Impact of suppressing some compiler diagnostics

[John E. Malmberg]

As these messages are being suppressed in last release of SAMBA 2.2.8, 
it is probably useful to indicate what the impacts of suppressing them are.

With a program as complex as SAMBA, if any of these are causing a 
problem, it may be difficult to notice in all cases.

I am still trying to get all the changes done that will allow SAMBA 
2.2.8 to compile and run on OpenVMS 8.2 with out most of these messages 
suppressed.

The questcompare1 messages are showing definite bugs that so far have
not been traced to any issues I have seen posted on the SAMBA_VMS
mailing list.

-John
wb8tyw at qsl.network
Personal Opinion Only


CVTDIFTYPES

     This indicates a data conversion is being requested that
     is not defined according to standard C.  While the HP C
     compiler will usually guess right on the conversion, this
     code is not portable, nor can it be guaranteed that the
     conversion will be correct.

     As it is a non-standard conversion, any changes in the
     code or build environment can change the result.

     Usually this means a programming error.

     Many times it means a missing cast, but other times
     it means that a variable is defined differently than
     what it is used for.

     This message should almost never need to be suppressed.


DUPEXTERN

     This means that two externally visible symbols have the
     same name. This should never happen and is an indication
     of a programming error.


EXPRNOTUSED

     This indicates that an expression is not used.  It's presence
     usually indicates a programming error.  The most common is
     that a "==" was used instead of an assignment.

     It sometimes means that a macro to inhibit some function
     was not coded in a way that would not cause the message.

     This is a high indication of a bug.


IMPLICITFUNC

     The compiler does not have a definition for this function,
     and is falling back on the old C definition of the function.

     It is a violation of the C standard for any function that
     takes a variable number of parameters to be implicitly
     defined.  And on several platforms, the C compiler will
     generate the wrong code for such functions if it does
     not detect the error.

     All known versions of HP C on VMS will always generate
     the correct code in this case for the varying number of
     calling parameters, but the prefix for the external
     function may be incorrect for options of the the module
     being compiled.

     This should be considered a bug as it should be trivial
     to correct.


INPTRTYPE

     This is a detected illegal type conversion.  Data corruption
     is possible.  High probability of a programming error.

     Many times it means a missing cast, but other times it
     means that a variable is defined.

     This message should never need to be suppressed.


INTCONCASTTRU

     This means that the program is trying to put a constant
     value into a data cell that is too small and trying to
     use a cast to do a type conversion.

     High probability of a programming error.

     This usually indicates that a variable is declared
     differently than it is actually used, or a mask is
     missing to manually truncate the significant bits of
     the data is missing.

     This message should almost never need to be suppressed.


INTCONSTTRUNC

     This means that the program is trying to put a constant
     value into a data cell that is too small for it.

     High probability of a programming error.

     This usually indicates that a variable is declared
     differently than it is actually used, or a mask is
     to manually truncate the significant bits of the data
     is missing.

     This message should almost never need to be suppressed.


MACROREDEF

     A macro is being unexpectedly reassigned.  This can be
     by design, or can indicate a programming error, usually
     indicating an inconsistency in the order that header
     files are included.

     I usually find this to be from a programming error where
     the wrong macro definition is being used in some parts of
     a program.

     As this problem can usually be easily fixed, this
     message should rarely need to be suppressed.


MIXLINKAGE

     A symbol is declared as both internal and external in
     the same scope.  That means that the compiler can not
     know what to do, and is guessing.  It can not be
     predicted if the HP or any other compiler is doing the
     right thing.

     This is usually a programming error.

     This message should never need to be suppressed.


NESTEDCOMMENT

     This usually indicates that a section of code is
     accidentally being commented out.

     In the case of SAMBA 2.2.8, there is one case that
     there is a minor bug in the SMG$ header files.  I
     will be filing a bug report for that to be fixed in
     a future release.

     For user written code it is probably better to fix
     the code than to suppress this message and risk an
     unterminated comment affecting a large block of code.


NOTCONSTQUAL

     This indicates that you are potentially allowing the
     modification of data that the compiler has been told
     is not supposed to be modified.

     Suppression of this message can result in data corruption
     and improper operation of the program.

     The big risk is that a module that calls a module that
     is displaying this diagnostic will be assuming that the
     data was not modified.  And is not likely to always use
     the modified data.

     About the only place a cast is legitimately needed to
     to suppress this message is when a (const * char) needs
     to be assigned to a dsc$a_pointer, and a pointer to that
     structure will be passed to a VMS routine as a read only
     parameter.

     All other occurrences should be examined carefully as they
     are likely a critical bug.


PROTOSCOPE

     There is an error in a function prototype where it is
     referencing a type that has not yet been defined.

     This indicates a bug in the header definitions, or
     the order that header files are defined.

     The HP C Compiler on VMS will still generate the correct
     code.

     On other platorms the C compiler will not have the
     the information needed to generate the correct code.

     This bug should always be trivial to fix, so this message
     should never need being suppressed.


RIGHTSHIFTOVR

     The compiler has detected that the resulting expression
     is going to always result in 0 for an unsigned result, or
     0 or 1 for a signed result.

     This usually is the result of a programming error.

     This message should almost never need being suppressed.


NONSTANDCAST

     The cast used to assign a symbol to a function pointer is
     illegal.  HP C on VMS will do the expected thing here.

     Such code is not portable, and is present in the UNIX
     SAMBA code.

     Suppressing this message is a quick way to get the
     compile done, but this really is an indication of a bug.

     I have not yet determined the way to recode these
     sections of SAMBA to be compliant with the C standard.


NOPARMLIST

     Declaring a prototype or a function with no parameters
     is now strongly discouraged.

     Declaring a prototype this way for a function with
     a varying number of parameters is illegal by the
     C standard.

     The HP C compiler on VMS will generate the expected
     code.  Other C compilers on other platforms will not
     when the function has a varying number of parameters.

     As this is trivial to fix, this message should never
     need to be suppressed.


OUTTYPELEN

     An illegal output conversion has been requested and
     detected at compile time.  The resulting data may
     be formatted incorrectly.

     This is usually a programming error.

     This message should almost never need to be suppressed.


PTRMISMATCH

     An incompatable pointer conversion is being requested.

     This usually indicates a minor programming error,
     usually in a function prototype where a data type is
     being declared in a mannor contray to it's use.

     This message should almost never need to be suppressed.


PTRMISMATCH1

     An incompatable pointer conversion is being requested,
     where the mismatch is between a signed and unsigned
     data type.

     This usually indicates a programming error that can
     result incorrect program operation with comparison
     operations.  Usually a prototype or variable is
     not declared according to it's use.

     This message should almost never need to be suppressed.


QUESTCOMPARE1

     This indicates that an unsigned value is being tested
     to see if it is less than zero.  This of course can
     never happen.

     This indicates a programming bug.

     Several occurrences of this are found in what appears
     to be the UNIX code base, mostly involving the time_t
     data type.  It needs to be verified if this bug is
     present in the current UNIX releases and the proper
     BUGZILLA reports filed.

     The impact of these compiler detected bugs is still
     unknown.  The compiler is clearly not generating the
     intended code in almost all of the cases discovered
     so far.

     Suppressing this message will usually leave serious
     programming bugs undetected.