May 2016 - I was looking through my small collection of VAX Professional magazines and decided to take another look at this unpublished article, which is probably my favorite of the articles I've written. I have the year, 1990, at the bottom of this page, so I assume I had a good reason for choosing that date when I made this web page maybe 20 years ago.
My vague memory of the article submission process was that I wrote the article and submitted it to VAX Professional. I must have received a letter from them accepting the article for publication, followed shortly after by another letter saying they had changed their minds. I was then contacted a third time with a request that I enhance the program to read VMS object libraries as well as regular object files. I did this and resubmitted the article and code in the form you see below. A fourth letter must have conveyed the final rejection. Bummer!
On December 31, 1981, I went to work for General Electric's Space Division, who was building the satellite control center and image processing systems for LANDSATs 4 and 5; I worked on the image processing side. As I mention in the article, we software developers had to hand-draw structure charts for our design documents and update them after the programs were finished. Early on in 1982, my team leader's supervisor, Duane Jarc, once spoke to Diane Mularz and me about some thoughts he had been mulling over regarding alternative methods of representing structure charts, representations that would be easier to update. He was a former math major and he talked about lattices, but we never latched onto anything concrete.
More than a year later, probably late 1983, I wrote the first version
of STRUCHART. It scanned the
.LIS files output by the
FORTRAN compiler, constructed a call graph for the program(s), and
printed out a textual structure chart. A colleague also found the
program useful and recommended me for a $10,000 Cost Improvement
Award, which was approved in 1984. (In his recommendation, he
calculated the savings to the company as $10,000. For that, I
probably got $10 and a certificate!)
Beginning in Fall 1984, I worked for about a year on an embedded 80286 project on which we used Intel's PL/M-86 language. I describe in the article how I was able to hack the PL/M-86 source code into STRUCHART intermediate files and generate a structure chart for my code. Then, in late 1985, I returned to VAX/VMS development and, at that time, I must have added the capability to read and extract calling information from VMS object files. Aside from their usefulness to my program, I was fascinated by VMS object files. My 30-year-old memories of reading the VAX/VMS Linker manual are of me learning that object files were literally programs written in a postfix, stack-based language that, when interpreted by the Linker, specified how to construct the executable. Wow!
In 1987, our GE facility began closing down. (Several years earlier,
the military side of the Space Division was caught doing some creative
bookkeeping and the entire division, including the civilian side, was
banned from bidding on government contracts. Bye-bye, NASA! We
finished up a commercial contract and closed up shop.) In September,
I left GE with a 9-track tape containing my VMS programs under my arm
and was recruited by a small company, Integral Systems. I joined
a project that was building a distributed satellite control center
based on Sun workstations for NASA. The company's NOAA project had
Data General computers with 9-track drives, so I was able to retrieve
my stuff off my GE tapes. Consequently, I have the last version of
STRUCHART from my GE days; the program could still read both
.LIS files (even generating the listings on-the-fly
by invoking the FORTRAN compiler with
.OBJ files. The STRUCHART source files are dated
October 1988, which would have been when I transferred them off
the tape and, by hook and by crook, managed to get them over to
our Sun workstation. I describe in the article how I ported the
program to UNIX and used its intermediate file capabilities in
Now here is where I become puzzled. In looking through my copies of
VAX Professional in May 2016, I came across an article
by Darren C. Abbott, "HIERARCHY: A Procedure to Generate a Call
Hierarchy" (VAX Professional, April 1989). Darren's
program generated, for each module A in the target code, a list of
modules that call A and a list of modules called by A. Like my
later version of STRUCHART, HIERARCHY scanned
for symbol information. Our programs differed in that his program
used the Module Header (MHD) and Global Symbol Definition (GSD)
object records, whereas mine used the MHD and Text Information and
Relocation (TIR) records.
I'm guessing that Darren's article probably inspired me to write my
article. The similarity of our programs would have been a good reason
for VAX Professional to reject my article. What I don't
understand is why I didn't reference Darren's article in mine. In my
other articles, I reference earlier, related articles, so it was not
like me to not reference HIERARCHY. Furthermore, my practice
under VMS (both in FORTRAN and later in C with UNIX-style command-line
options) has always been to declare a program as a foreign command,
LIB$GET_FOREIGN() to get the command line, and then
parse the command line myself. The STRUCHART I took away from GE was
written in this fashion. However, the version of STRUCHART in my
article uses the VMS Command Definition Utility (CDU) in a manner
almost identical to Darren's use of CDU, down to the "/[NO]DOLLARS"
option! All in all, I owe a big acknowledgement to Darren Abbott,
whose article inspired me to write this article and showed me ways
to provide a more professional version of STRUCHART.
In 1992, I returned to VAX/VMS to port our UNIX workstation-based satellite control center to VAX/VMS workstations. Aside from recompiling STRUCHART, I also wrote a C version, oflow (a name derived from UNIX's cflow(1) program). I had hoped to eventually extend it to UNIX object files (in whatever format), but I never followed through on that idea. Like Darren Abbott, I found that using VMS object files for generating call graphs worked fairly well for restricted, but common, structuring of FORTRAN files, but not very well when applied to other languages' object files.
