[open-cobol-list] Update From AT&T

[Robert Sherry]

We started using OpenCobol over two years ago for several large projects
containing millions of lines of Cobol that had been compiled on MVS with the
IBM Cobol compiler.

During that time we made a number of changes to the compiler to fix bugs,
for MVS conformance, to add extensions, and to improve performance.  We
contributed earlier changes for performance improvements more than a year
ago and they have been integrated into the current compiler release.

At this time we would like to contribute a large number of fixes, additions,
and performance improvements.  We hope that as many as possible will be
merged into the official compiler stream.   We have put #if _ATT_ ...
#endif around most of our changes. In certain cases, it was not practical to
place #if _ATT_ around our changes. These can be removed as the code is
merged into the official compiler source.

Our current compiler maintainer is Bob Sherry and he will add these changes
to CVS unless there are objections.

Here is a summary of the changes we are submitting.

1.      Performance improvements in libcob/numeric.c:
        a.   Performance measurements showed that about 8% of the run time
             was spent with cob_get_sign() and cob_put_sign().  We reduced
             the number of calls to cob_put_sign through the use of macros.
             As a result, changes were made to the file common.h and
             the routine cob_real_put_sign.
        b.   When cob_numeric_cmp() is called with string type arguments,
             in many cases, the comparison can be made without conversion
             to numerical values.  We have added code for this optimization.
        c.   We rewrote decimal_get_packed() and cob_decimal_set_packed()
             using table lookups for much faster performance. These
             routines are defined in numeric.c
        d.   We added a cob_add_int_to_packed() which is an order of
             magnitude faster than having to do the conversions.

2.      Bug fixes:
        a.  RELATIVE_SIZE(f) and  RELATIVE_SEEK(f, i) macros changed to
            work with 64 bit file sizes in libcob/fileio.c.  For
            RELATIVE_SIZE we added a cast to the type off_t. Observe that
            RELATIVE_SIZE calls fseek. In that call to fseek we added a
            cast to off_t in the second argument to the function.
        b.  relative_write(), relative_rewrite(), relative_read_next()
            We modified these routines to work with 64 bit files. Again the
            issue Was the type of the second argument to fseek. These
            routines can be found in libcob/fileio.c
        c.  We changed the output format of the headers in fileio.c to
            big endian rather then in machine dependent format. The Pentium
            is a little endian machine. This was done in the file fileio.c
        d.  Changes related to redefines:
               if f1 and f2 are two fields such that one is a COMP field
               and the other is a POINTER, the COMP field is changed to
               COMP-5 because pointers use native representation.
            This is done in the routine validate_field_1.

3.      Changes to match IBM MVS compiler behavior:
        a.  cob_relax_redefine_value option added to field.c to cause
            redefines with value to be treated as a warning.
        b.  cob_relax_hierachy_levels option added to allow non-group
            levels with different values as if they had the same value.
            This change was made in fields.c and config.def.
        c.  In the previous version, RECORDING MODE IS V was being ignored.
            It now sets the minimum record size to 1 so that it uses
            variable length records.
        d.  We modified redefines to search for the most recent sister
            field with the given name rather than the first field that
            has that name.  This is in field.c.

4.      Language Extensions:
        a.  Partial support for intrinsic functions.
            Intrinsic functions in COBOL use the reserved word FUNCTION.
            The intrinsic functions ABS, CURRENT-DATE, ORD-MAX, ORD-MIN,
            MAX, MIN, and MOD are supported but currently arguments need
            to be fields, not expressions.
            To support intrinsic functions in the compiler, we did the
            following:
            1.  Added the files intrinsics.h and intrinsics.c
            2.  In tree.h, we added a definition for the structure
                cb_intrinsic_call and two macros.
            3.  We modified cobc.c removing the static modifier from the
                routine make_tree.
            4.  The new files stdcoblib.h and stdcoblib.c have been added
                to the runtime library to implement the functions.
            To test functions, we added the file func.at to the directory
            mvs.dir. We updated the file mvs.at to include the file func.at.
        b.  Reserved words can be disabled in config file.
            Under MVS, CYCLE is not a reserved word.  We changed the
            routine cb_init_reserved() in the file reserved.c.  To
            allow such changes to be compiler specific, we added
            "not-reserved" to the file ibm.conf.  We also added the string
            "att?" as a prefix to some keywords in the configuration file.
            We modified config.c to ignore unsupported "prefix?*" config
            options. This allowed us to test _ATT_==1 and _ATT_==0 versions
            of the compiler using a single set of config files.  We expect
            these to be removed for any changes that are merged in to the
            official compiler.

5.      Compiler features:
        a.  New tracing facility.
            The flag -parser-debug was added to the compiler. This causes
            the variable yydebug to be set to 1 which results in the parser
            showing all its shifting and reducing action. This can be
            valuable aid in debugging the compiler but it is not useful for
            debugging COBOL programs.
        b.  Tree dump facility.
            For debugging purposes we added the files dump.c and dump.h.
            The file dump.c contains routines for printing out the
            intermediate representation of the code.  The format is
            suitable for display with GraphViz (using the cob2dot shell
            script, included with our additions.)  GraphViz software can
            be downloaded from http://www.graphviz.org.  The dump.h header
            is included by cobc.c and tree.c
        c.  cb_name() extensions.
            The routine cb_name() was incomplete and we completed it.
            We moved it from tree.c and moved it to a new file name.c.
        d.  Runtime verification of compile options during module
              initialization.
            If module 1 and module 2 were compiled with different versions
            of the OpenCobol compiler and then linked together, the
executable
            might not run properly. Therefore, we now insert run time checks
            for this condition. We added the following fields to the
            cob_module structure:
                unsigned char major
                unsigned char minor
                unsigned char build
                unsigned char patch
            which are checked against the values from the calling module.
            The runtime module checks also check config file
incompatibilities
            between compiled modules.
        e.  We modified the startup to support passing arguments and
            performing initialization at startup.  The compiler option
            -fmain can take the name of a function to call at startup.
            We use this to establish a db2 connection to handle Cobol
            with embedded SQL.

6.      Miscellaneous Changes:
        a.  In fileio.c the line:
               #if HAVE_DB
            Was changed to:
               #if HAVE_DBOPEN.
            This was done due to the fact that some systems have the file
            db.h but do not support the function db_open.
        b.  cob_init - We also added another parameter to cob_init. This
            parameter is called flags and is of type unsigned long. flags
            contain compile-time config flags that must be the same for all
            compilation units; the flags are checked at the same time the
            compiler major/minor numbers are checked.
        c.  In the routine file_open, we removed the local variable fp,
            which was of type FILE *. This was done to stream line the
            code. We changed the output format of the headers in fileio.c
            to be the standard big endian rather then in machine dependent
            format. The Pentium is a little endian machine.

7.      Build Changes:
        a.  We have added an nmake Makefile that can be used to build and
            package the compiler using the AST Toolkit which can be
            downloaded from http://www.research.att.com/sw/download.
        b.  The file config.iffe is included.  When building with nmake,
            this file is used by the iffe command to generate the config
            header file.