c-standard-library

#include <cmath> double log(double) {return 1.0;} int main() { log(1.0); } Suppose the function log() in <cmath> is declared in global namespace (this is unspecified in fact, and we just make this assumption), then it refers to the same function as the log() function we defined. So does this code violate the one-definition rule (see here , since no diagnostic required, this code may compile in some compiler and we cannot assert if it is correct)? Note : After recent edits, this is not a duplicate of: What exactly is One Definition Rule in C++? Typical scenario. If extern "C" double log(double)

Seems strncmp is usually recommended than strcmp , what are the advantages? I think it could be related to security. If this is the case, is it still applicable if one of the input string is known to be literal constant, like "LiteralString" ? UPDATE: I mean under the same user scenario where whole strings need to be compared, and strncmp can be used as below. I am wondering it makes sense or not. strncmp(inputString, "LiternalString", strlen("LiternalString")); Surajeet Bharati The problem with strcmp is that sometimes, if by mistake, arguments that are passed are not valid C-strings (meaning

Does anybody know Why argument type of putchar() , fputc() and putc() is not char , but argument type of putwchar() , fputwc() and putwc() is wchar_t ? See also this and this . The answer is 'legacy' (or 'history'). Before the C90 standard, there were no function prototypes and all arguments to all functions were subject to default promotion rules, so a char was automatically passed as an int ( short was promoted to int too, and float to double , and similarly for unsigned types). The standard couldn't afford to break existing code, so it kept that type for these functions. It makes very

What's the difference between using the functions fgetpos() and fsetpos() and using the functions ftell() and fseek() to get and set a position in a file? What are fgetpos() and fsetpos() good for? Why would they be used instead of ftell() and fseek() ? None of the above answers are correct - in fact if you use fsetpos interchangeably with fseek you could introduce a security flaw ( https://www.securecoding.cert.org/confluence/pages/viewpage.action?pageId=20087255 ). The reason is that the fpos_t *pos argument to fsetpos isn't actually an integer so it can't be used to seek to arbitrary

A number of compilers provide 128-bit integer types, but none of the ones I've used provide the typedefs int128_t . Why? As far as I recall, the standard Reserves int128_t for this purpose Encourages implementations that provide such a type to provide the typedef Mandates that such implementations provide an intmax_t of at least 128 bits (and, I do not believe I've used an implementation that actually conforms to that last point) 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

What is the exact difference between the getch and getchar functions? getchar() is a standard function that gets a character from the stdin. getch() is non-standard. It gets a character from the keyboard (which may be different from stdin) and does not echo it. The Standard C function is is getchar() , declared in <stdio.h> . It has existed basically since the dawn of time. It reads one character from standard input ( stdin ), which is typically the user's keyboard, unless it has been redirected (for example via the shell input redirection character < , or a pipe). getch() and getche() are old