In the 1990s or the early 2000s, I wrote an uncommented program,
gflow, which can be used
in situations where I formerly used STRUCHART's intermediate file
capability. The program's input is a series of lines, each line
specifying the vertices at either end of an arc in a directed graph.
For example, "main init" could represent the arc in a call graph
that indicates that
csoft archives found
here include the
source code for the program and the needed library.
Source Code: struchart.zip is a ZIP file of the source files. These are all UNIX (LF-terminated) text files. It's been about 10 years since I've used ZIP on VAX/VMS, so you might need to do "unzip -a" to convert the files to VMS text files. I also read somewhere that object file records are slightly different on Alpha systems, not to mention that they might have changed considerably since the 20-year-old versions of VMS that I last used.
Early in my programming career, I spent many a tedious hour, with a pencil and eraser in one hand and a flowchart ruler in the other, drawing structure charts. Drawing a structure chart, which shows the calling hierarchy of a program, was not a one-shot effort; it had to be done before and after the internal design review, before and after the external review, and finally, updated to "as built" prior to turning the software over to the customer.
Since a typical program consisted of 50 to 100 or more modules and its structure chart spanned 5 to 10 pages, updating a structure chart was always put off as long as you could get away with it. Not being particularly adept at drawing any type of diagram, I cast around for an easier way to document the structure of my programs. The result was STRUCHART, a tool that automatically constructs the calling tree for a program.
STRUCHART reads the VAX/VMS object modules making up a program (or multiple programs), extracts the global symbols defined in each object module, and builds the structure chart(s) defined by that symbol information. The structure chart is a textual structure chart, where indentation is used to represent the relationships between modules. For example, the graphical structure chart shown in Figure 1 would appear as follows in textual form:
MAIN INITIALIZE PROCESS GET_DATA TRANSFORM_DATA PUT_DATA TERMINATE
The STRUCHART program is compiled and linked using a DCL command procedure,
BUILDSC.COM (not shown):
After building the executable, you must then add STRUCHART to your process
command table using the VMS Command Definition Utility (CDU). This is
conveniently done in your
$ SET COMMAND STRUCHART.CLD
STRUCHART.CLD is the
Command Language Definition file for the structure chart generator.
To make it more readily available to all users, your system manager
can add STRUCHART to the system-wide DCL command table:
$ SET COMMAND/TABLE=SYS$LIBRARY:DCLTABLES /OUTPUT=SYS$LIBRARY:DCLTABLES STRUCHART.CLD
Once entered into a command table, STRUCHART is invoked by:
$ STRUCHART [/[NO]DOLLARS] [/MAIN=(name[,...])] [/OUTPUT[=output_file]] [input_file_spec[,...]]
/[NO]DOLLARS option controls the inclusion of module names
with embedded dollar signs (generally indicative of system routines).
NODOLLARS excludes all module names with embedded dollar signs;
DOLLARS includes all module names with embedded dollar signs.
If neither is specified, STRUCHART excludes names according to its default
list of module name prefixes (
Normally, STRUCHART prints out a structure chart for each module which is
not called by any other, i.e., the module is the main routine of a program.
/MAIN option is used, STRUCHART only prints out structure
charts whose roots are the specified module names.
STRUCHART's default output device is your terminal (
/OUTPUT=output_file on the command line
redirects STRUCHART's output to a file. Specifying
without a file name causes STRUCHART to create a new output file,
module.SCO, for each struchart chart generated, where
module assumes the name of the main module in each structure chart.
Each input_file_spec can be a single file or a wildcard file
specification; wildcards are expanded into the matching set of files.
STRUCHART handles three types of input file: object files, object
libraries, and intermediate files. Object files are the standard
.OBJ files generated by VMS compilers and assemblers.
Object libraries (
.OLB files) collect object modules
from multiple object files into a single library file; these object
modules are scanned and treated as if separate object files were specified.
STRUCHART intermediate files (
.SCI files) are read as text
files containing module calling relations. All other input file names
have their file extension replaced by
.OBJ; e.g., you can
*.FOR and STRUCHART will pick up the corresponding
.OBJ object files.
As an example, suppose you're in the STRUCHART directory. The following
command builds the structure chart for STRUCHART and writes it to
$ STRUCHART/OUTPUT *.OBJ
"Sticky defaults" are applied to input file specifications, so
$ STRUCHART *.FOR,ALEX$LIB:*.OLB,*.OBJ
reads, in succession, FORTRAN-generated object files in your current
.OLB object libraries in
.OBJ files in
STRUCHART is composed of 12 modules: a main program and 11 subprograms.
The main program parses the command line
arguments and calls the other functions. The complete source code
(struchart.zip) for STRUCHART can be
downloaded from ARIS (obsolete); two subroutines of interest,
DFS_PRINT, are described and
The original STRUCHART, written under VMS version 2.5, scanned FORTRAN
compiler listings (
.LIS files) for the information needed
to build a call tree. Two passes were made over each list file. The
first pass located the
Functions and Subroutines Referenced
section found near the end of a listing and extracted the routine names
from that section. The second pass tried to sort the names into their
order of reference within the program text. As you can imagine, the code
to accomplish all this was not a pretty sight. Major revisions were
required whenever a new compiler release introduced drastic changes into
the list file format.
