.
Czech NamesThe code most closely fits the Czech naming convention, where identifiers are preceded by the associated type name followed by and underscore. We use the +czech flag to select the Czech naming convention. LCLint reports 10 anomalies. The first message reports a constant that does not follow the Czech naming convention:eref.lcl:7,15: Constant erefNIL name is not consistent with Czech naming convention. The name should begin with eref_ Constant name is not consistent with Czech naming convention. Use -czechconsts to suppress message.In fact, it follows the Slovak convention (
). We could use the +slovakconstants flag to require that constants follow the Slovak instead of the Czech naming convention. Instead, we change the name to eref_undefined. After changing the declaration, we can run lclint using +repeatunrecog to find all the places where erefNIL appears and replace them with eref_undefined. (Of course, if this were a larger system we would want to use emacs tags and M-x tags-query-replace to do this more efficiently.) The next six messages report function names that are inconsistent with the Czech naming convention:< reading spec dbase.lcl > dbase.lcl:17: Function hire name is not consistent with Czech naming convention. Accessible types: db Function or iterator name is not consistent with Czech naming convention. Use -czechfcns to suppress message. dbase.lcl:32: Function uncheckedHire name is not consistent with Czech naming convention. Accessible types: db dbase.lcl:41: Function fire name is not consistent with Czech naming convention. Accessible types: db dbase.lcl:49: Function query name is not consistent with Czech naming convention. Accessible types: db dbase.lcl:57: Function promote name is not consistent with Czech naming convention. Accessible types: db dbase.lcl:68: Function setSalary name is not consistent with Czech naming convention. Accessible types: dbThe names are in the dbase module where the only accessible type is the specification-only type db. We add db_ in front of the names.
The other message is for check, which was added to bool.h:bool.h:34,29: Function check name is not consistent with Czech naming convention. Accessible types: boolThe check macro really does not belong in the bool module. In a real program, we would add a separate utilities file. Here, we add a /*@noaccess@*/ comment before check is declared. Since there are no accessible types now, check is a valid function name.
The final two messages report type names that are inconsistent with the Czech naming convention:eref.h:9,30: Datatype eref_status name violates Czech naming convention. Czech datatype names should not use the _ charater. Type name is not consistent with Czech naming convention. Czech type names must not use the underscore character. Use -czechtypes to suppress message. eref.h:14,3: Datatype eref_ERP name violates Czech naming convention. Czech datatype names should not use the _ charater.Since the Czech prefix is distinguished by the underscore character, names of types cannot use the underscore character. The types are renamed erefStatus and erefTable.
Distinct NamesLCLint can detect names that are not sufficiently different from other names in the program. This can be necessary to check portabilty to old compilers that only use the first n characters of an identifier. It is also useful for the programmer, to reduce the possiblity of using the wrong names. Running LCLint using +distinctexternalnames produces 34 messages. The default number of significant characters in an external name is 6, and alphabetic case is not significant in comparisons. (This is the minimum that is acceptable in an ANSI conforming compiler.)
If we were really determined to have a program that is portable to old systems, we should change these names to be different in the first six characters. (We would probably have to abandon the Czech naming convention to do this.) Instead, we use -externalnamelength n to find the minimum number of characters used in comparisons. We can try different values to see how many errors are reported. With -externalnamelength 12, 2 errors are reported. With -externamelength 14, no errors are reported.
We haven't made the program any more portable, but at least this is clearly documented now. Someone trying to compile the program in an environment where less than 14 characters are used for external names, will need to edit the source code first.
Internal names can be checked similarly, except the default length is 31 characters. We can use +internalnamelookalike to check that names do not look the same (e.g., differ only in lookalike characters like 1 and l. Checking reports no errors.
Namespace PrefixesThe Czech naming convention prescribes prefixes for names associated with abstract types. We can use specific namespace prefixes to restrict other names, and place more restrictions on the abstract type names.
One common convention is that names of expanded macros should use all uppercase letters. This is expressed by -uncheckedmacroprefix "^~*". That is, an uppercase letter followed by one or more non-lowercase letters. Macros that implement functions or constants and are checked by LCLint do not have to match the uncheckedmacroprefix, since clients should not need to be aware that the implementation is a macro. One message reports a violation of this convention:Since employeeFormat is preceeded by /*@notfunction@*/ it is expanded normally, and is in the unchecked macro namespace. We initially rename it to EMPLOYEEFORMAT. This produces one new message:employee.h:8: Name EMPLOYEEFORMAT is reserved for future ANSI library extensions. Macros beginning with E and a digit or uppercase letter may be added toNames beginning with E may be reserved for the ANSI library, so we should use a different name. It is changed to FORMATEMPLOYEE.
. (See ANSI, Section 4.13.1) External name is reserved for system in ANSI standard. Use -ansireserved to suppress message.
We might want to use a similar convention for enumerator members. We add -enumprefix "^^~*". This means an enumerator must start with two capital letters, and the rest must be all non-lowercase letters. Fourteen messages report violations of the enum prefix. We fix these by changing the names to use all capitals.
Initialization FileNow, we move the name convention flags into an .lclintrc file. The .lclintrc file in the current directory is read before checking begins. If we wanted this naming convention to apply to code in other directories too, we would put the flags in the .lclintrc file in our home directory.
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