Production Quality Ada Compiler Criteria

[hogan@AEROSPACE.ARPA]

I am writing a standard for procuring an Ada compiler and would
like to check some numbers against the Ada community.  
I would appreciate hearing most from Ada implementor but also 
knowledgeable systems programmer types who have used Ada to build
some moderately sized (~5000 lines) Ada programs.  I got the numbers
from examining what a few of the validated Ada compilers provide and
using my own judgement, but I need your input so we don't publish a 
standard that no compiler can or will ever meet.

The following requirements are indended as minimal requirements that
any Ada compiler must meet to be judged as production quality.  
(note the (M) means mandatory and the (A) means the requirement may be
mandatory depending on the user's application).  It may be that a very
good compiler will meet most of these  requirements and only fail on a
few.  We have not yet attached a weighting factor to the requirements.

2.1.1    (M)  A compiler shall compile the ACVC and ACEC test suites with at 
              an average rate of at least 250 Ada source statements per minute 
              (elapsed time), for each 1 MIPS of rated processing speed of the 
              specified host computer. 

2.1.2    (M)  A compiler shall compile the ACVC and ACEC test suites with at 
              an average rate of 100 Ada source statements per minute (elapsed 
              time), for each 1 MIPS of rated processing speed of the 
              specified host computer, while meeting the object code 
              requirements.

2.2.1    (M)  The compiler shall produce an object code program that requires 
              no more than 15% additional target computer memory space than an 
              equivalent program written in assembly language.

2.2.2    (M)  The compiler shall produce an object code program that requires 
              no more than 5% additional execution time than an equivalent 
              program written in assembly language.


                                   Capacity

The following are minimal capacity values, i.e. a compiler can allow more
than 1000 compilation units in a program but it must allow at least that
number.

Item                       			    allowed size

compilation units					1000
source lines/ compilation unit				10,000
characters/ source line					80
identifiers/compilation unit			source lines = 10,000
library units in a context clause		compilation units = 1000
Levels of nesting in a program unit		 	16
Declarations in a compilation unit		number of identifiers=10000
Formal parameters in an entry or subprogram		64
Frames an exception may be propagated through		256
Exceptions & handlers in a program unit/frame		256
Number of bits in any object				MAX_INT
Number of characters in a STRING object			50,000
Enumeration literals in a type				256
Dimensions in an array					16
Elements in an array (all dimensions)			MAX_INT
Discriminants in a record				64

				Ada-Related

The following requirements are specifically related to implementation
 of certain Ada constructs.  I would appreciate comments about their
appropriateness and content.

5.1.1    (M)  The compiler shall eliminate statements or subprograms that will 
              never be executed (dead code) because their execution depends on 
              a condition known to be false at compilation time.

5.2.1    (M)  In addition to the basic 60-character set, a compiler shall 
              allow any of the 26 lower case letters in identifiers and both 
              the 26 lower case letters and 13 other special characters in 
              specified in LRM paragraph 2.1 in character strings and comments 
              to the extent that the underlying host computer supports them.

5.2.2    (A)  A compiler that provides the predefined package TEXT_IO shall 
              permit input and output data to contain any of the 95 graphic 
              characters or 5 form effectors of the ISO seven-bit character 
              set (ISO Standard 646) to the extent supported by the target 

5.3.1    (M)  The compiler shall provide predefined types for all the integer 
              and floating-point types provided by the target computer.

5.3.2    (M)  The attribute 'MACHINE_OVERFLOWS shall be TRUE for all 
              floating-point and fixed-point types.

5.3.3    (M)  The compiler shall implement enumeration types using an 
              underlying type that requires the least amount of memory to 
              represent that type.

5.3.4    (M)  The range of enumeration code values allowed in an enumeration 
              representation clause shall be MIN_INT to MAX_INT.

5.3.5    (A)  The compiler shall support length clauses, enumeration 
              representation clauses, and record representation clauses,
	      and address clauses.

5.3.7    (M)  The attributes T'SIZE for discrete types and T'SMALL for 
              fixed-point types shall be implemented.

5.3.8    (M)  The components of records types and array types named in a 
              pragma PACK shall be stored in contiguous memory bits.

5.5.1    (A)  The compiler shall provide at least 8 priority levels for 
              specifying tasking priorities via the pragma PRIORITY.

5.5.2    (A)  The pragma SHARED or an equivalent capability shall be provided.

5.5.3    (M)  A mechanism for termination of tasks that depend on library 
              packages shall be provided.

5.5.4    (M)  The compiler shall provide a capability for handling target 
              computer hardware or operating system interrupts as calls to Ada 
              task entries.

5.5.5    (A)  The resources to create, interrupt, terminate, fail and abort a 
              task shall be no more than those required to call and return 
              from a subprogram.

5.5.6    (M)  The ordering of select alternatives in a selective wait 
              statement shall not impact overall execution speed of the 
              program.

5.5.7    (M)  The compiler shall dispatch the execution of ready tasks in a 
              manner that will give each task an equal share of the processing 
              resources.

5.5.8    (M)  Tasks that are blocked, completed, terminated, or not activated 
              shall not impact the performance of the remaining code.

5.5.9    (A)  The value of DURATION'DELTA shall not be greater than 1 
              millisecond.

5.5.10   (M)  The basic clock period, TICK, as defined in package SYSTEM shall 
              be the smallest time increment supported by the target computer 
              hardware.

5.6.1    (M)  An exception shall not impact execution speed unless it
	      raised.

5.6.2    (M)  The compiler shall provide the pragma SUPPRESS or 
	      an equivalent capability to permit suppression of 
              the execution of the pre-defined run-time checks for a 
              designated compilation unit.

5.6.3    (M)  The compiler shall issue a warning message for violation of a 
              constraint exception which is always raised at run-time.

5.7.1    (A)  The compiler shall maximize code sharing between multiple 
              instantiations of generic units.

5.8.1    (M)  The compiler shall provide the pragma INTERFACE to allow 
              importing programs written in the assembly language of the 
              target computer.

5.8.2    (A)  The compiler shall provide the pragma INTERFACE, or an 
              equivalent mechanism, to allow incorporation of object modules 
              compiled from other languages.

5.9.1    (M)  The generic library subprograms UNCHECKED_DEALLOCATION and 
              UNCHECKED_CONVERSION shall be implemented with no restrictions 
              except that the target type of UNCHECKED_CONVERSION may exclude 
              unconstrained types.

5.10.1   (A)  An implementation shall provide support for format directed 
              input/output for each target computer that supports text 
              input/output.

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Responses via electronic or conventional mail are OK.  I would like to
have them as soon as possible.

Michael Hogan
Aerospace Corp.  M1/106
POB 92957
Los Angeles, CA 90009
(213) 615-4346