Chapter 12 C Programming Tools

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Chapter 12C Programming Tools

• Graham Glass and King Ables,
• UNIX for Programmers and Users,
• Third Edition, Pearson Prentice Hall, 2003.
• Original Notes by Raj Sunderraman
• Converted to presentation and updated by Michael
  Weeks

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Compiling in gcc

• GNU C Compiler (gcc)?
• http//www.gnu.org

gcc reverse.c produces executable in a.out
gcc -o reverse reverse.c
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Multi-module Program

• types.h supps.h, supps.c parts.h, parts.c sp.h,
  sp.c db.h, db.c (this has the main() function)?
• Compile these programs separately
• gcc -c supps.c
• gcc -c parts.c
• gcc -c sp.c
• gcc -c db.c
• These commands produce supps.o, parts.o, sp.o,
  db.o
• gcc db.o supps.o parts.o sp.o -o db

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Unix File-Dependency System make

• make -f fileName
• Makefiles consist of a list of interdependency
  rules of the form
• targetListdependencyList
• commandList
• Rules must be separated by at least one line

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Unix File-Dependency System make

• targetList is a list of target files
• dependencyList is a list of files on which the
  files in targetList depend on
• commandList is a list of zero or more commands,
  separated by new lines, that reconstruct the
  target files from the dependency files
• NOTE Each line in commandList MUST start with a
  tab

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Example Makefile
db db.o supps.o parts.o sp.o gcc
db.o supps.o parts.o sp.o -o db db.o db.c
types.h db.h supps.h parts.h sp.h gcc -c
db.c supps.o supps.c types.h supps.h
gcc -c supps.c parts.o parts.c types.h
parts.h gcc -c parts.c sp.o sp.c
types.h sp.h gcc -c sp.c
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Order of Make rules

• The order of make rules is important. The make
  utility starts from the first rule and creates a
  tree with target files at the root and the
  dependency files as children.

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Order of Make rules

• The make utility then works up the tree
• From the leaf nodes to the root node
• Looking to see if the last modification time of
  each node is more recent than the last
  modification time of the immediate parent node
• If so, the associated parent's rule is executed

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Make Rules

• Make Rules of the form
• xxx.o reverse.c reverse.h
• gcc -c xxx.c
• where xxx varies from each rule
• Pre-defined rule (how to make .o from .c files)
• .c.o
• /bin/cc -c -O lt

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Simplifying Make Files

• So makefile can be simplified as

db db.o supps.o parts.o sp.o gcc db.o
supps.o parts.o sp.o -o db db.o db.c types.h
db.h supps.h parts.h sp.h supps.o supps.c
types.h supps.h parts.o parts.c types.h
parts.h sp.o sp.c types.h sp.h
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Simplifying Make Files

• Further simplification (leave out .c files in
  dependency rules

db db.o supps.o parts.o sp.o gcc db.o
supps.o parts.o sp.o -o db db.o types.h db.h
supps.h parts.h sp.h supps.o types.h supps.h
parts.o types.h parts.h sp.o types.h sp.h
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Touch Utility

• touch -c fileName
• updates the last modification and access times of
  the named files to the current time.
• By default, if a specified file does not exist it
  is created with zero size.
• To prevent this default, use -c option.
• Use touch to force make to recompile files

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Archiving Modules

• GNU archive utility ar
• ar key archivename file
• Creates archive files (.a)?
• Add (r, if file is not there)?
• Remove (d)?
• Replace (r)?
• Append (q) adds to end of archive
• Table of contents (t)?

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GNU Profiler

• Utility gprof profiles a running program
• lets you see how the program spends its time
• Must use -pg option with gcc
• Creates file gmon.out by default

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GNU Debug

• Utility gdb helps debug a program
• Must use -g option when compiling
• gdb programname
• Get help (help)?
• Set breakpoints (break line_or_function)?
• Look at variables (print variable_name)?
• Run a program (run, step, or continue after
  breakpoint)?
• List a program (list)?

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Strip Utility

• Utility strip removes extra info from a program
• Useful after debug / profile
• strip programname

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Review

• Compiling .c files
• Including multiple files
• Using make to compile several related files
• How to simplify an example makefile
• touch command