Surprisingly, reading list files was not unduly slow; the time-consuming aspect of generating structure charts in this manner was recompiling all the modules to produce the list files, which, to conserve disk space, were normally not kept around. The major disadvantage of the original STRUCHART was not its speed, but that it was limited to FORTRAN programs.
Several years and several versions of VMS after writing the first STRUCHART,
I happened upon the description of object files in the VAX/VMS V4.3 Linker
manual. A light flashed on in my mind and, following examination of some
real object files, I updated STRUCHART to read
.LIS files. Since the formats of object modules
in object files and object libraries are identical, the capability of
reading object libraries was easily added in a later upgrade of STRUCHART.
READ_OLB read object
module records from object files and object libraries, respectively. Each
record is passed to
processing. When a module header record is input,
extracts and saves the module name. When a Text Information and Relocation
(TIR) record is read, each global symbol is extracted and a
module-calls-symbol relation is stored in STRUCHART's internal
data structures. References to low-level system routines (e.g.,
OTS$xxx, etc.) are discarded at this point.
The contents of the TIR records are essentially a tokenized instruction
stream that the Linker reads and interprets to build an executable image.
DATA_LENGTH table in
GET_SYMBOLS how to increment
its "program counter" through the instructions in a record. TIR records
were chosen over the Global Symbol Definition (GSD) records as the source
of external references since the symbols' order of occurrence in the TIR
records more closely approximates the order of their occurrence in the
Since our VAX had a limited number of languages available, STRUCHART was
tested primarily on FORTRAN and MACRO object modules. Some Pascal software
supplied by another company was also subjected to STRUCHART, but the results
were not examined closely. STRUCHART's module-based tree derivation can
cause problems with object files generated by other compilers. C language
object files, for instance, contain a single module per file: the module's
name is the name of the source file and the functions defined in the source
file are treated as entry points within that one object module. Therefore,
if you restrict yourself to one function per source file, STRUCHART should
prove useful with C language object files, too. Running STRUCHART on an
Ada library (and
ANALYZE/OBJECT on an object file extracted
from the library) produced no useful information.
Earlier versions of STRUCHART made use of a scratch disk file to store intermediate results. As the object files were scanned, the intermediate file accumulated information about what routines directly call what routines. STRUCHART then read the intermediate file, built the calling hierarchy, and generated the structure chart. Later versions of STRUCHART eliminated the need for an intermediate file, but the ability to read these files was retained since the files are useful in their own right (see the discussion of STRUCHART applications further on).
STRUCHART intermediate files are normal VMS text files; the intermediate file for the example program given in Figure 1 might look as follows:
Routine GET_DATA Calls Routine INITIALIZE Calls Routine MAIN Calls INITIALIZE PROCESS TERMINATE Routine PROCESS Calls GET_DATA TRANSFORM_DATA PUT_DATA Routine PUT_DATA Calls Routine TERMINATE Calls Routine TRANSFORM_DATA Calls
The calling information extracted from STRUCHART's input files is used to
build a directed graph of the target program's structure. The fact that
A calls routine
B in the program is
represented in the graph by two vertices,
connected by an edge from
B. Recursion and
utility functions called by multiple routines prevent us from using strict
The call graph, constructed as the input files are read, is represented
using adjacency lists. A routine table contains the names of all the
modules in the program. Attached to each routine X in the table
are two adjacency lists: a list of those routines that X calls
CALLS array) and a list of those routines by whom
X is called (the
CALLED_BY array). Figure 2
shows the graph constructed for the example program in Figure 1.
After the graph is built, STRUCHART steps through each name in the routine
table. If an entry in the table has an empty
(i.e., no other routines call this one), the routine is assumed to be the
main module of a program and the root of a call tree; therefore, a structure
chart for it is generated. STRUCHART keeps track of where each routine is
defined, so that unreferenced library routines don't generate spurious
If object modules from several programs are mixed together in an object
file specification, a single invocation of STRUCHART will produce several
structure charts. The
/MAIN command line option can be used
to selectively print the structure charts.
Generation of an output structure chart is based on a simple, depth-first search (DFS) algorithm that recursively visits each vertex in the call graph:
PROC dfs (x) IF visited[x] THEN RETURN visited[x] = true DO for each routine y that x calls CALL dfs (y) ENDDO ENDPROC
While the algorithm above is sufficient to perform a basic graph traversal, the structures of real programs usually introduce cycles and multiple paths into the graph, the presence of which would be usefully noted in the output structure chart.
Cycles are caused by recursive procedure calls (see Figure 3a) and are easily detected by locking a routine while its subtree is searched. The locked routines at any particular instant are those routines which lie on the current search path: the sequence of calls from the main routine down to the current routine. Visiting a locked routine (i.e., one which also appears earlier in the search path) is the sign of a recursive call and STRUCHART outputs an explicit message saying so.
In graph terminology, the number of edges entering a vertex is known
as the in-degree of the vertex. In STRUCHART, a module's
in-degree equals the length of its
CALLED_BY list and
is the number of different routines that directly call the module.
