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C Programming Tools

C Programming Tools. Lecturer: Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954. “UNIX for Programmers and Users” Third Edition, Prentice-Hall, GRAHAM GLASS, KING ABLES Slides partially adapted from Kumoh National University of Technology (Korea) and NYU.

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C Programming Tools

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  1. C Programming Tools Lecturer: Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954 “UNIX for Programmers and Users” Third Edition, Prentice-Hall, GRAHAM GLASS, KING ABLES Slides partially adapted from Kumoh National University of Technology (Korea) and NYU

  2. • Tools that support the various stages of program development: compilation, debugging, maintaining libraries, profiling, and source code control. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  3.  The C Languages - K&R C - ANSI C Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  4.  SINGLE-MODULE PROGRAMS We will analyze a simple C program: - performs a simple task: reversing a string. - how to write, compile, link, and execute a program that solves the problem using a single source file. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  5. - source-code listing of the first version of the “reverse” program (“reversefirst.c” on the Web) /* REVERSE.C */ #include <stdio.h> /* Function Prototype */ void reverse(); /*****************************************/ main() { char str[100]; /* Buffer to hold reversed string */ reverse(“cat”, str); /* Reverse the string “cat” */ printf(“reverse (“cat”)=%s\n”, str); /* Display Result */ reverse(“noon”, str); /* Reverse the string “noon” */ printf(“reverse (“noon”) = %s\n”, str); /* Display Result */ } /****************************************/ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  6. void reverse(before, after) char *before; /* A pointer to the source string */ char *after; /* A pointer to the reversed string */ { int i; int j; int len; len = strlen( before ); for( j=len-1; i=0; j>=0; j--; i++) /* Reverse loop */ after[i] = before[j]; after[len] = NULL; /* NULL terminate reversed string */ } Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  7.  Compiling a C Program - To create and run the “reverse” program, 1) create a subdirectory called “reverse” inside your home directory. 2) create the file “reversefirst.c” using the vi editor 3) compile the C program using the cc utility. - By default, cc creates an executable file called “a.out” in the current directory. To run the program, type “./a.out”. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  8.  Compiling a C Program ( Continue ) - Any errors that are encountered are sent to the standard error channel, which is connected by default to your terminal’s screen. $ mkdir reverse $ cd reverse $ vi reversefirst.c … $ cc reversefirst.c “reversefirst.c”, line 16: syntax error at or near variable name “cat” “reversefirst.c”, line 18: syntax error at or near variable name “noon” “reversefirst.c”, line 35: syntax error at or near symbol ; “reversefirst.c”, line 35: syntax error at or near symbol ) $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  9.  Compiling a C Program ( Continue ) - cc found a number of compile-time errors:  The errors on line 16 and 18 due to inappropriate use of double quotes within double quotes.  The errors one line 35 were due to an illegal use of a semicolon(;). - Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  10.  A Listing of the Corrected “Reverse” Program /* REVERSE.C */ #include <stdio.h> /* Function Prototype */ void reverse(); /******************************************/ main() { char str[100]; /* Buffer to hold reversed string */ reverse(“cat”, str); /* Reverse the string “cat” */ printf(“reverse (\” cat \” ) = %s \n”, str); /* Display */ reverse(“noon”, str); /* Reverse the string “noon” */ printf(“reverse (\” noon \” ) = %s \n”, str); /* Display */ } /*****************************************/ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  11. void reverse(before, after) char *before; /* A pointer to the source string */ char *after; /* A pointer to the reversed string */ { int i; int j; int len; len = strlen(before); for( j=len -1, i=0; j>=0; j--,j++) /* Reverse loop */ after[i] = before[j]; after[len]=NULL; /* NULL terminate reversed string */ ) Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  12.  Running a C Program - After compiling the second version of “reverse.c”, by typing the name of the executable file, “./a.out”. $ cc reverse.c $ ls -l reverse.c a.out -rwxr-xr-x 1 glass 24576 Jan5 16:16 a.out* -rw-r--r-- 1 glass 439 Jan5 16:15 reverse.c $ ./a.out reverse (“cat”) = tac reverse (“noon”) = noon $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  13.  Overriding the Default Executable Name - to use the “-o” option with cc, which allows you to specify the name of the executable file that you wish to create: $ cc reverse.c -o reverse $ ls -l reverse -rwx-xr-x 1 glass 24576 Jan 5 16:19 reverse* $ ./reverse reverse(“cat”) = tac reverse(“noon”) = noon $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  14.  MULTIMODULE PROGRAMS - The trouble with the “reverse” program, the “reverse” function cannot easily be used in other programs. - to write a function that returns a value of 1 if a string is a palindrome and a value of 0 otherwise. - A palindrome a string that reads the same forward and backward; for example, “noon” is a palindrome, but “nono” is not. - use the “reverse” function to implement our “palindrome” function. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  15.  Reusable Functions - A better strategy for sharing “reverse()”, 1) compile it separately, 2) and then link the resultant object module into whichever programs wish to use it. - this technique allows the function to be used in many different programs. Functions with this property are termed reusable functions. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  16.  Preparing a Reusable Function - To prepare a reusable function, 1) create a source-code module that contains the source code of the function, together with a header file that contains the function’s prototype. 2) compile the source-code module into an object module by using the “-c” option of cc. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  17.  Preparing a Reusable Function - reverse.h /* REVERSE.H */ void reverse(); /* Declare but do not define this function */ - reverse.c /* REVERSE.C */ #include <stdio.h> #include “reverse.h” /********************************************/ void reverse( before, after ) char *before; /* A pointer to the original string */ char *after; /* A pointer to the reversed string */ { int i; int j; int len; Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  18. len = strlen(before); for( j=len-1, i=0; j>=0; j--, j++) /* Reverse loop */ after[i] = before[j]; after[len] = NULL; /* NULL terminate reversed string */ } - main1.c /* MAIN1.C */ #include <stdio.h> #include “reverse.h” /* Contains the protype of reverse() */ /***********************************************/ main() { char str[100]; reverse(“cat”, str); /* Invoke external function */ printf(“reverse (\”cat\”) = %s\n”, str); reverse(“noon”,str); /* Invoke external function */ printf(“reverse (\”noon\”) = %s\n”, str); } Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  19.  Separately Compiling and Linking Modules - To compile each source-code file separately, use the “-c” option for cc. creates a separate object module for each source-code file, each with a “.o” suffix. $ cc -c reverse.c $ cc -c main1.c $ ls -l reverse.o mail1.o -rw-r--r-- 1 glass 311 Jan 5 18:24 main1.o -rw-r--r-- 1 glass 181 Jan 5 18:08 reverse.o $ - - place all of the source-code files on one line. $ cc -c reverse.c main1.c $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  20.  Separately Compiling and Linking Modules - To link them all together into an executable called “main1”, list the names of all of the object modules after the cc command: $ cc reverse.o main1.o -o main1 $ ls -l main1 -rwxr-xr-x 1 glass 24576 Jan 5 18:25 main1* $ ./main1 reverse (“cat”) = tac reverse (“noon”) = noon $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  21.  The Stand-alone Loader: ld - When cc is used to link several object modules, it transparently invokes the UNIX stand-alone loader, ld, to do the job. - The loader is better known as the linker. ld -n {-Lpath}* {objModule}* {library}* {-lx}* [-o outputFile] ld links together the specified object and library modules to produce an executable file. -n : if you wish to create a stand-alone executable -o : override the default name of the executable, “a.out”, -lx : searches the standard directories “/lib”, “/usr/lib”, and “/usr/local/lib” for a library with the name “libx.a”. -Lpath : to insert the directory path into this search path. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  22.  Separately Compiling and Linking Modules - If you link a C program manually, it’s important to specify the C runtime object module, “/lib/crt0.o”, $ ld -n /lib/crt0.o mina1.o reverse.o -lc -o main1 $ main1 reverse (“cat”) = tac reverse (“noon”) = noon $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  23.  Reusing the Reverse Function - Here’s the header and source-code listing of the “palindrome” function: palindrome.h /* PALINDROME.H */ int palindrome(); /* Declare but do not define */ palindrome.c /* PALINDROME.C */ #include “palindrome.h” #include “reverse.h” #include <string.h> /***********************************************/ int palindrome(str) char *str; { Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  24. char reverseStr[100]; reverse( str, reversedStr ); /* Reverse original */ return ( strcmp(str, reversedStr ) == 0 ); /* Compare the two */ } - the program main2.c that tests “palindrome()” /* MAIN2.C */ #include <stdio.h> #include “palindrome.h” /*************************************************/ main() { printf(“palindrome (\”cat\”) = %d \n”, palindrome(“cat”) ); printf(“palindrome (\”noon\”) = %d \n”, palindrome(“noon”) ); } Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  25. - To combine the “reverse”, “palindrome”, and “main2” modules Compile the object modules and then link them. $ cc -c palindrome.c $ cc -c main2.c $ cc reverse.o palindrome.o main2.o -o main2 -rwxr-xr-x 1 glass 24576 Jan 5 19:09 main2* -rw-r--r-- 1 glass 306 Jan 5 19:00 main2.o -rw-r--r-- 1 glass 189 Jan 5 18:59 palindrome.o -rw-r--r-- 1 glass 181 Jan 5 18:08 reverse.o $ main2 palindrome (“cat”) = 0 palindrome (“noon”) = 1 $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  26.  Maintaining Multimodule Programs - Several different issues must be considered when maintaining multimodule systems: Q1. What ensures that object modules and executables are kept up to date? Q2. What stores the object modules? Q3. What tracks each version of source and header files? A1. make, the UNIX file-dependency system A2. ar, the UNIX archive system A3. cvs, the Concurrent Version System Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  27. Debugging Programswithgdb: GNU Debugger

