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ASE2 CARD CATALOG ENTRY |
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ASE2 CARD CATALOG ENTRY |
Instructions:
This is the second release of this translator. It my hope that it soon will be provided in source form free of charge.
The C programming language enjoys an enormous amount of popularity thanks to its free distribution with the Unix operating systems and to its early acceptance among the accedemic community. That being the case there is a large amount of useful software, libraries and algorithms that are freely available to C programmers. I'd like to provide a means of making that software base easily accessible to the Ada community as well.
This translator generates some types that are not immediately portable to all Ada compilers. However, most of the generated types are subtypes from the package C provided in this distribution. The very first thing you will need to do before the generated Ada code will compile is retarget package C to your compiler. Don't worry about getting all the unsigneds correct before you start playing with the translator, just make sure the sizes of the types are correct. You'll be able to lookup all the nasty compiler hacks at a later time.
This version of the translator is basically a parser for the ansi C type system. It also includes a built in C preprocessor that attempts to make macro definitions available to the Ada community as well. A major ATTEMPT was made to maintain the exact names from the original C source. This is not always possible.
I prefer a loose type system so most types generated by the translator will follow that philosophy. It feels like the "right thing" to do when the language you are interfacing to is so relaxed. I'm quite sure this will be a point of contention to many in the Ada community. There already appears to me to be two factions; those who derive everything and those who are forced to cast cast cast cast cast :-). Anyway, back to the particulars. Unions, unsigneds and function pointers are not supported by all Ada compilers. The code generated by this translator targets the ICC Ada compiler and will be particular to it in this release (like I said I'd like to make the sources available for others to port to verdix, dec, mips, rational ...).
Unions are implemented as records whose fields are overlayed via rep specs. The overlaying of fields via rep specs is not allowed in the Ada language. However, most compilers realize that it is a very useful thing to do and will have some mechanism that supports it. I have already received and rejected feedback from some who'd like to see this become some sucky variant record. Sorry to those of you who hold that opinion but a C union is not an Ada variant record.
union u1 {
int field1;
char *field2;
};
type u1 is
record
field1: int;
field2: char_p;
end record;
for u1 use
record
field1 at 0 range 0 .. 31;
field2 at 0 range 0 .. 31;
end record;
Unsigned integers are supported by most compilers through some mechanism or another. They are generated by this translator as subtypes to a type from the package C. Once you get the package C ported properly unsigned integers should work just fine.
Function pointers are subtypes of system.address and loose their prototype information (parameters and return type). This is unfortunate, but I haven't yet thought of a good way around it. I'm open to any and all suggestions. Type aliasing:
C has a very forgiving type system. This translator attempts to model that behavior. I have gotten some good feedback here about generating derived types from typedefs and will be incorporating that into the next release. Anonymous types:
One important thing that I'd like to mention here in defense of the current implementation is that user type names are preferred over generated type names. For example:
extern char *p1;
struct s {
char *p2;
};
typedef char *caddr_t;
type s;
type caddr_t is access char;
type s is
record
p2: caddr_t;
end record;
p1: caddr_t;
pragma interface(c, p1);
I have received negative feedback from many who don't like the fact that variables with anonymous types (as in p1 and p2) will have their types promoted to another type. The reason this is done is to avoid compiler generated type names. In the above example the compiler could have generated some type name for the anonymous char * types of p1 and p2. This was not done because the user provided a type name with a base type of char *. My contention with compiler generated type names is that if I use them you will have to go searching through the output to find the names the translator chose. If instead you provide a low level typedef scheme of your own, you can be assured that the translator will choose your names, which I think is a more deterministic approach.
As this is only released in binary format at the moment we have compiled it on all of the major platforms that people have asked for, and bundled all of the support files into a single tar file per platform. The currently supported platforms are:
Sun sparc at SunOS 4.0.2 Sun motorola at SunOS 4.0.2 Sun Intel at SunOS 4.0.1 Mips R3000 at RISC/os 4.52 Mips R3000 at SGI Irix 4.0.5 Mips R3000 at DEC Ultrix 4.2 IBM RIOS at AIX 3.1 HP700 at HP/UX ???? HP835 at HP/UX ????
Please contact Mark Schimmel (mark@irvine.com) with coding bugs or feature requests, and John Schimmel (jes@sgi.com) with release problems.
21 Jan 94 1.0.2 Mark Schimmel Release to the PAL
This prologue must be included in all copies of this software. Restrictions on use or distribution: NONE Everyone is permitted to copy and distribute verbatim copies of this software as long as this document is distributed with it, but changing it is not allowed. All rights to this C header file to Ada source translator are reseverved by Irvine Compiler Corporation. It has been provided free of charge without support and without any obligation on the part of Irvine Compiler. THIS SOFTWARE IS PROVIDED "AS IS" WITH NO WARRANTIES OF ANY KIND INCLUDING THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. In no event will Silicon Graphics, Inc. be liable for any lost revenue or profits or other special, indirect and consequential damages, even if Silicon Graphics, Inc. has been advised of the possibility of such damages.
This software and its documentation are provided "AS IS" and without any expressed or implied warranties whatsoever. No warranties as to performance, merchantability, or fitness for a particular purpose exist. The user is advised to test the software thoroughly before relying on it. The user must assume the entire risk and liability of using this software. In no event shall any person or organization of people be held responsible for any direct, indirect, consequential or inconsequential damages or lost profits.
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