Multiple paths to a particular vertex, indicated by an in-degree
greater than one, are characteristic of utility routines called from
different modules in your program (see Figure 3b). Utility routines
are flagged with an asterisk (
*) in the output; a utility
routine's subtree is only expanded on the first visit to the routine
during the graph traversal.
An enhanced DFS algorithm handles
recursive calls and utility routines. Subroutine
DFS_PRINT, an iterative,
FORTRAN implementation of this algorithm, traverses the graph
and prints out the structure chart.
Six years of using STRUCHART have proven how invaluable the program is. On one project, we resurrected a large amount of VAX FORTRAN code written by a different group several years earlier. At the beginning of the project, submitting the recompiled programs to STRUCHART produced structure charts that were a great help in finding our way through the many pages of source code. At the end of the project, while updating the software documentation before its delivery to the customer, I used STRUCHART to generate "as-built" structure charts for our system. STRUCHART raced through 30-40 programs, with 30-100+ object modules each, in about 5 minutes; just imagine how long these updates would have taken if done manually!
Some more extraordinary applications of STRUCHART have taken advantage of its intermediate file. Although the separation of the object file scan from the building of the call graph, as was done in earlier versions of STRUCHART, seems to have added an unneccesary processing step, the ability to input the calling information from an arbitrary intermediate file served to free STRUCHART from the VAX sphere of influence. In one case, fancy footwork with a text editor enabled me to hack some PL/M-86 source files (stored on our VAX before being downloaded to an Intel development system) into a STRUCHART intermediate file that generated a usable structure chart for our non-VAX, embedded, real-time software.
More recently, I was handed a PDP-11 magnetic tape containing nearly 600 undocumented, FORTRAN source files (plus 100 INCLUDE files and 50 MACRO files) from an old satellite control center. I was able to read the tape on a Data General computer and transfer the files over a network to our Sun workstation, but where could I go from there? Hmmm ... STRUCHART ...
A couple of hours sufficed to write a C program that scanned the FORTRAN programs for subroutine declarations and calls and output a STRUCHART-readable intermediate file. The C program also picked up function declarations, but the small number of functions in the FORTRAN code did not warrant the complexity required to recognize function calls.
Porting STRUCHART to the Sun system was a real headache because the available FORTRAN compiler implemented a primitive version of FORTRAN-77 (to maintain compatibility with some third-party software, we were running an older version of Sun's operating system). After a few hours of work, however, I had STRUCHART up and running, minus object file processing and many of the amenities of VMS. A short while later, I had 700 routines divided up among structure charts for 120 programs. Not bad for a full day's work; now, if I could just figure out what all those 6-character variable names mean!
Improvements can always be made to any program and several ideas come to mind for STRUCHART. First and foremost would be to upgrade STRUCHART to distinguish and meaningfully handle object modules generated from different languages—a job that calls for someone intimately familiar with the compilers.
The list of prefixes used by STRUCHART to filter out the names of
frequently-called system routines (e.g.,
etc.) is hard-coded in subroutine
GET_SYMBOLS and was tailored
to our FORTRAN/MACRO programming environment. Other shops might wish to
modify this list as their needs require. An attractive alternative to
hard-coding the list is to set it up at run-time using command line options
or an initialization file.
Although I like STRUCHART's 8-space indentation of call levels, I frequently get lost in deeply-nested, multi-page structure charts. It's a simple matter, however, to edit the output file and add some type of level indicator. For example, the EDT command:
S / /. / WHOLE(replace 8 spaces by a dot and 7 spaces throughout the file) adds a vertical line of dots for each call level. STRUCHART's own structure chart looks as follows after this treatment:
STRUCHART . FPARSE * . TRIM * . SCAN_OLB . . READ_OLB . . . TRIM * . . . GET_SYMBOLS * . . . . ADD_ROUTINE * . . . . ADD_NODE * . . TRIM * . READ_SCI . . TRIM * . . GETWORD . . ADD_ROUTINE * . . ADD_NODE * . READ_OBJ . . FPARSE * . . TRIM * . . GET_SYMBOLS * . DFS_PRINT . . TRIM *
An automatic structure chart generator such as STRUCHART is a tool useful throughout the software life-cycle, from initial design through final testing and maintenance. Although computers such as the Macintosh have simplified the production of graphics, textual representation of information is, in some cases, able to convey the same information more concisely, as effectively, and with less effort. STRUCHART's techniques of graph traversal and textual output could be usefully employed in other applications as well, such as data flow diagrams, family trees, etc.
STRUCHART was written when the author worked for General Electric's Space Division (Lanham, MD); the program was ported to UNIX in the author's current position with Integral Systems, Inc. (Lanham, MD). Acknowledgement is due to my brother for his assistance in testing STRUCHART.
