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Chapter 5 Program Analysis and DebuggingThis chapter presents a number of Sun Fortran compiler features that facilitate program analysis and debugging. Global Program CheckingThe f77 compiler's -Xlistx options provide a valuable way to analyze a source program for inconsistencies and possible runtime problems. The analysis performed by the compiler is global, across subprograms. -Xlistx reports errors in alignment, agreement in number and type for subprogram arguments, common block, parameter, and various other kinds of errors. -Xlistx also can be used to make detailed source code listings and cross-reference tables. Note - The f90 compiler provides only a subset of the --Xlist options described here. A conventional cross-reference map is produced, but complete global program checking is not performed. GPC OverviewGlobal program checking (GPC), invoked by the -Xlistx option, does the following:
In particular, global checking reports problems such as:
How to Invoke Global Program CheckingThe -Xlist option on the command line invokes the compiler's global program analyzer. There are a number of -Xlistx suboptions, as described in the sections that follow. Example: Compile three files for basic global program checking: demo% f77 -Xlist any1.f any2.f any3.f In the preceding example, the compiler:
Screen OutputNormally, output listings produced by -Xlistx are written to a file. To display directly to the screen, use -Xlisto to write the output file to /dev/tty. demo% f77 -Xlisto /dev/tty any1.f Default Output FeaturesThe -Xlist option provides a combination of features available for output. With no other -Xlist options, you get the following by default:
File TypesThe checking process recognizes all the files in the compiler command line that end in .f, .f90, .for, .F, or .o. The .o files supply the process with information regarding only global names, such as subroutine and function names. Analysis Files (.fln Files)Programs compiled with --Xlist options have their analysis data built into the binary files automatically. This enables global program checking over programs in libraries. Alternatively, the compiler will save individual source file analysis results into files with a .fln suffix if the -Xlistflndir option is also specified. dir indicates the directory to receive these files. demo% f77 -Xlistfln/tmp *.f Some Examples of --Xlist and Global Program CheckingHere is a listing of the Repeat.f source code used in the following examples: demo% cat Repeat.f
PROGRAM repeat
pn1 = REAL( LOC ( rp1 ) )
CALL subr1 ( pn1 )
CALL nwfrk ( pn1 )
PRINT *, pn1
END ! PROGRAM repeat
SUBROUTINE subr1 ( x )
IF ( x .GT. 1.0 ) THEN
CALL subr1 ( x * 0.5 )
END IF
END
SUBROUTINE nwfrk( ix )
EXTERNAL fork
INTEGER prnok, fork
PRINT *, prnok ( ix ), fork ( )
END
INTEGER FUNCTION prnok ( x )
prnok = INT ( x ) + LOC(x)
END
SUBROUTINE unreach_sub()
CALL sleep(1)
END
Example: Use -XlistE to show errors and warnings: demo% f77 -XlistE -silent Repeat.f
demo% cat Repeat.lst
FILE "Repeat.f"
program repeat
4 CALL nwfrk ( pn1 )
^
**** ERR #418: argument "pn1" is real, but dummy argument is
integer*4
See: "Repeat.f" line #14
4 CALL nwfrk ( pn1 )
^
**** ERR #317: variable "pn1" referenced as integer*4 across
repeat/nwfrk//prnok in line #21 but set as real
by repeat in line #2
subroutine subr1
10 CALL subr1 ( x * 0.5 )
^
**** WAR #348: recursive call for "subr1". See dynamic calls:
"Repeat.f" line #3
subroutine nwfrk
17 PRINT *, prnok ( ix ), fork ( )
^
**** ERR #418: argument "ix" is integer*4, but dummy argument
is real
See: "Repeat.f" line #20
subroutine unreach_sub
24 SUBROUTINE unreach_sub()
^
**** WAR #338: subroutine "unreach_sub" isn't called from program
Date: Wed Feb 24 10:40:32 1999
Files: 2 (Sources: 1; libraries: 1)
Lines: 26 (Sources: 26; Library subprograms:2)
Routines: 5 (MAIN: 1; Subroutines: 3; Functions: 1)
Messages: 5 (Errors: 3; Warnings: 2)
demo%
Compiling the same program with --Xlist also produces a cross-reference table on standard output: C R O S S R E F E R E N C E T A B L E
