standards

In std::string there are only const members to fetch the data like c_str(). However I can get a reference to the first element of the string via operator[] and I can write to it. For example, if I have function: void toupper(char *first,char *last_plus_one); I can write directly to vector getting a pointer to the first element: vector<char> message // has "Some Message"; toupper(&message[0],&message[0]+message.size()); Can I do same thing with std::string? string message="Some Message"; toupper(&message[0],&message[0]+message.size()); Does the standard guarantee that the location of the memory

Is !!(x) guaranteed by the standard to return 0/1? Note that I am not asking about c++, where a bool type is defined. Mat Yes, in C99, see §6.5.3.3/4: The result of the logical negation operator ! is 0 if the value of its operand compares unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int . The expression !E is equivalent to (0==E). So !x and !!y can only yield 0 or 1, as int s. For other operators, in C99, see also Is the "true" result of >, <, !, &&, || or == defined? Tim This is a comment really, but it's too long. (Please don't down vote it on that

I had a discussion this morning with a colleague regarding the correctness of a "coding trick" to detect endianness. The trick was: bool is_big_endian() { union { int i; char c[sizeof(int)]; } foo; foo.i = 1; return (foo.c[0] == 1); } To me, it seems that this usage of an union is incorrect because setting one member of the union and reading another is not well-defined. But I have to admit that this is just a feeling and I lack actual proofs to strengthen my point. Is this trick correct ? Who is right here ? Your code is not portable. It might work on some compilers or it might not. You are

I came across the following code recently: class Foo { public: void bar(); // .. other stuff }; void Foo::bar() { if(!this) { // .. do some stuff without accessing any data members return; } // .. do normal actions using data members } The code compiles because in C++ methods are just functions that are implicitly passed a pointer for 'this' and 'this' can be checked to be NULL just like any other pointer. Obviously this code is confusing and bad practice even though it doesn't crash; it would be pretty confusing to step through the code in the debugger, see a NULL pointer is about to have a

So I'm trying to learn more about Denormalized numbers as defined in the IEEE 754 standard for Floating Point numbers. I've already read several articles thanks to Google search results, and I've gone through several StackOverFlow posts. However I still have some questions unanswered. First off, just to review my understanding of what a Denormalized float is: Numbers which have fewer bits of precision, and are smaller (in magnitude) than normalized numbers Essentially, a denormalized float has the ability to represent the SMALLEST (in magnitude) number that is possible to be represented with

Vector's new method data() provides a const and non-const version. However string's data() method only provides a const version. I think they changed the wording about std::string so that the chars are now required to be contiguous (like std::vector ). Was std::string::data just missed? Or is the a good reason to only allow const access to a string's underlying characters? note: std::vector::data has another nice feature, it's not undefined behavior to call data() on an empty vector. Whereas &vec.front() is undefined behavior if it's empty. In C++98/03 there was good reason to not have a non

I have installed mingW to use gcc, platform windows 7. I am trying to locate the standard C library libc.a in mingW folder. no luck.. is it stored in some other name? MinGW does not build against glibc, it builds against msvcrt. As such, it uses libmsvcrtXX.a instead. 来源： https://stackoverflow.com/questions/6394512/standard-c-library-in-mingw