!************************************************************************** ! ! Command Language Definition file for the Structure Chart Generator. ! ! NOTE: Set the IMAGE argument to point to your copy of the ! STRUCHART executable. ! !************************************************************************** DEFINE VERB STRUCHART IMAGE "disk:[directory]struchart.exe" QUALIFIER DOLLARS, NEGATABLE QUALIFIER MAIN, VALUE (LIST,REQUIRED) QUALIFIER OUTPUT, VALUE (TYPE=$FILE) PARAMETER P1, VALUE (LIST,TYPE=$FILE,DEFAULT="*.obj")
C************************************************************************** PROGRAM STRUCHART C************************************************************************** C C STRUCHART is an automatic structure chart generator. It reads the C VAX/VMS object modules making up a program (or multiple programs), C extracts the global symbols defined in each object module, and builds C the structure chart(s) defined by that symbol information. C C************************************************************************** IMPLICIT NONE C... Parameters, global variables, and external definitions. INCLUDE 'struchart.inc' ! STRUCHART definitions. PARAMETER P_SCO_LUN = 9 ! Logical unit number for output file. EXTERNAL CLI$_ABSENT, CLI$_NEGATED, CLI$_PRESENT INTEGER*4 fparse, trim ! External functions. INTEGER*4 CLI$GET_VALUE, CLI$PRESENT, LIB$FIND_FILE C... Local variables. CHARACTER extension*4, main*32, message*128 CHARACTER output_file*128, source_file*128 CHARACTER sticky_defaults*128, wildcard_spec*128 INTEGER*4 context, i, length, status LOGICAL name_from_module C... Set flags based on command line options. status = CLI$PRESENT ('DOLLARS') IF (status .EQ. %LOC(CLI$_PRESENT)) THEN exclude_flag = P_NONE ! /DOLLARS - includes all $-routines. ELSEIF (status .EQ. %LOC(CLI$_NEGATED)) THEN exclude_flag = P_DOLLARS ! /NODOLLARS - excludes all $-routines. ELSE exclude_flag = P_DEFAULTS ! Otherwise, exclude default list only. ENDIF C... Initialize the adjacency list and the routine table to empty. NUM_ADJ = 0 NUM_ROUTINES = 0 C... Get the input file specifications from the command line. C Read each file and build the caller-callee data structure. sticky_defaults = ' ' DO WHILE (CLI$GET_VALUE ('P1', wildcard_spec) .NE. + %LOC(CLI$_ABSENT)) IF (fparse (wildcard_spec, %DESCR(';'), sticky_defaults, , , + source_file)) THEN wildcard_spec = source_file ENDIF context = 0 DO WHILE (LIB$FIND_FILE (wildcard_spec, source_file, context)) WRITE (6,*) source_file(1:trim(source_file)) CALL fparse (source_file, , , %DESCR('TYPE'), , extension) IF (extension .EQ. '.OLB') THEN CALL scan_olb (source_file) ! Object library. ELSEIF (extension .EQ. '.SCI') THEN CALL read_sci (source_file) ! Intermediate file. ELSE CALL read_obj (source_file) ! Object file. ENDIF ENDDO sticky_defaults = wildcard_spec ENDDO C... Open up the output file. If "/OUTPUT" was specified, base C the output file name on the main module name. If "/OUTPUT=filename" C was specified, open filename for output. If neither was specified, C write the structure charts out to SYS$OUTPUT. status = CLI$PRESENT ('OUTPUT') IF (status .EQ. %LOC(CLI$_PRESENT)) THEN status = CLI$GET_VALUE ('OUTPUT', output_file) IF (status .EQ. %LOC(CLI$_ABSENT)) THEN name_from_module = .TRUE. ! "/OUTPUT" ELSE name_from_module = .FALSE. ! "/OUTPUT=filename" OPEN (UNIT=P_SCO_LUN, name=output_file, TYPE='NEW', + CARRIAGECONTROL='LIST', IOSTAT=status, ERR=90) ENDIF ELSE name_from_module = .FALSE. ! Option not specified. output_file = 'SYS$OUTPUT' OPEN (UNIT=P_SCO_LUN, name=output_file, TYPE='NEW', + CARRIAGECONTROL='LIST', IOSTAT=status, ERR=90) ENDIF C... If the names of one or more main modules was specified on the C command line, generate a structure chart for each of the programs. C For each of the main routines, traverse that routine's subtree and C output its structure chart. If the output file names are to be C based on the main module names, open a new output file for each C main routine. IF (CLI$PRESENT ('MAIN') .NE. %LOC(CLI$_ABSENT)) THEN DO WHILE (CLI$GET_VALUE ('MAIN', main) .NE. %LOC(CLI$_ABSENT)) DO i = 1, num_routines IF (routine_name(i) .EQ. main) THEN IF (name_from_module) THEN CALL fparse (routine_name(i), %DESCR('.SCO'), + , , , output_file) OPEN (UNIT=P_SCO_LUN, name=output_file, + TYPE='NEW', CARRIAGECONTROL='LIST', + IOSTAT=status, ERR=90) ENDIF CALL dfs_print (i, P_SCO_LUN) IF (name_from_module) CLOSE (UNIT=P_SCO_LUN) ENDIF ENDDO ENDDO ELSE C... If no main modules were specified on the command line, generate C structure charts for all possible programs. For each "root" (a node C called by no other node) in the graph, traverse the tree below the C root and display that root's structure chart. If the output file C names are to be based on the main module names, open a new output C file for each root. DO i = 1, num_routines IF ((called_by(i) .EQ. NULL) .AND. ! A root node? + (defined_in(i) .NE. 