Source file: Repeat.f
Legend:
D Definition/Declaration
U Simple use
M Modified occurrence
A Actual argument
C Subroutine/Function call
I Initialization: DATA or extended declaration
E Occurrence in EQUIVALENCE
N Occurrence in NAMELIST
P R O G R A M F O R M
Program
-------
repeat <repeat> D 1:D
Functions and Subroutines
-------------------------
fork int*4 <nwfrk> DC 15:D 16:D 17:C
int intrinsic
<prnok> C 21:C
loc intrinsic
<repeat> C 2:C
<prnok> C 21:C
nwfrk <repeat> C 4:C
<nwfrk> D 14:D
prnok int*4 <nwfrk> DC 16:D 17:C
<prnok> DM 20:D 21:M
real intrinsic
<repeat> C 2:C
sleep <unreach_sub> C 25:C
subr1 <repeat> C 3:C
<subr1> DC 8:D 10:C
unreach_sub <unreach_sub> D 24:D
Output from compiling f77 -Xlist Repeat.f (Continued) Variables and Arrays
--------------------
ix int*4 dummy
<nwfrk> DA 14:D 17:A
pn1 real*4 <repeat> UMA 2:M 3:A 4:A 5:U
rp1 real*4 <repeat> A 2:A
x real*4 dummy
<subr1> DU 8:D 9:U 10:U
<prnok> DUA 20:D 21:A 21:U
----------------------------------------------------------------------
Date: Tue Feb 22 13:15:39 1995
Files: 2 (Sources: 1; libraries: 1)
Lines: 26 (Sources: 26; Library subprograms:2)
Routines: 5 (MAIN: 1; Subroutines: 3; Functions: 1)
Messages: 5 (Errors: 3; Warnings: 2)
demo%
In the cross-reference table in the preceding example:
Suboptions for Global Checking Across RoutinesThe basic global cross-checking option is -Xlist with no suboption. It is a combination of suboptions, each of which could have been specified separately. The following sections describe options for producing the listing, errors, and cross-reference table. Multiple suboptions may appear on the command line. Suboption SyntaxAdd suboptions according to the following rules:
--Xlist and its SuboptionsCombine suboptions according to the following rules:
Example: Each of these two command lines performs the same task: demo% f77 -Xlistc -Xlist any.f demo% f77 -Xlistc any.f The following table shows the reports generated by these basic --Xlist suboptions alone: Table 5-1 Xlist Suboptions
The following table summarizes all -Xlist suboptions. Table 5-2 Summary of --Xlist Suboptions
-Xlist Suboption ReferenceThis section describes the --Xlist suboptions. As noted, some are only available with f77. -f77: -Xlistc -- Show call graphs and cross-routine errorsUsed alone, --Xlistc does not show a listing or cross-reference. It produces the call graph in a tree form, using printable characters. If some subroutines are not called from MAIN, more than one graph is shown. Each BLOCKDATA is printed separately with no connection to MAIN. The default is not to show the call graph. --XlistE - Show cross-routine errorsUsed alone, --XlistE shows only cross-routine errors and does not show a listing or a cross-reference. - -Xlisterr[nnn] - Suppress error nnnUse --Xlisterr to suppress a numbered error message from the listing or cross-reference. For example: -Xlisterr338 suppresses error message 338. If nnn is not specified, all error messages are suppressed. To suppress additional specific errors, use this option repeatedly. f77: -Xlist-f - Produce faster outputUse --Xlistf to produce source file listings and a cross-checking report and to verify sources, but without generating object files. The default without this option is to generate object files. f77: -Xlist-flndir - Put .fln files into dir directoryUse --Xlistfln to specify the directory to receive .fln source analysis files. The directory specified (dir) must already exist. The default is to include the source analysis information directly within the object .o files (and not generate .fln files). f77: -Xlist-h - Halt on errorsWith --Xlisth, compilation stops if errors are detected while cross-checking the program. In this case, the report is redirected to stdout instead of the *.lst file. -Xlist-I - List and cross-check include filesIf -XlistI is the only suboption used, include files are shown or scanned along with the standard -Xlist output (line numbered listing, error messages, and a cross-reference table).
