ch3-Debugging

Chapter_3     ch3-Pointers                                                                            ch3-Function_Addresses 

Contents:

ch3-DynamicDebugFlags     ch3-StringizingExpressions     Exercise_3-31     ch3-Assert

Note:  See also Exercise_3-35 in Section ch3-Make. 

ch3-DynamicDebugFlags     TCP1, p. 209-210

Contents:     dynamic_debug_flags.c     DynamicDebugFlags.cpp

dynamic_debug_flags.c          download

#include <stdio.h> // for printf(), scanf()

#include <string.h> // for strcmp()

typedef enum {FALSE, TRUE} bool; // user-defined typename

// Debug flags aren't necessarily global:

bool debug = FALSE;

int main(int argc, char* argv[])

{

  int i;

  for(i = 0; i < argc; i++)

  {

    if(strcmp(argv[i], "--debug=on") == 0)

    {

      debug = TRUE;

      break; // out of for()

    }

  }

  bool go = TRUE;

  char reply[10];

  while(go)

  {

    if(debug)

    {

      // Debugging code here

      printf("Debugger is now on!\n");

    }

    else

    {

      printf("Debugger is now off.\n");

    }

    printf("Turn debugger [on/off/quit]: ");

    scanf("%s", reply);

    if(strcmp(reply, "on") == 0) {debug = TRUE;} // Turn it on

    else if(strcmp(reply, "off") == 0) {debug = FALSE;} // Off

    else if(strcmp(reply, "quit") == 0) {break;} // Out of while(), end program

  }

  return 0;

}

/*

// g++ dynamic_debug_flags.c // error: redefining built-in type `bool'

// gcc OK with used-defined typename `bool':

gcc dynamic_debug_flags.c -o dynamic_debug_flags

./dynamic_debug_flags

Debugger is now off.

Turn debugger [on/off/quit]: on

Debugger is now on!

Turn debugger [on/off/quit]: off

Debugger is now off.

Turn debugger [on/off/quit]: q

Debugger is now off.

Turn debugger [on/off/quit]: quit

./dynamic_debug_flags --debug=on

Debugger is now on!

Turn debugger [on/off/quit]: q

Debugger is now on!

Turn debugger [on/off/quit]: on

Debugger is now on!

Turn debugger [on/off/quit]: off

Debugger is now off.

Turn debugger [on/off/quit]: quit

*/

Note:  See also Debug_C_Program on TheGeekStuff, as well as debug.txt on the site Advanced_Linux_Programming, Chapter_1.

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DynamicDebugFlags.cpp          download

#include <iostream>

#include <string>

using std::string;

using std::cout;

using std::cin;

using std::endl;

// Debug flags aren't necessarily global:

bool debug = false;

int main(int argc, char* argv[])

{

  for(int i = 0; i < argc; i++)

  {

    if(string(argv[i]) == "--debug=on")

    {

      debug = true;

      break; // out of for()

    }

  }

  bool go = true;

  string reply;

  while(go)

  {

    if(debug)

    {

      // Debugging code here

      cout << "Debugger is now on!" << endl;

    }

    else

    {

      cout << "Debugger is now off." << endl;

    }

    cout << "Turn debugger [on/off/quit]: ";

    cin >> reply;

    if(reply == "on") {debug = true;} // Turn it on

    else if(reply == "off") {debug = false;} // Off

    else if(reply == "quit") {break;} // Out of while(), end program

  }

  return 0;

}

/*

g++ DynamicDebugFlags.cpp -o DynamicDebugFlags

./DynamicDebugFlags

Debugger is now off.

Turn debugger [on/off/quit]: on

Debugger is now on!

Turn debugger [on/off/quit]: off

Debugger is now off.

Turn debugger [on/off/quit]: q

Debugger is now off.

Turn debugger [on/off/quit]: quit

./DynamicDebugFlags --debug=on

Debugger is now on!

Turn debugger [on/off/quit]: q

Debugger is now on!

Turn debugger [on/off/quit]: on

Debugger is now on!

Turn debugger [on/off/quit]: off

Debugger is now off.