'OLB')) THEN ! Not a library routine? IF (name_from_module) THEN CALL fparse (routine_name(i), %DESCR('.SCO'), + , , , output_file) OPEN (UNIT=P_SCO_LUN, name=output_file, + TYPE='NEW', CARRIAGECONTROL='LIST', + IOSTAT=status, ERR=90) ENDIF CALL dfs_print (i, P_SCO_LUN) IF (name_from_module) CLOSE (UNIT=P_SCO_LUN) ENDIF ENDDO ENDIF C... If there was an error opening up the output file, display C an error message. status = 0 ! No errors. 90 IF (status .NE. 0) THEN CALL ERRSNS ( , , , , status) WRITE (6,*) 'Error opening output file: "', + output_file(1:trim(output_file)), '"' CALL LIB$SYS_GETMSG (status, length, message, , ) WRITE (6,*) message(1:length) CALL EXIT ENDIF END
C************************************************************************** SUBROUTINE GET_SYMBOLS (current_module, file_type, + rec, record_length) C************************************************************************** C C Subroutine GET_SYMBOLS extracts calling hierarchy information from C a VMS object record. GET_SYMBOLS handles two types of VMS object C records: (i) main module header records and (ii) text information C and relocation records. Other record types are ignored. C C If a main module header (MHD) record is encountered, GET_SYMBOLS C extracts the module name, adds it to the routine table, and updates C the CURRENT_MODULE argument. C C If a text information and relocation (TIR) record is encountered, C GET_SYMBOLS scans the Linker instructions in the record, looking C for references to global symbols. For each reference found, C GET_SYMBOLS adds a "currentModule calls globalSymbol" C relation to the call graph. C C NOTE: GET_SYMBOLS is dependent upon the VMS object file format, C which is described in the VAX/VMS Linker Manual. Changes in C the file format might require changes in GET_SYMBOLS. C C C Example Usage (in Pseudo-Code): C C Open the object file C current_module = ' ' C DO WHILE (NOT EOF) C Read an object record from the object file C CALL get_symbols (current_module, 'OBJ', C object_record, length) C ENDDO C C C Arguments: C C CURRENT_MODULE (Character) C is the name of the current module. Initially this should C be spaced out (' '). As GET_SYMBOLS processes main module C header records, it will pull out the module name and store C it in this argument. C FILE_TYPE (Character) C is the type of the file from which the object record C was read: 'OBJ' for a ".OBJ" object file, and 'OLB' for C a ".OLB" object library. (See the DEFINED_IN field of C the routine table in the STRUCHART.INC include file.) C REC (Object record structure) C is the object record GET_SYMBOLS will scan. C RECORD_LENGTH (Integer) C is the length of the object record. C C************************************************************************** IMPLICIT NONE C... Parameters, global variables, and external definitions. INCLUDE '($MHDEF)' ! Module header record definition. INCLUDE '($OBJRECDEF)' ! Object language record definition. INCLUDE '($TIRDEF)' ! Text information and relocation record. INCLUDE 'struchart.inc' ! STRUCHART definitions. INTEGER*4 add_routine ! External function. C... Subroutine arguments. CHARACTER*(*) current_module CHARACTER*(*) file_type ! 'OBJ' or 'OLB'. STRUCTURE /OBJECT_RECORD/ UNION MAP CHARACTER text*(OBJ$C_MAXRECSIZ) END MAP MAP BYTE buffer(OBJ$C_MAXRECSIZ) END MAP MAP RECORD /MHDEF/ mhd ! Module header record. END MAP MAP RECORD /OBJRECDEF/ obj ! Object file record. END MAP MAP RECORD /TIRDEF/ tir ! Text info/reloc record. END MAP END UNION END STRUCTURE RECORD /OBJECT_RECORD/ rec INTEGER*4 record_length C... Local variables. CHARACTER*32 symbol INTEGER*4 calling_routine, command, i, length, ptr C************************************************************************** C C Data Length Table: C C The Data Length Table defines the lengths of the data fields C for the various Text Information and Relocation commands recognized C by the VMS Linker. Subroutine GET_SYMBOLS uses these lengths to C step through the command stream in a TIR record. Certain types of C commands which have