-Xlist-L - Show listing and cross routine errorsUse --XlistL to produce only a listing and a list of cross routine errors. This suboption by itself does not show a cross reference table. The default is to show the listing and cross reference table. -Xlist-ln - Set the page length for pagination to n linesUse --Xlistl to set the page length to something other than the default page size. For example, -Xlistl45 sets the page length to 45 lines. The default is 66. With n=0 (-Xlistl0) this option shows listings and cross-references with no page breaks for easier on-screen viewing. -Xlist-o name - Rename the -Xlist output report fileUse --Xlisto to rename the generated report output file. (A space between o and name is required.) With --Xlisto name, the output is to name.lst . To display directly to the screen, use the command: -Xlisto /dev/tty f77: -Xlist-s - Suppress unreferenced identifiersUse --Xlists to suppress from the cross reference table any identifiers defined in the include files but not referenced in the source files. This suboption has no effect if the suboption -XlistI is used. The default is not to show the occurrences in #include or INCLUDE files. f77: -Xlist-vn - Set level of checking strictnessn is 1,2, 3, or 4. The default is 2 (-Xlistv2):
-Xlist-w[nnn] - Set width of output line to n columnsUse --Xlistw to set the width of the output line. For example, -Xlistw132 sets the page width to 132 columns. The default is 79. -Xlist-war[nnn] - Suppress warning nnn in the reportUse --Xlistwar to suppress a specific warning message from the output reports. If nnn is not specified, then all warning messages are suppressed from printing. For example, -Xlistwar338 suppresses warning message number 338. To suppress more than one, but not all warnings, use this option repeatedly. -Xlist-X - Show cross-reference table and cross routine errors--XlistX produces a cross reference table and cross routine error list but no source listing. Some Examples Using SuboptionsExample: Use -Xlistwarnnn to suppress two warnings from a preceding example: demo% f77 -Xlistwar338 -Xlistwar348 -XlistE -silent Repeat.f
demo% cat Repeat.lst
FILE "Repeat.f"
program repeat
4 CALL nwfrk ( pn1 )
^
**** ERR #418: argument "pn1" is real, but dummy argument is
integer*4
See: "Repeat.f" line #14
4 CALL nwfrk ( pn1 )
^
**** ERR #317: variable "pn1" referenced as integer*4 across
repeat/nwfrk//prnok in line #21 but set as real
by repeat in line #2
subroutine nwfrk
17 PRINT *, prnok ( ix ), fork ( )
^
**** ERR #418: argument "ix" is integer*4, but dummy argument
is real
See: "Repeat.f" line #20
Date: Wed Feb 24 10:40:32 1999
Files: 2 (Sources: 1; libraries: 1)
Lines: 26 (Sources: 26; Library subprograms:2)
Routines: 5 (MAIN: 1; Subroutines: 3; Functions: 1)
Messages: 5 (Errors: 3; Warnings: 2)
demo%
Example: Explain a message and find a type mismatch in program ShoGetc.f: demo% cat ShoGetc.f
CHARACTER*1 c
i = getc(c)
END
demo% f77 -silent ShoGetc.f Compile program
demo% a.out Program waits for input...
Z Type "Z" on keyboard. This causes run-time message. Why?
