Exercise 3-31 (Conditional debugging)

Chapter_3     Exercise_3-30     StringizingExpressions

Assert     Exercise_3-32

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Exercise 3-31     TCP1, p. 230

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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