variable length data fields are flagged with C a negative length in the table: C C -1 : Standard name (first byte = # of characters that follow) C -2 : Standard name + byte + argument descriptor C -3 : Word + standard name C -4 : Like standard name (first byte = # of bytes that follow) C C************************************************************************** INTEGER*4 data_length(0:127) DATA data_length(TIR$C_STA_GBL) /-1/ DATA data_length(TIR$C_STA_SB) / 1/ DATA data_length(TIR$C_STA_SW) / 2/ DATA data_length(TIR$C_STA_LW) / 4/ DATA data_length(TIR$C_STA_PB) / 2/ DATA data_length(TIR$C_STA_PW) / 3/ DATA data_length(TIR$C_STA_PL) / 5/ DATA data_length(TIR$C_STA_UB) / 1/ DATA data_length(TIR$C_STA_UW) / 2/ DATA data_length(TIR$C_STA_BFI) / 0/ DATA data_length(TIR$C_STA_WFI) / 0/ DATA data_length(TIR$C_STA_LFI) / 0/ ! Entry point mask from GSD$C_EPM subrecord? DATA data_length(TIR$C_STA_EPM) /-1/ DATA data_length(TIR$C_STA_CKARG) /-2/ DATA data_length(TIR$C_STA_WPB) / 3/ DATA data_length(TIR$C_STA_WPW) / 4/ DATA data_length(TIR$C_STA_WPL) / 6/ DATA data_length(TIR$C_STA_LSY) /-3/ DATA data_length(TIR$C_STA_LIT) / 1/ ! Entry point mask from GSD$C_LEPM record? DATA data_length(TIR$C_STA_LEPM) /-3/ DATA data_length(TIR$C_STO_SB) / 0/ DATA data_length(TIR$C_STO_SW) / 0/ DATA data_length(TIR$C_STO_L) / 0/ ! TIR$C_STO_LW DATA data_length(TIR$C_STO_BD) / 0/ DATA data_length(TIR$C_STO_WD) / 0/ DATA data_length(TIR$C_STO_LD) / 0/ DATA data_length(TIR$C_STO_LI) / 0/ DATA data_length(TIR$C_STO_PIDR) / 0/ DATA data_length(TIR$C_STO_PICR) / 0/ DATA data_length(TIR$C_STO_RSB) / 0/ DATA data_length(TIR$C_STO_RSW) / 0/ DATA data_length(TIR$C_STO_RL) / 0/ DATA data_length(TIR$C_STO_VPS) / 2/ DATA data_length(TIR$C_STO_USB) / 0/ DATA data_length(TIR$C_STO_USW) / 0/ DATA data_length(TIR$C_STO_RUB) / 0/ DATA data_length(TIR$C_STO_RUW) / 0/ DATA data_length(TIR$C_STO_B) / 0/ DATA data_length(TIR$C_STO_W) / 0/ DATA data_length(TIR$C_STO_RB) / 0/ DATA data_length(TIR$C_STO_RW) / 0/ DATA data_length(TIR$C_STO_RIVB) /-4/ DATA data_length(TIR$C_STO_PIRR) / 0/ DATA data_length(TIR$C_OPR_NOP) / 0/ DATA data_length(TIR$C_OPR_ADD) / 0/ DATA data_length(TIR$C_OPR_SUB) / 0/ DATA data_length(TIR$C_OPR_MUL) / 0/ DATA data_length(TIR$C_OPR_DIV) / 0/ DATA data_length(TIR$C_OPR_AND) / 0/ DATA data_length(TIR$C_OPR_IOR) / 0/ DATA data_length(TIR$C_OPR_EOR) / 0/ DATA data_length(TIR$C_OPR_NEG) / 0/ DATA data_length(TIR$C_OPR_COM) / 0/ DATA data_length(TIR$C_OPR_INSV) / 2/ DATA data_length(TIR$C_OPR_ASH) / 0/ DATA data_length(TIR$C_OPR_USH) / 0/ DATA data_length(TIR$C_OPR_ROT) / 0/ DATA data_length(TIR$C_OPR_SEL) / 0/ DATA data_length(TIR$C_OPR_REDEF) /-1/ DATA data_length(TIR$C_OPR_DFLIT) / 1/ DATA data_length(TIR$C_CTL_SETRB) / 0/ DATA data_length(TIR$C_CTL_AUGRB) / 4/ DATA data_length(TIR$C_CTL_DFLOC) / 0/ DATA data_length(TIR$C_CTL_STLOC) / 0/ DATA data_length(TIR$C_CTL_STKDL) / 0/ C... Lookup the current module name in the routine table and C save its index. IF (current_module .NE. ' ') THEN calling_routine = add_routine (current_module, ' ') ENDIF C... Main module header record. Extract the module name and C enter it in the routine table. IF ((rec.obj.OBJ$B_RECTYP .EQ. OBJ$C_HDR) .AND. + (rec.obj.OBJ$B_SUBTYP .EQ. MHD$C_MHD)) THEN length = ZEXT (rec.mhd.MHD$B_NAMLNG) current_module = rec.mhd.MHD$T_NAME(1:length) calling_routine = add_routine (current_module, file_type) C... Text information and relocation record. Extract the global C symbols referenced in the record. ELSEIF (rec.obj.OBJ$B_RECTYP .EQ. OBJ$C_TIR) THEN i = 2 DO WHILE (i .LE. record_length) command = rec.buffer(I) i = i + 1 ! Skip command byte. C... Extract the global symbol and add the module-calls-symbol C relation to the call graph. IF (command .EQ. TIR$C_STA_GBL) THEN length = ZEXT (rec.buffer(i)) symbol = rec.text(i+1:i+length) IF (exclude_flag .EQ. P_DEFAULTS) THEN IF (symbol(1:4) .EQ. 'FOR$') symbol = ' ' IF (symbol(1:4) .EQ. 'MTH$') symbol = ' ' IF (symbol(1:4) .EQ. 'OTS$') symbol = ' ' IF (symbol(1:4) .EQ. 'STR$') symbol = ' ' ELSEIF (exclude_flag .EQ. P_DOLLARS) THEN IF (INDEX (symbol, '$') .GT. 0) symbol = ' ' ENDIF IF (symbol .NE. ' ') THEN ! Not excluded? ptr = add_routine (symbol, ' ') CALL add_node (calling_routine, ptr) ENDIF ENDIF C... Step over the TIR command's operands to the next command. IF (command .LT. 0) THEN ! Store immediate command? i = i + ABS (command) ELSE length = data_length(command) IF (length .EQ. -1) THEN length = ZEXT (rec.buffer(i)) i = i + 1 + length ELSEIF (length .EQ. -2) THEN length = ZEXT (rec.buffer(i)) i = i + 1 + length + 1 + 1 length = ZEXT (rec.buffer(i)) i = i + 1 + length ELSEIF (length .EQ. -3) THEN i = i + 2 ! Skip word. length = ZEXT (rec.buffer(i)) i = i + 1 + length ELSEIF (length .EQ. -4) THEN length = ZEXT (rec.buffer(i)) i = i + 1 + length ELSE i = i + length ENDIF ENDIF ! If not a Store Immediate command. ENDDO ! Until the contents of the record are exhausted. ENDIF ! If a TIR record. RETURN END
