__builtin_inf() functions of GCC compiler - GeeksforGeeks

02 Sep, 2021
These functions do not need to include any header file to use them. So it provides faster usage, as these are Built-in functions of GCC compiler which is most used compiler, even in competitive programming.
Note: If the compiler shows warning of overflow, use casting before __builtin_inf() function as 
(data_type)__builtin_inf()
1. __builtin_inf(void): This function returns positive infinity which will then be converted to DBL_MAX of C language limits.h header file Macro. Its return data type is double. 
Example: 
if __builtin_inf() is used
it returns infinite

Output: inf
Here is a C++ program that shows the use of this function:
C++
#include <iostream>using namespace std; int main(){    // infinite value (<b>inf</b>)    double double_inf = __builtin_inf();     cout << double_inf << endl;    return 0;}
inf
 
2. __builtin_infd32(void): This function returns maximum value of 4-byte integer and returns data type is 32-bit integer.
Example: 
if __builtin_infd32() is used
it returns the maximum value of
the 32-bit integer

Output: 2147483647
Here is a C++ program which shows the use of this function: 
C++
#include <iostream>using namespace std; int main(){    // function returns highest signed integer value    int int_inf = (int)__builtin_infd32();     // you can use __builtin_inf() function    // as well and then cast to integer    int int_inf2 = (int)__builtin_inf();     cout << int_inf << endl;    cout << int_inf2 << endl;     // function returns highest unsigned integer value    unsigned int unsinged_int_inf        = (unsigned int)__builtin_infd32();     // you can use __builtin_inf() function as well    // and then cast to unsigned integer    unsigned int unsinged_int_inf2        = (unsigned int)__builtin_inf();     cout << unsinged_int_inf << endl;    cout << unsinged_int_inf2 << endl;     return 0;}
2147483647
2147483647
4294967295
4294967295
 
3. __builtin_infd64(void): This function returns Highest value that can be represented by 8 byte integer which is highest value of integer we can use in C++.
Example: 
if __builtin_infd64() is used
it returns the maximum value of
the 64-bit integer

Output: 9223372036854775807
Here is a C++ program which shows the use of this function: 
C++
#include <iostream>using namespace std; int main(){    // highest signed 8 byte value    long long int long_inf = (long long int)__builtin_infd64();     // you can use __builtin_inf() as well    // and then cast to long long int    long long int long_inf2        = (long long int)__builtin_inf();     cout << long_inf << endl;    cout << long_inf2 << endl;     // highest unsigned 8 byte value    unsigned long long int unsigned_longlong_inf        = (unsigned long long int)__builtin_infd64();     // you can use __builtin_inf() as well    // and then cast to unsigned long long int    unsigned long long int unsigned_longlong_inf2        = (unsigned long long int)__builtin_inf();     cout << unsigned_longlong_inf << endl;    cout << unsigned_longlong_inf2 << endl;    return 0;}
9223372036854775807
9223372036854775807
18446744073709551615
18446744073709551615
 
4. __builtin_infd128(void): As the maximum size that can be used for integer is 64-bit in C/C++, this function give the same result as __builtin_infd64().
Example: 
if __builtin_infd128() is used
it returns the maximum value of
the 64-bit integer

Output: 9223372036854775807
5. __builtin_inff(void): This function returns float maximum value means 4-byte maximum decimal point value.
Example: 
if __builtin_inff() is used
it returns the maximum value of
the 32-bit float

Output: inf
Here is a C++ program which shows the use of this function: 
C++
#include <iostream>using namespace std; int main(){    float float_inf = __builtin_inff();     // you can use __builtin_inf() as well    // and then cast it to float data type    float float_inf2 = (float)__builtin_inf();     cout << float_inf << endl;    cout << float_inf2 << endl;    return 0;}
inf
inf
 
6. __builtin_infl(void): This function returns maximum long double data type value.
Example: 
if __builtin_infl() is used
it returns the maximum value of
the long double type

Output: inf
Here is a C++ program which shows the use of this function: 
C++
#include <iostream>using namespace std; int main(){    long double long_double_inf = __builtin_infl();     // you can use __builtin_inf() as well    // and then cast it to float data type    long double long_double_inf2        = (long double)__builtin_inf();     cout << long_double_inf << endl;    cout << long_double_inf2 << endl;    return 0;}
inf
inf
 
7. In the recent versions of GCC compiler, these are two new functions: __builtin_infn(void) & __builtin_infnx(void). One can replace n with 32 or 64 and it will return inf value respectively of 32-bit, 64-bit. 
Similar article: Builtin functions of GCC compiler 
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