It’s actually quite common to store a number without needing to know the exact size of the type. There are plenty of quantities in my programs that I can reasonably assume won’t exceed 2 billion, or enforce that they don’t. But that doesn’t mean I need an exact 32 bit type to store them, any … Read more
If you are on windows and using mingw, gcc uses the win32 runtime, where printf needs %I64d for a 64 bit integer. (and %I64u for an unsinged 64 bit integer) For most other platforms you’d use %lld for printing a long long. (and %llu if it’s unsigned). This is standarized in C99. gcc doesn’t come … Read more
That looks like K&R (pre-ANSI) style. I don’t think it’s valid C99, but are they using C99? Joel
No. According to the normative wording of the standard, a definition using empty parentheses without the void keyword is not one of the forms that must be accepted, and strictly speaking the behavior of such a program is undefined. Reference: N1570 section 5.1.2.2.1. (The published 2011 ISO C standard, which is not freely available, has … Read more
The three exceptions where an array does not decay into a pointer are the following: Exception 1. — When the array is the operand of sizeof. int main() { int a[10]; printf(“%zu”, sizeof(a)); /* prints 10 * sizeof(int) */ int* p = a; printf(“%zu”, sizeof(p)); /* prints sizeof(int*) */ } Exception 2. — When the … Read more
glibc uses libnss to support a number of different providers for address resolution services. Unfortunately, you cannot statically link libnss, as exactly what providers it loads depends on the local system’s configuration.
An enum is guaranteed to be represented by an integer, but the actual type (and its signedness) is implementation-dependent. You can force an enumeration to be represented by a signed type by giving one of the enumerators a negative value: enum SignedEnum { a = -1 }; In C++0x, the underlying type of an enumeration … Read more
Use 3 octal digits: char problem[] = “abc\022e”; or split your string: char problem[] = “abc\x12” “e”; Why these work: Unlike hex escapes, standard defines 3 digits as maximum amount for octal escape. 6.4.4.4 Character constants … octal-escape-sequence: \ octal-digit \ octal-digit octal-digit \ octal-digit octal-digit octal-digit … hexadecimal-escape-sequence: \x hexadecimal-digit hexadecimal-escape-sequence hexadecimal-digit String literal … Read more
No, fgets is not actually deprecated in C99 or the current standard, C11. But the author of that tutorial is right that fgets will not stop when it encounters a NUL, and has no mechanism for reporting its reading of such a character. The fgets function reads at most one less than the number of … Read more
It’s undefined behaviour, because it breaks a “shall” constraint: C99 §6.7.5.2: If the size is an expression that is not an integer constant expression… …each time it is evaluated it shall have a value greater than zero.