declaration

来源： https://stackoverflow.com/questions/60600090/c-block-caret-character

来源： https://stackoverflow.com/questions/60600090/c-block-caret-character

问题 This code will compile and is well defined under current C standards: static int foo(int); extern int foo(int); The standard specifies that in this situation ( C11: 6.2.2 Linkages of identifiers (p4) ): For an identifier declared with the storage-class specifier extern in a scope in which a prior declaration of that identifier is visible, 31) if the prior declaration specifies internal or external linkage, the linkage of the identifier at the later declaration is the same as the linkage

问题 The following compiles fine, using static only during declaration of function: #include <stdio.h> static int a(); int a(){ return 5; } int main(){ printf("%d\n", a()); return 0; } As a side note, same behaviour as above happens with inline functions, i.e only the declaration could have the keyword. However the following fails, doing the same but on a variable: #include <stdio.h> static int a; int a = 5; int main(){ printf("%d\n", a); return 0; } Getting thew error: non-static declaration of

问题 The following compiles fine, using static only during declaration of function: #include <stdio.h> static int a(); int a(){ return 5; } int main(){ printf("%d\n", a()); return 0; } As a side note, same behaviour as above happens with inline functions, i.e only the declaration could have the keyword. However the following fails, doing the same but on a variable: #include <stdio.h> static int a; int a = 5; int main(){ printf("%d\n", a); return 0; } Getting thew error: non-static declaration of

问题 In Java, when one declares a string variable the word "String" is capitalized, yet it isn't in any of the other types I've run across (e.g. "int" or "double"). Why is this? Was it just some weird arbitrary decision by the designers? 回答1: Why does is declaration of a string variable in Java capitalized? The String type is capitalized because it is a class , like Object , not a primitive type like boolean or int (the other types you probably ran across). As a class, the String follows the

问题 In Java, when one declares a string variable the word "String" is capitalized, yet it isn't in any of the other types I've run across (e.g. "int" or "double"). Why is this? Was it just some weird arbitrary decision by the designers? 回答1: Why does is declaration of a string variable in Java capitalized? The String type is capitalized because it is a class , like Object , not a primitive type like boolean or int (the other types you probably ran across). As a class, the String follows the

问题 Edit: If it was not clear what I was asking: what are the problems that are mitigated by not allowing nested function declarations? Lambdas work as expected: func main() { inc := func(x int) int { return x+1; } } However, the following declaration inside a declaration is not allowed: func main() { func inc(x int) int { return x+1; } } For what reason are nested functions not allowed? 回答1: I think there are 3 reasons why this obvious feature isn't allowed It would complicate the compiler

问题 There're a lot of questions on SO about details of pointer and array declarations in C (and C subset of C++). I'm more interested in why . Why do we have to put * , [] in front of every variable when we declare several pointers/arrays in a row? int *a, *b; int c[1], d[1]; Why do we have to type out things after/around variable names in function pointers? void (*foo_ptr)(int, int); Why do we have this feature that confuses a lot of newcomers, when even compilers recognize and report these

问题 I tried the following struct mbuf { cacheline: *mut [u64], // great amount of rows follows below // .......... } static mut arr: [mbuf; 32]; // Q1 my main aim // something as before but using Vec; // Q2 also main aim fn main() { // let static mut arr: [mbuf; 32]; // Q3 also doesn't work // static mut arr: [mbuf; 32]; // Q3 also doesn't work } and got error src/main.rs:74:29: 74:30 error: expected one of `+` or `=`, found `;` src/main.rs:74 static mut arr: [mbuf; 32]; ^ Q1,Q2,Q3 - Is it