  28.  THE UNIX PROFILER: PROF - To see where a program is spending its time. - If an amount of time that is greater than expected is being spent in a particular function, it might be worth optimizing the function by hand for better performance. Utility : prof -ln [ executableFile [profileFile] ] prof is the standard UNIX profiler. It generates a table of time and repetitions of each function in the executable executableFile based on the performance trace stored in the file profileFile. if profileFile is omitted, the filename “mon.out” is assumed. Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  29.  THE UNIX PROFILER: PROF - The executable file must have been compiled using the -p option of cc , which instructs the compiler to generate special code that writes a “mon.out” file when the program runs. $ cc -p main2.c $ main2---> execute the program. palindrome (“cat”) = 0 ---> program output. palindrome (“noon”) = 1 $ ls -l mon.out---> list the file for monitor output. -rw-r-xr-x 1 gglass 1472 Jan 8 17:19 mon.out $ prof main2 mon.out---> profile the program. %Time Seconds Cumsecs #Calls msec/call Name 42.9 0.05 0.05 rdpcs 42.9 0.05 0.10 2002 0.025 reverse 14.3 0.02 0.12 2002 0.008 palindrome 0.0 0.00 0.12 1 0. main Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  30.  THE UNIX PROFILER: PROF $ prof -l main2---> order the profile by name. %Time Seconds Cumsecs #Calls msec/call Name 0.0 0.00 0.05 1 0. main 14.3 0.02 0.07 2002 0.008 palindrome 42.9 0.05 0.05 rdpcs 42.9 0.05 0.12 2002 0.025 reverse $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  31.  DOUBLE-CHECKING PROGRAMS: LINT - checks your program more thoroughly than cc does: Utility : lint { fileName }* lint scans the specified source files and displays any potential errors that it finds. $ lint reverse.c---> check “reverse.c”. reverse defined ( reverse.c(12) ), but never used $ lint palindrome.c---> check “palindrome.c”. palindrome defined ( palindrome.c ( 12 ) ), but never used reverse used ( palindrome.c(14) ), but not defined Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  32.  DOUBLE-CHECKING PROGRAMS: LINT $ lint main2.c---> check “main2.c”. main2.c(11) : warning: main() returns random value to invocation environment printf returns value which is always ignored palindrome used ( main2.c(9) ), but not defined $ lint main2.c reverse.c palindrome.c---> check all modules together. main2.c: min2.c(11): warning: main() returns random value to invocation environment reverse.c: palindrome.c: Lint pass2: printf returns value which is always ignored $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  33.  When you’re done: STRIP - The debugger and profiler, utilities both require that you compile a program using special options, each of which adds code to the executable file. remove this extra code after debugging and profiling are done with, Utility: strip { fileName }+ strip removes all of the symbol table, relocation, debugging, and profiling information from the named file(s). Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  34.  When you’re done: STRIP - an example of how much space you can save by using strip: $ ls -l main2---> look at original file. -rwxr-xr-x 1 gglass 5904 Jan 8 22:18 main2* $ strip main2---> strip out spurious information. $ ls -l main2---> look at stripped version. -rwxr-xr-x 1 gglass 3373 Jan 8 23:17 main2* $ _ Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  35. Tracing System Calls • Most operating systems contain a utility to monitor system calls: • HPUX: tusc, MAC OS X: ktrace, Linux: strace, Solaris: truss, SGI: par 27mS[ 1] : close(0) OK 27mS[ 1] : open("try.in", O_RDONLY, 017777627464) 29mS[ 1] : END-open() = 0 29mS[ 1] : read(0, "1\n2\n|/bin/date\n3\n|/bin/sleep 2", 2048) = 31 29mS[ 1] : read(0, 0x7fff26ef, 2017) = 0 29mS[ 1] : getpagesize() = 16384 29mS[ 1] : brk(0x1001c000) OK 29mS[ 1] : time() = 1003207028 29mS[ 1] : fork() 31mS[ 1] : END-fork() = 1880277 41mS[ 1] (1864078): was sent signal SIGCLD 31mS[ 2] : waitsys(P_ALL, 0, 0x7fff2590, WTRAPPED|WEXITED, 0) 42mS[ 2] : END-waitsys(P_ALL, 0, {signo=SIGCLD, errno=0, code=CLD_EXITED, pid=1880277, status=0}, WTRAPPED|WEXITED, 0) = 0 42mS[ 2] : time() = 1003207028 Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

  36.  CHAPTER REVIEW In this chapter, we learned how to:  Compile C programs  manage the compilation of multimodule programs  maintain archives  maintain multiple versions of source code  profile executable files  debug executable files Prof. Andrzej (AJ) Bieszczad Email: andrzej@csun.edu Phone: 818-677-4954

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