Note: IEEE floating-point exception flags raised:
Invalid Operation;
See the Numerical Computation Guide, ieee_flags(3M)
demo% f77 -XlistE -silent ShoGetc.f Compile with Global Program Checking
demo% cat ShoGetc.lst and view listing
FILE "ShoGetc.f"
program MAIN
2 i = getc(c)
^
**** WAR #320: variable "i" set but never referenced
2 i = getc(c)
^
**** ERR #412: function "getc" used as real but declared as
integer*4
Here is the error - function must be declared INTEGER.
2 i = getc(c)
^
**** WAR #320: variable "c" set but never referenced
demo% cat ShoGetc.f Modify program to declare getc INTEGER and run again.
CHARACTER*1 c
INTEGER getc
i = getc(c)
END
demo% f77 -silent ShoGetc.f
demo% a.out
Z Type "Z" on keyboard
demo% Now no error.
Special Compiler OptionsSome compiler options are useful for debugging. They check subscripts, spot undeclared variables, show stages of the compile-link sequence, display versions of software, and so on. The Solaris linker has additional debugging aids. See ld(1), or run the command ld -Dhelp at a shell prompt to see the online documentation. Subscript Bounds (-C)The -C option adds checks for out-of-bounds array subscripts. If you compile with -C, the compiler adds checks at runtime for out-of-bounds references on each array subscript. This action helps catch some situations that cause segmentation faults. demo% cat indrange.f
REAL a(10,10)
k = 11
a(k,2) = 1.0
END
demo% f77 -C -silent indrange.f
demo% a.out
Subscript out of range on file indrange.f, line 3, procedure MAIN.
Subscript number 1 has value 11 in array a.
Abort (core dumped)
demo%
f77: Undeclared Variable Types (-u)The -u option checks for any undeclared variables. (Not available with f90.) The -u option causes all variables to be initially identified as undeclared, so that all variables that are not explicitly declared by type statements, or by an IMPLICIT statement, are flagged with an error. The -u flag is useful for discovering mistyped variables. If -u is set, all variables are treated as undeclared until explicitly declared. Use of an undeclared variable is accompanied by an error message. Version Checking (-V)The -V option causes the name and version ID of each phase of the compiler to be displayed. This option can be useful in tracking the origin of ambiguous error messages and in reporting compiler failures, and to verify the level of installed compiler patches. Interactive Debugging With dbx and Sun WorkShopThe Sun WorkShop provides a tightly integrated development environment for building and browsing, as well as debugging applications written in Fortran, C, and C++. The Sun WorkShop debugging facility is a window-based interface to dbx, while dbx itself is an interactive, line-oriented, source-level symbolic debugger. Either can be used to determine where a program crashed, to view or trace the values of variables and expressions in a running code, and to set breakpoints. Sun WorkShop adds a sophisticated graphical environment to the debugging process that is integrated with tools for editing, building, and source code version control. It includes a data visualization capability to display and explore large and complex datasets, simulate results, and interactively steer computations. For details, see the Sun manuals Using Sun WorkShop and Debugging a Program With Sun WorkShop, and the dbx(1) man pages. The dbx program provides event management, process control, and data inspection. You can watch what is happening during program execution, and perform the following tasks:
To debug optimized programs, use the dbx fix command to recompile the routines you want to debug:
Some optimizations will be inhibited by the presence of --g on the compilation command. For example, --g suppresses the automatic inlining usually obtained with- -O4. --g cancels any parallelization option (--autopar, --explicitpar, --parallel), as well as --depend and --reduction. Debugging is facilitated by specifying --g without any optimization options. See the dbx documentation for details. f77: Viewing Compiler Listing DiagnosticsUse the error utility program to view compiler diagnostics merged with the source code. error inserts compiler diagnostics above the relevant line in the source file. The diagnostics include the standard compiler error and warning messages, but not the -Xlist error and warning messages. Note - The error utility rewrites your source files and does not work if the source files are read-only, or are in a read only directory. error(1) is included as part of a "developer" installation of the Solaris operating environment; it can also be installed from the package, SUNWbtool. Facilities also exist in the Sun WorkShop for viewing compiler diagnostics. Refer to Using Sun WorkShop. |
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