Turn debugger [on/off/quit]: quit

*/

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ch3-StringizingExpressions     TCP1, p. 211-212

Contents:     stringizing_expressions.c     StringizingExpressions.cpp

stringizing_expressions.c          download

#include <stdio.h> // for printf()

// print `A' as an int:

#define P(A) printf("%s: %d\n", #A, A) // no semicolon here

int main()

{

  int a = 1, b = 2, c = 3;

  P(a); P(b); P(c); // semicolons

  P(a + b);         // here

  P((c - a)/b);

  return 0;

}

/*

g++ stringizing_expressions.c -o stringizing_expressions

./stringizing_expressions

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

*/

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StringizingExpressions.cpp          download

#include <iostream>

using std::cout;

using std::endl;

#define P(A) cout << #A << ": " << (A) << endl // no semicolon here

int main()

{

  int a = 1, b = 2, c = 3;

  P(a); P(b); P(c); // semicolons

  P(a + b);         // here

  P((c - a)/b);

  return 0;

}

/*

g++ StringizingExpressions.cpp -o StringizingExpressions

./StringizingExpressions

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

*/

Note:  See also PointerArithmetic.cpp in Section ch3-Pointers. 

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Exercise 3-31     TCP1, p. 230     (Conditional debugging)

Exercise 3-31. Modify StringizingExpressions.cpp (see ch3-StringizingExpressions) so that P(A) is conditionally #ifdefed to allow the debugging code to be automatically stripped out by setting a command-line flag. You will need to consult your compiler’s documentation to see how to define and undefine preprocessor values on the compiler command line.

Contents:     cond_debug.c     CondDebug.cpp

cond_debug.c          download

#include <stdio.h> // for printf()

// Conditional debugging:

#ifdef debug

  #define P(A) printf("%s: %d\n", #A, A) // no semicolon here

#else

  #define P(A) // nothing

#endif

int main()

{

  int a = 1, b = 2, c = 3;

  P(a); P(b); P(c); // semicolons

  P(a + b);         // here

  P((c - a)/b);

  return 0;

}

/*

gcc cond_debug.c -o cond_debug

./cond_debug

gcc cond_debug.c -o cond_debug -D debug // define

./cond_debug

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

gcc cond_debug.c -o cond_debug

./cond_debug

gcc cond_debug.c -o cond_debug -D debug=0

./cond_debug

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

gcc cond_debug.c -o cond_debug -U debug // undef

./cond_debug

gcc cond_debug.c -o cond_debug -D debug=1

./cond_debug

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

*/

Note:  See Preprocessor_Options on GCC_online_documentation and Define_macro on SEGGER_Reference_Manual. 

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CondDebug.cpp          download

#include <iostream>

using std::cout;

using std::endl;

// Conditional debugging:

#ifdef debug

  #define P(A) cout << #A << ": " << (A) << endl // no semicolon here

#else

  #define P(A) // nothing

#endif

int main()

{

  int a = 1, b = 2, c = 3;

  P(a); P(b); P(c); // semicolons

  P(a + b);         // here

  P((c - a)/b);

  return 0;

}

/*

g++ CondDebug.cpp -o CondDebug

./CondDebug

g++ CondDebug.cpp -o CondDebug -D debug // define

./CondDebug

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

g++ CondDebug.cpp -o CondDebug

./CondDebug

g++ CondDebug.cpp -o CondDebug -D debug=0

./CondDebug

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

g++ CondDebug.cpp -o CondDebug -U debug // undef

./CondDebug

g++ CondDebug.cpp -o CondDebug -D debug=1

./CondDebug

a: 1

b: 2

c: 3

a + b: 3

(c - a)/b: 1

*/

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ch3-Assert debugging macro in C/C++     TCP1, p. 212

Contents:     assert.c     Assert.cpp

assert.c          download

//#define NDEBUG

#include <assert.h> // for assert() debug macro

int main()

{

  int i = 100;

  assert(i != 100);

  return 0;

}

/*

gcc assert.c -o assert

./assert

assert: assert.c:8: main: Assertion `i != 100' failed.

Aborted (core dumped)

gcc assert.c -o assert -D NDEBUG

./assert

*/

Note:  See also assert.c on the site Advanced_Linux_Programming, Chapter_2, Section ch2-Errors. 

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Assert.cpp          download

//#define NDEBUG

#include <cassert> // for assert() debug macro

int main()

{

  int i = 100;

  assert(i != 100);

  return 0;

}

/*

g++ Assert.cpp -o Assert

./Assert

Assert: Assert.cpp:8: int main(): Assertion `i != 100' failed.

Aborted (core dumped)

g++ Assert.cpp -o Assert -D NDEBUG

./Assert

*/

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