Initially, for all routines x: visited[x] = false locked[x] = false PROC dfs (x, level) LOCAL y ; IF locked[x] THEN Indent (level) ; Print "Routine <x> is recursively called." ; ELSE IF visited[x] THEN Indent (level) ; Print "<x> *" ; The subtree below x was expanded on the first visit - do not expand it on subsequent visits ; ELSE IF in-degree[x] > 1 THEN Indent (level) ; Print "<x> *" ; ELSE Indent (level) ; Print "<x>" ; ENDIF visited[x] = true ; locked[x] = true ; DO for each routine y that x calls CALL dfs (y, level+1) ; ENDDO locked[x] = false ; ENDIF ENDIF ENDPROC
C************************************************************************** SUBROUTINE dfs_print (root, lun) C************************************************************************** C C Subroutine DFS_PRINT is the iterative implementation of a C recursive, depth-first search algorithm that visits and C prints out the nodes in a call graph. C C C Arguments: C C ROOT (Integer) C is the index in the routine table of the main module C at which the call tree traversal is to start. C LUN (Integer) C is the FORTRAN logical unit number to which the output C structure chart is to be written. C C************************************************************************** IMPLICIT NONE C... Parameters, global variables, and external definitions. INCLUDE 'struchart.inc' ! STRUCHART definitions. INTEGER*4 trim ! External function. C... Subroutine arguments. INTEGER*4 root INTEGER*4 lun C... Local variables. INTEGER*4 length, level, ptr, routine C... Initialize the graph structure attributes. DO routine = 1, num_routines locked(routine) = .FALSE. visited(routine) = .FALSE. ENDDO C... Beginning at the main routine (the root of the tree), C traverse the graph, printing out the calling structure of C the program. length = trim (routine_name(root)) WRITE (lun,500) routine_name(root)(1:length) 500 FORMAT (//A, /<length>('-'), /) routine = root stack_pointer = 0 DO WHILE (routine .GT. 0) length = trim (routine_name(routine)) level = (stack_pointer/2) + 1 ptr = NULL C... If the routine is locked (i.e., it also appears earlier in the C current search path), then a recursive call was made. Note that C fact in the output and "return". IF (locked(routine)) THEN WRITE (lun,510) routine_name(routine)(1:length) // + ' is recursively called.' 510 FORMAT (<(level-1)*8>X, A) ELSE C... If the routine has already been visited (i.e., it's a C utility-type function), then mark it in the output with an C asterisk and "return". The routine's subtree was expanded C on the first visit. IF (visited(routine)) THEN WRITE (lun,510) routine_name(routine)(1:length) // + ' *' ELSE C... On the first visit to a routine, print out its name and perform C a depth-first search of its subtree. IF (in_degree(routine) .GT. 1) THEN WRITE (lun,510) routine_name(routine)(1:length) + // ' *' ELSE WRITE (lun,510) routine_name(routine)(1:length) ENDIF visited(routine) = .TRUE. ptr = calls(routine) ENDIF ! Visited? ENDIF ! Locked? C... If a routine has no subtree or the subtree does not need C to be expanded (both conditions indicated by PTR = NULL), C then "return". If the expansion of the subtree of a routine C popped off the stack is complete, unlock the routine (i.e., C it's no longer on the current search path) and "return" again. DO WHILE ((ptr .EQ. NULL) .AND. (stack_pointer .GT. 0)) ptr = stack(stack_pointer) ! Pop (Routine, Ptr) stack_pointer = stack_pointer - 1 routine = stack(stack_pointer) stack_pointer = stack_pointer - 1 ptr = adj_link(ptr) IF (ptr .EQ. NULL) locked(routine) = .FALSE. ENDDO C... For each routine Y that X calls, lock X (i.e., X is on the C current search path), push X on the stack, and process Y. IF (ptr .EQ. NULL) THEN routine = -1 ELSE locked(routine) = .TRUE. stack_pointer = stack_pointer + 1 ! Push (Routine, Ptr) stack(stack_pointer) = routine stack_pointer = stack_pointer + 1 stack(stack_pointer) = ptr routine = adj_info(ptr) ENDIF ENDDO ! Until stack empty and no node. RETURN END