In the C standard, the meaning of the term “reserved” is defined by 7.1.3p2, immediately below the bullet list you are quoting: No other identifiers are reserved. If the program declares or defines an identifier in a context in which it is reserved (other than as allowed by 7.1.4), or defines a reserved identifier as … Read more
According to an excerpt from the book Linux System Programming (by Robert Love), no official sources exist on the etymology of calloc. Some plausible candidates seem to be: Count or counted, because calloc takes a separate count argument. Clear, because it ensures that the returned memory chunk has been cleared. Brian Kernighan is reported to … Read more
I’ll refer to the C standard; I think the C++ standard inherits the rules for <stdint.h> / <cstdint> from C. I know that gcc implements 128-bit signed and unsigned integers, with the names __int128 and unsigned __int128 (__int128 is an implementation-defined keyword) on some platforms. Even for an implementation that provides a standard 128-bit type, … Read more
In C++20 the way that the relational operators work was changed, notably with the introduction of the spaceship <=> operator. In particular, If you only provide operator==, then a != b is rewritten to !(a == b). From [over.match.oper]/3.4: The rewritten candidate set is determined as follows: For the relational ([expr.rel]) operators, the rewritten candidates … Read more
PyCharm is lying to you. The source code you’re looking at is a fake that PyCharm has created. PyCharm knows what functions should be there, and it can guess at their signatures using the function docstrings, but it has no idea what the function bodies should look like. If you want to see the real … Read more
double pow(double, int); hasn’t been removed from the spec. It has simply been reworded. It now lives in [c.math]/p11. How it is computed is an implementation detail. The only C++03 signature that has changed is: float pow(float, int); This now returns double: double pow(float, int); And this change was done for C compatibility. Clarification: 26.8 … Read more
Here is what I have gathered so far: Buffering: If by default the buffer is very small, increasing the buffer size can definitely improve the performance: it reduces the number of HDD hits it reduces the number of system calls Buffer can be set by accessing the underlying streambuf implementation. char Buffer[N]; std::ifstream file(“file.txt”); file.rdbuf()->pubsetbuf(Buffer, … Read more
Because in C variadic function calls, any float argument is promoted (i.e. converted) to a double, so printf is getting a double and would use va_arg(arglist, double) to get it inside its implementation. In the past (C89 and K&R C) every float argument was converted to a double. The current standard omits this promotion for … Read more
Only partially. C++11 <string> has std::to_string for the built-in types: [n3290: 21.5/7]: string to_string(int val); string to_string(unsigned val); string to_string(long val); string to_string(unsigned long val); string to_string(long long val); string to_string(unsigned long long val); string to_string(float val); string to_string(double val); string to_string(long double val); Returns: Each function returns a string object holding the character representation … Read more
It’s the other way around. When ios::ate is set, the initial position will be the end of the file, but you are free to seek thereafter. When ios::app is set, all output operations are performed at the end of the file. Since all writes are implicitly preceded by seeks, there is no way to write … Read more